MFS Series Trust X N-CSR 5 Aug 24 Certified annual shareholder report (management investment company) Financial data

Form N-CSR Cover

Form N-CSR Cover	12 Months Ended
	May 31, 2024
Shareholder Report [Line Items]
Document Type	N-CSR
Amendment Flag	false
Registrant Name	MFS SERIES TRUST X
Entity Central Index Key	0000783740
Document Period End Date	May 31, 2024

Shareholder Report

Shareholder Report	12 Months Ended
	May 31, 2024 USD ($) Holding
Shareholder Report [Line Items]
Document Type	N-CSR
Amendment Flag	false
Registrant Name	MFS SERIES TRUST X
Entity Central Index Key	0000783740
Document Period End Date	May 31, 2024
C000006857 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class C
Trading Symbol	MMACX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 116	[1]
Expense Ratio, Percent	1.09%	[1]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Moderate Allocation Fund (fund) provided a total return of 12.64%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 12.64 % 6.08 % 5.19 % C with CDSC (1% for 12 months) × 11.64 % 6.08 % 5.19 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[2]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006860 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class R1
Trading Symbol	MAMFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 116	[3]
Expense Ratio, Percent	1.09%	[3]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Moderate Allocation Fund (fund) provided a total return of 12.65%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 12.65 % 6.07 % 5.19 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[4]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006863 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class R3
Trading Symbol	MAMHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.34 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 36	[5]
Expense Ratio, Percent	0.34%	[5]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.49%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 13.49 % 6.89 % 5.98 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[6]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006905 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class B
Trading Symbol	MEMBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 2.06 %
Expenses Paid, Amount	$ 216
Expense Ratio, Percent	2.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 10.14%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 10.14 % 0.69 % 0.75 % B with CDSC (declining over six years from 4% to 0%) × 6.14 % 0.30 % 0.75 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[7]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000006907 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging MarketsEquity Fund
Class Name	Class I
Trading Symbol	MEMIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 1.06 %
Expenses Paid, Amount	$ 112
Expense Ratio, Percent	1.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 11.27%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 11.27 % 1.71 % 1.76 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[8]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000006924 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class A
Trading Symbol	MDIDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.35 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 37	[9]
Expense Ratio, Percent	0.35%	[9]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS International Diversification Fund (fund) provided a total return of 14.19%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 14.19 % 7.10 % 5.46 % A with initial sales charge (5.75%) 7.62 % 5.84 % 4.83 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[10]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006930 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class C
Trading Symbol	MDIGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 117	[11]
Expense Ratio, Percent	1.10%	[11]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS International Diversification Fund (fund) provided a total return of 13.30%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 13.30 % 6.30 % 4.67 % C with CDSC (1% for 12 months) × 12.30 % 6.30 % 4.67 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[12]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006942 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class B
Trading Symbol	MGIBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.81 %
Expenses Paid, Amount	$ 197
Expense Ratio, Percent	1.81%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 18.19%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 18.19 % * 7.20 % 6.52 % B with CDSC (declining over six years from 4% to 0%) × 14.19 % * 6.91 % 6.52 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.16%. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[13]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000034484 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class R6
Trading Symbol	MGRDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.72 %
Expenses Paid, Amount	$ 77
Expense Ratio, Percent	0.72%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS International Growth Fund (fund) provided a total return of 12.50%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R6 without sales charge 12.50 % 8.61 % 6.82 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[14]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000142782 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class R4
Trading Symbol	MNWUX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.68 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 71	[15]
Expense Ratio, Percent	0.68%	[15]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class R4 shares of the fund provided a total return of 9.01%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* R4 without sales charge 9.01 % 3.11 % 3.08 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[16]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160020 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class A
Trading Symbol	BRWAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.74 %
Expenses Paid, Amount	$ 88
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 38.18%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* A without sales charge 38.18 % 17.84 % 14.66 % A with initial sales charge (5.75%) 30.23 % 16.45 % 13.88 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[17]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160035 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class R3
Trading Symbol	BRSTX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.99 %
Expenses Paid, Amount	$ 110
Expense Ratio, Percent	0.99%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.45%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R3 without sales charge 21.45 % 7.55 % 8.46 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[18]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160037 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class R6
Trading Symbol	BRSYX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.64 %
Expenses Paid, Amount	$ 71
Expense Ratio, Percent	0.64%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.83%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 21.83 % 7.93 % 8.83 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[19]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000172720 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class R2
Trading Symbol	BMSSX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.09 %
Expenses Paid, Amount	$ 126
Expense Ratio, Percent	1.09%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 31.24%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R2 without sales charge 31.24 % 12.33 % 10.75 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[20]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000172722 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class R4
Trading Symbol	BMSVX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.59 %
Expenses Paid, Amount	$ 68
Expense Ratio, Percent	0.59%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 31.93%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R4 without sales charge 31.93 % 12.90 % 11.31 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[21]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000006845 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class I
Trading Symbol	MIAGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.13 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 14	[22]
Expense Ratio, Percent	0.13%	[22]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 20.32%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 20.32 % 10.47 % 8.79 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[23]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006850 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class R3
Trading Symbol	MAAHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.38 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 42	[24]
Expense Ratio, Percent	0.38%	[24]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.98%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 19.98 % 10.19 % 8.52 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[25]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006893 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class C
Trading Symbol	MACVX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 114	[26]
Expense Ratio, Percent	1.09%	[26]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Conservative Allocation Fund (fund) provided a total return of 9.24%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 9.24 % 4.25 ) % 3.79 % C with CDSC (1% for 12 months) × 8.24 % 4.25 ) % 3.79 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[27]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006894 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class I
Trading Symbol	MACIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 9	[28]
Expense Ratio, Percent	0.09%	[28]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Conservative Allocation Fund (fund) provided a total return of 10.34%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 10.34 % 5.30 ) % 4.83 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[29]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006917 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class C
Trading Symbol	MCGWX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 119	[30]
Expense Ratio, Percent	1.10%	[30]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Growth Allocation Fund (fund) provided a total return of 16.45%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 16.45 % 7.96 % 6.60 % C with CDSC (1% for 12 months) × 15.45 % 7.96 % 6.60 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[31]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006918 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class I
Trading Symbol	MGWIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 11	[32]
Expense Ratio, Percent	0.10%	[32]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.60%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 17.60 % 9.05 % 7.67 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[33]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006939 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class C
Trading Symbol	MGRCX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.85 %
Expenses Paid, Amount	$ 195
Expense Ratio, Percent	1.85%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS International Growth Fund (fund) provided a total return of 11.24%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 11.24 % 7.40 % 5.65 % C with CDSC (1% for 12 months) × 10.24 % 7.40 % 5.65 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[34]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000034485 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class R6
Trading Symbol	MINJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.69 %
Expenses Paid, Amount	$ 76
Expense Ratio, Percent	0.69%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 19.51%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R6 without sales charge 19.51 % * 8.40 % 7.70 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.48%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[35]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000071437 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class R4
Trading Symbol	MINHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.80 %
Expenses Paid, Amount	$ 88
Expense Ratio, Percent	0.80%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 19.41%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 19.41 % * 8.28 % 7.59 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.38%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[36]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000160027 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class R4
Trading Symbol	BRWUX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.49 %
Expenses Paid, Amount	$ 58
Expense Ratio, Percent	0.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 38.51%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R4 without sales charge 38.51 % 18.15 % 14.96 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[37]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160028 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class R6
Trading Symbol	BRWVX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.42 %
Expenses Paid, Amount	$ 50
Expense Ratio, Percent	0.42%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 38.63%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 38.63 % 18.25 % 15.05 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[38]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160042 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class R1
Trading Symbol	BRUJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 0.74 % For the period from June 1, 2023 through May 31, 2024, the distribution fee was not imposed. Had the distribution fee been imposed throughout the entire period, the “Costs of a $10,000 investment” and the “Costs paid as a percentage of a $10,000 investment” would have been approximately $169 and 1.49%, respectively.
Expenses Paid, Amount	$ 84
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.00%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R1 without sales charge 27.00 % 11.70 % 9.73 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[39]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000160045 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class R4
Trading Symbol	BRUMX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.49 %
Expenses Paid, Amount	$ 56
Expense Ratio, Percent	0.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.30%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R4 without sales charge 27.30 % 12.31 % 10.55 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[40]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000160046 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class R6
Trading Symbol	BRUNX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.42 %
Expenses Paid, Amount	$ 48
Expense Ratio, Percent	0.42%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.34%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 27.34 % 12.40 % 10.63 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[41]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000195683 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class R6
Trading Symbol	MDIZX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.00 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 0	[42]
Expense Ratio, Percent	0%	[42]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS International Diversification Fund (fund) provided a total return of 14.58%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 14.58 % 7.47 % 6.18 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.51 % * For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2024. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[43]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000220110 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class R1
Trading Symbol	MKVDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.73 %
Expenses Paid, Amount	$ 188
Expense Ratio, Percent	1.73%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS International Large Cap Value Fund (fund) provided a total return of 16.98%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R1 without sales charge 16.98 % 11.18 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[44]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000220113 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class R2
Trading Symbol	MKVEX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.23 %
Expenses Paid, Amount	$ 134
Expense Ratio, Percent	1.23%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS International Large Cap Value Fund (fund) provided a total return of 17.56%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R2 without sales charge 17.56 % 11.71 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[45]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000006856 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class B
Trading Symbol	MMABX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 116	[46]
Expense Ratio, Percent	1.09%	[46]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Moderate Allocation Fund (fund) provided a total return of 12.67%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 12.67 % 6.09 % 5.20 % B with CDSC (declining over six years from 4% to 0%) × 8.67 % 5.77 % 5.20 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[47]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006899 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class R3
Trading Symbol	MACNX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.34 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 36	[48]
Expense Ratio, Percent	0.34%	[48]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Conservative Allocation Fund (fund) provided a total return of 10.01%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 10.01 % 5.03 ) % 4.56 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[49]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006923 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class R3
Trading Symbol	MAGEX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.35 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 38	[50]
Expense Ratio, Percent	0.35%	[50]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.33%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 17.33 % 8.78 % 7.40 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[51]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006933 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class R1
Trading Symbol	MDIOX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 117	[52]
Expense Ratio, Percent	1.10%	[52]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS International Diversification Fund (fund) provided a total return of 13.25%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 13.25 % 6.29 % 4.67 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[53]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000071428 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class R6
Trading Symbol	MEMJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.90 %
Expenses Paid, Amount	$ 95
Expense Ratio, Percent	0.90%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 11.45%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R6 without sales charge 11.45 % 1.85 % 1.89 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[54]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000071433 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class R3
Trading Symbol	MGRTX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 1.09 %
Expenses Paid, Amount	$ 116
Expense Ratio, Percent	1.09%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS International Growth Fund (fund) provided a total return of 12.09%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 12.09 % 8.21 % 6.44 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[55]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000071434 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class R1
Trading Symbol	MINRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.80 %
Expenses Paid, Amount	$ 196
Expense Ratio, Percent	1.80%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 18.22%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 18.22 % 7.20 % 6.52 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[56]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000142777 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class C
Trading Symbol	MNWCX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.68 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 175	[57]
Expense Ratio, Percent	1.68%	[57]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class C shares of the fund provided a total return of 7.99%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* C without sales charge 7.99 % 2.08 % 2.06 % C with CDSC (1% for 12 months) × 6.99 % 2.08 % 2.06 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[58]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160024 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class R1
Trading Symbol	BRWRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.49 %
Expenses Paid, Amount	$ 177
Expense Ratio, Percent	1.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 37.16%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R1 without sales charge 37.16 % 16.96 % 13.81 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[59]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160031 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class C
Trading Symbol	BRSHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.74 %
Expenses Paid, Amount	$ 192
Expense Ratio, Percent	1.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 20.60%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* C without sales charge 20.60 % 6.76 % 7.66 % C with CDSC (1% for 12 months) × 19.60 % 6.76 % 7.66 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[60]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160038 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class A
Trading Symbol	BRUDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.74 %
Expenses Paid, Amount	$ 84
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.03%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* A without sales charge 27.03 % 12.03 % 10.27 % A with initial sales charge (5.75%) 19.72 % 10.72 % 9.52 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[61]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000172717 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class C
Trading Symbol	BMSDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.59 %
Expenses Paid, Amount	$ 183
Expense Ratio, Percent	1.59%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 30.59%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* C without sales charge 30.59 % 11.77 % 10.20 % C with CDSC (1% for 12 months) × 29.59 % 11.77 % 10.20 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[62]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000220106 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class R6
Trading Symbol	MKVHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.67 %
Expenses Paid, Amount	$ 73
Expense Ratio, Percent	0.67%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS International Large Cap Value Fund (fund) provided a total return of 18.24%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R6 without sales charge 18.24 % 12.37 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[63]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000220109 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class A
Trading Symbol	MKVBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.98 %
Expenses Paid, Amount	$ 107
Expense Ratio, Percent	0.98%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS International Large Cap Value Fund (fund) provided a total return of 17.92%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* A without sales charge 17.92 % 12.05 % A with initial sales charge (5.75%) 11.14 % 10.37 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[64]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000231059 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class R6
Trading Symbol	MAMPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.02 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 2	[65]
Expense Ratio, Percent	0.02%	[65]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.87%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R6 without sales charge 13.87 % 1.36 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 9.13 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 2.89 % * For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[66]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006838 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class A
Trading Symbol	MAAGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.38 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 42	[67]
Expense Ratio, Percent	0.38%	[67]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.97%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 19.97 % 10.20 % 8.53 % A with initial sales charge (5.75%) 13.07 % 8.90 % 7.89 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[68]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006839 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class R4
Trading Symbol	MAALX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.13 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 14	[69]
Expense Ratio, Percent	0.13%	[69]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 20.26%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 20.26 % 10.47 % 8.79 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[70]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006844 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class C
Trading Symbol	MCAGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ C $ 1.13 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 124	[71]
Expense Ratio, Percent	1.13%	[71]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.11%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 19.11 % 9.37 % 7.71 % C with CDSC (1% for 12 months) × 18.11 % 9.37 % 7.71 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[72]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006851 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class A
Trading Symbol	MAMAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.34 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 36	[73]
Expense Ratio, Percent	0.34%	[73]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.48%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 13.48 % 6.87 % 5.98 % A with initial sales charge (5.75%) 6.95 % 5.61 % 5.36 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[74]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006912 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class R4
Trading Symbol	MAGJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 11	[75]
Expense Ratio, Percent	0.10%	[75]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.59%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 17.59 % 9.06 % 7.67 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[76]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006922 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class R2
Trading Symbol	MGALX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 0.60 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 65	[77]
Expense Ratio, Percent	0.60%	[77]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.00%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 17.00 % 8.51 % 7.14 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[78]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006944 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class I
Trading Symbol	MINIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.80 %
Expenses Paid, Amount	$ 88
Expense Ratio, Percent	0.80%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 19.41%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 19.41 % * 8.28 % 7.59 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.38%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[79]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000071425 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class R2
Trading Symbol	MEMFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.56 %
Expenses Paid, Amount	$ 164
Expense Ratio, Percent	1.56%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 10.71%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 10.71 % 1.20 % 1.25 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[80]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000071427 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class R4
Trading Symbol	MEMHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 1.06 %
Expenses Paid, Amount	$ 112
Expense Ratio, Percent	1.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 11.27%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 11.27 % 1.71 % 1.76 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[81]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000071435 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class R2
Trading Symbol	MINFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.30 %
Expenses Paid, Amount	$ 142
Expense Ratio, Percent	1.30%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 18.79%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 18.79 % * 7.74 % 7.05 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.75%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[82]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000142778 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class I
Trading Symbol	MNWIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.69 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 72	[83]
Expense Ratio, Percent	0.69%	[83]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class I shares of the fund provided a total return of 9.01%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* I without sales charge 9.01 % 3.09 % 3.08 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[84]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000142780 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class R2
Trading Symbol	MNWSX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 1.18 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 123	[85]
Expense Ratio, Percent	1.18%	[85]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class R2 shares of the fund provided a total return of 8.53%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* R2 without sales charge 8.53 % 2.60 % 2.58 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[86]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160039 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class B
Trading Symbol	BRUEX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.49 %
Expenses Paid, Amount	$ 168
Expense Ratio, Percent	1.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 26.05%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* B without sales charge 26.05 % 11.17 % 9.44 % B with CDSC (declining over six years from 4% to 0%) × 22.05 % 10.91 % 9.44 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[87]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000160041 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class I
Trading Symbol	BRUHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.49 %
Expenses Paid, Amount	$ 56
Expense Ratio, Percent	0.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.34%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* I without sales charge 27.34 % 12.30 % 10.54 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[88]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000172716 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class B
Trading Symbol	BMSBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.59 %
Expenses Paid, Amount	$ 183
Expense Ratio, Percent	1.59%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 30.58%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* B without sales charge 30.58 % 11.78 % 10.20 % B with CDSC (declining over six years from 4% to 0%) × 26.58 % 11.52 % 10.20 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[89]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000172718 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class I
Trading Symbol	BMSLX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.59 %
Expenses Paid, Amount	$ 68
Expense Ratio, Percent	0.59%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 31.91%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* I without sales charge 31.91 % 12.90 % 11.31 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[90]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000006858 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class I
Trading Symbol	MMAIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 10	[91]
Expense Ratio, Percent	0.09%	[91]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.79%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 13.79 % 7.15 % 6.25 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[92]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006862 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class R2
Trading Symbol	MARRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 0.59 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 63	[93]
Expense Ratio, Percent	0.59%	[93]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.22%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 13.22 % 6.61 % 5.72 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[94]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006906 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class C
Trading Symbol	MEMCX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 2.06 %
Expenses Paid, Amount	$ 216
Expense Ratio, Percent	2.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 10.11%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 10.11 % 0.69 % 0.75 % C with CDSC (1% for 12 months) × 9.11 % 0.69 % 0.75 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[95]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000006929 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class B
Trading Symbol	MDIFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 117	[96]
Expense Ratio, Percent	1.10%	[96]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS International Diversification Fund (fund) provided a total return of 13.32%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 13.32 % 6.31 % 4.67 % B with CDSC (declining over six years from 4% to 0%) × 9.32 % 5.99 % 4.67 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[97]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006931 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class I
Trading Symbol	MDIJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ I $ 0.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 11	[98]
Expense Ratio, Percent	0.10%	[98]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS International Diversification Fund (fund) provided a total return of 14.48%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 14.48 % 7.37 % 5.72 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[99]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006941 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class A
Trading Symbol	MGIAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 1.05 %
Expenses Paid, Amount	$ 115
Expense Ratio, Percent	1.05%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 19.12%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 19.12 % * 8.01 % 7.32 % A with initial sales charge (5.75%) 12.27 % * 6.74 % 6.69 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.09%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[100]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000006943 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class C
Trading Symbol	MGICX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.81 %
Expenses Paid, Amount	$ 197
Expense Ratio, Percent	1.81%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 18.22%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 18.22 % * 7.21 % 6.52 % C with CDSC (1% for 12 months) × 17.22 % * 7.21 % 6.52 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.19%. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[101]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000071424 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class R
Trading Symbol	MEMRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 2.06 %
Expenses Paid, Amount	$ 216
Expense Ratio, Percent	2.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 10.17%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 10.17 % 0.71 % 0.75 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[102]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000142781 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class R3
Trading Symbol	MNWTX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.93 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 97	[103]
Expense Ratio, Percent	0.93%	[103]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class R3 shares of the fund provided a total return of 8.79%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* R3 without sales charge 8.79 % 2.85 % 2.83 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[104]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %	[105]
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160034 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class R2
Trading Symbol	BRSSX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.24 %
Expenses Paid, Amount	$ 137
Expense Ratio, Percent	1.24%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.11%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R2 without sales charge 21.11 % 7.29 % 8.19 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[106]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160036 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class R4
Trading Symbol	BRSUX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.74 %
Expenses Paid, Amount	$ 82
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.76%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R4 without sales charge 21.76 % 7.83 % 8.73 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[107]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000172719 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class R1
Trading Symbol	BMSRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.59 %
Expenses Paid, Amount	$ 183
Expense Ratio, Percent	1.59%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 30.52%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R1 without sales charge 30.52 % 11.78 % 10.19 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[108]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000172721 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class R3
Trading Symbol	BMSTX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.84 %
Expenses Paid, Amount	$ 97
Expense Ratio, Percent	0.84%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 31.54%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R3 without sales charge 31.54 % 12.62 % 11.03 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[109]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000195688 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class R6
Trading Symbol	MNWZX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.62 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 65	[110]
Expense Ratio, Percent	0.62%	[110]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class R6 shares of the fund provided a total return of 9.18%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 9.18 % 3.19 % 3.66 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 13.68 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 2.06 % * For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[111]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000006847 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class R1
Trading Symbol	MAAFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.13 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 124	[112]
Expense Ratio, Percent	1.13%	[112]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.08%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 19.08 % 9.37 % 7.71 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[113]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006849 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class R2
Trading Symbol	MAWAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 0.63 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 69	[114]
Expense Ratio, Percent	0.63%	[114]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.66%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 19.66 % 9.92 % 8.25 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[115]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006896 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class R1
Trading Symbol	MACKX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 114	[116]
Expense Ratio, Percent	1.09%	[116]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Conservative Allocation Fund (fund) provided a total return of 9.28%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 9.28 % 4.25 ) % 3.79 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[117]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006898 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class R2
Trading Symbol	MCARX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 0.59 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 62	[118]
Expense Ratio, Percent	0.59%	[118]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Conservative Allocation Fund (fund) provided a total return of 9.73%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 9.73 % 4.77 ) % 4.30 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[119]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006911 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class A
Trading Symbol	MAGWX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.35 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 38	[120]
Expense Ratio, Percent	0.35%	[120]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.32%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 17.32 % 8.78 % 7.40 % A with initial sales charge (5.75%) 10.57 % 7.50 % 6.77 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[121]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006916 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class B
Trading Symbol	MBGWX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 119	[122]
Expense Ratio, Percent	1.10%	[122]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Growth Allocation Fund (fund) provided a total return of 16.42%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 16.42 % 7.96 % 6.60 % B with CDSC (declining over six years from 4% to 0%) × 12.42 % 7.66 % 6.60 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[123]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006920 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class R1
Trading Symbol	MAGMX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 119	[124]
Expense Ratio, Percent	1.10%	[124]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Growth Allocation Fund (fund) provided a total return of 16.46%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 16.46 % 7.96 % 6.60 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 10.24 % 7.95 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[125]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006937 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class A
Trading Symbol	MGRAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 1.09 %
Expenses Paid, Amount	$ 116
Expense Ratio, Percent	1.09%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS International Growth Fund (fund) provided a total return of 12.11%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 12.11 % 8.22 % 6.44 % A with initial sales charge (5.75%) 5.66 % 6.94 % 5.81 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[126]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000006938 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class B
Trading Symbol	MGRBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.85 %
Expenses Paid, Amount	$ 195
Expense Ratio, Percent	1.85%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS International Growth Fund (fund) provided a total return of 11.25%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 11.25 % 7.40 % 5.65 % B with CDSC (declining over six years from 4% to 0%) × 7.25 % 7.10 % 5.65 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[127]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000142775 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class A
Trading Symbol	MNWAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.93 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 97	[128]
Expense Ratio, Percent	0.93%	[128]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class A shares of the fund provided a total return of 8.78%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* A without sales charge 8.78 % 2.91 % 2.93 % A with initial sales charge (5.75%) 2.52 % 1.70 % 2.32 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[129]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000142776 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class B
Trading Symbol	MNWBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.68 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 175	[130]
Expense Ratio, Percent	1.68%	[130]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class B shares of the fund provided a total return of 7.95%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* B without sales charge 7.95 % 2.09 % 2.06 % B with CDSC (declining over six years from 4% to 0%) × 3.95 % 1.72 % 2.06 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[131]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160026 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class R3
Trading Symbol	BRWTX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.74 %
Expenses Paid, Amount	$ 88
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 38.22%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R3 without sales charge 38.22 % 17.85 % 14.67 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[132]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160029 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class A
Trading Symbol	BRSDX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.99 %
Expenses Paid, Amount	$ 110
Expense Ratio, Percent	0.99%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.38%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* A without sales charge 21.38 % 7.56 % 8.47 % A with initial sales charge (5.75%) 14.40 % 6.29 % 7.74 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[133]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160043 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class R2
Trading Symbol	BRUKX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 0.99 %
Expenses Paid, Amount	$ 112
Expense Ratio, Percent	0.99%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 26.70%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R2 without sales charge 26.70 % 11.75 % 9.99 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[134]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000160044 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class R3
Trading Symbol	BRULX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.74 %
Expenses Paid, Amount	$ 84
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 27.01%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R3 without sales charge 27.01 % 12.03 % 10.27 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[135]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
C000220107 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class R4
Trading Symbol	MKVGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.73 %
Expenses Paid, Amount	$ 80
Expense Ratio, Percent	0.73%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS International Large Cap Value Fund (fund) provided a total return of 18.15%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R4 without sales charge 18.15 % 12.36 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[136]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000220108 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class R3
Trading Symbol	MKVFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.98 %
Expenses Paid, Amount	$ 107
Expense Ratio, Percent	0.98%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS International Large Cap Value Fund (fund) provided a total return of 17.89%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R3 without sales charge 17.89 % 12.05 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[137]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000006843 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class B
Trading Symbol	MBAGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.13 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 124	[138]
Expense Ratio, Percent	1.13%	[138]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 19.06%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 19.06 % 9.37 % 7.71 % B with CDSC (declining over six years from 4% to 0%) × 15.06 % 9.09 % 7.71 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 12.36 % 9.10 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[139]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006892 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class B
Trading Symbol	MACBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ B $ 1.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 114	[140]
Expense Ratio, Percent	1.09%	[140]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Conservative Allocation Fund (fund) provided a total return of 9.18%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 9.18 % 4.25 ) % 3.78 % B with CDSC (declining over six years from 4% to 0%) × 5.18 % 3.91 ) % 3.78 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[141]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006936 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class R3
Trading Symbol	MDIHX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R3 $ 0.35 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 37	[142]
Expense Ratio, Percent	0.35%	[142]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS International Diversification Fund (fund) provided a total return of 14.19%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 14.19 % 7.10 % 5.46 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[143]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000071426 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class R3
Trading Symbol	MEMGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 1.31 %
Expenses Paid, Amount	$ 138
Expense Ratio, Percent	1.31%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 11.01%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 11.01 % 1.46 % 1.51 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[144]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000071431 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class R1
Trading Symbol	MGRRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.84 %
Expenses Paid, Amount	$ 194
Expense Ratio, Percent	1.84%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS International Growth Fund (fund) provided a total return of 11.25%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 11.25 % 7.40 % 5.65 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[145]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000071436 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Intrinsic Value Fund
Class Name	Class R3
Trading Symbol	MINGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Intrinsic Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 1.06 %
Expenses Paid, Amount	$ 116
Expense Ratio, Percent	1.06%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R3 shares of the MFS International Intrinsic Value Fund (fund) provided a total return of 19.12%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Index Stock selection within both the financials and real estate sectors. An underweight position in the consumer discretionary sector. Top detractors from performance relative to the MSCI EAFE Index An overweight position in the consumer staples sector. Stock selection within the health care sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R3 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 19.12 % * 8.01 % 7.32 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 18.53 % * 8.05 % 4.60 % ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.09%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r3
Net Assets	$ 22,083,354,936
Holdings Count | Holding	93
Advisory Fees Paid, Amount	$ 136,782,215	[146]
Investment Company Portfolio Turnover	12%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 22,083,354,936 Total Management Fee ($)#: 136,782,215 Total Number of Holdings: 93 Portfolio Turnover (%): 12 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.1 % Money Market Funds 2.9 % Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 % Issuer country weightings France 17.4 % United Kingdom 14.0 % Japan 13.9 % United States 10.1 % Germany 9.2 % Switzerland 7.1 % Ireland 4.9 % Canada 4.7 % Spain 4.3 % Other Countries 14.4 %
Largest Holdings [Text Block]	Top ten holdings Schneider Electric SE 3.4 % TotalEnergies SE 3.2 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 2.8 % Franco-Nevada Corp. 2.8 % Cadence Design Systems, Inc. 2.7 % Legrand S.A. 2.6 % NatWest Group PLC 2.4 % AIB Group PLC 2.4 % Resona Holdings, Inc. 2.2 % CaixaBank S.A. 2.2 %
C000142779 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Managed Wealth Fund
Class Name	Class R1
Trading Symbol	MNWRX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Managed Wealth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R1 $ 1.68 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 175	[147]
Expense Ratio, Percent	1.68%	[147]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE The MFS Managed Wealth Fund's (fund) investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to three MFS equity funds, referred to as underlying funds, and (2) a tactical asset allocation overlay primarily using derivative instruments to seek to decrease the volatility of the fund’s returns by reducing the fund’s exposure to the equity and/or currency markets as represented by the underlying funds and also to potentially expose the fund to asset classes and/or markets in which the underlying funds have little or no exposure. In addition, MFS may seek to limit the fund’s exposure to certain extreme market events. It is expected that the fund will generally have lower volatility than the overall equity market and will generally underperform the equity markets during periods of rising equity markets. A committee of portfolio managers (committee) is responsible for selecting the underlying funds, determining the target strategic allocations to the underlying funds, and determining the fund’s tactical allocation overlay. For the twelve months ended May 31, 2024, Class R1 shares of the fund provided a total return of 7.95%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the ICE BofA 0-3 Month U.S. Treasury Bill Index, generated a return of 5.50%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to absolute performance The fund's allocation to both the MFS Growth Fund and the MFS Value Fund. Top detractors from absolute performance The fund's short exposure to futures contracts on both the Russell 1000® Growth Index and Russell 1000® Value Index.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes corresponds to the fund’s investment strategies, over the same periods. Share Class 1-yr 5-yr Life* R1 without sales charge 7.95 % 2.09 % 2.06 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 28.19 % 15.80 % 12.56 % ICE BofA 0-3 Month U.S. Treasury Bill Index +∆ 5.50 % 2.12 % 1.46 % * For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024. + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 39,198,042
Holdings Count | Holding	14
Advisory Fees Paid, Amount	$ 160,166	[148]
Investment Company Portfolio Turnover	6%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 39,198,042 Total Management Fee ($)#: 160,166 Total Number of Holdings: 14 Portfolio Turnover (%): 6 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 5/31/24) Portfolio structure Active Derivative Net Market Strategic Allocation MFS Institutional International Equity Fund 30.4 % MFS Growth Fund 30.4 % MFS Value Fund 30.2 % Market Exposure Overlay Mini Russell 1000 Value Index Future JUN 21 24 (19.3 ) % Mini MSCI EAFE Index Future JUN 21 24 (19.7 ) % Mini Russell 1000 Growth Future JUN 21 24 (20.7 ) % Net Equity Exposure 31.3 ) % Standard & Poor's 500 Index Option 4200.00 PUT SEP 20 24 (0.2 ) % Standard & Poor's 500 Index Option 4200.00 PUT DEC 20 24 (0.3 ) % Standard & Poor’s 500 Index Option 4700.00 PUT SEP 20 24 (0.5 ) % Standard & Poor's 500 Index Option 4400.00 PUT DEC 20 24 (0.5 ) % Standard & Poors Index Option PUT(s) (1.5 ) % Downside Hedge(s) (1.5 ) % Net Equivalent Equity Exposure 91.0 % (61.2 ) % 29.8 ) % Limited Maturity U.S. Treasury Notes 3.0 ) % Cash Cash & Cash Equivalents (d) 5.9 ) % Other (e) 61.3 ) % Total Net Exposure Summary 100.0 ) %
Exposure Basis Explanation [Text Block]	(a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.
C000160022 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class C
Trading Symbol	BRWCX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.49 %
Expenses Paid, Amount	$ 177
Expense Ratio, Percent	1.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 37.16%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* C without sales charge 37.16 % 16.98 % 13.81 % C with CDSC (1% for 12 months) × 36.16 % 16.98 % 13.81 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[149]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160033 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class R1
Trading Symbol	BRSPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R1 $ 1.74 %
Expenses Paid, Amount	$ 192
Expense Ratio, Percent	1.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R1 shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 20.58%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R1 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R1 without sales charge 20.58 % 6.76 % 7.66 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r1
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[150]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160040 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Value Equity Fund
Class Name	Class C
Trading Symbol	BRUGX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Value Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.49 %
Expenses Paid, Amount	$ 168
Expense Ratio, Percent	1.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS Blended Research Value Equity Fund (fund) provided a total return of 25.97%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Value Index, generated a return of 21.71%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Value Index Stock selection within the information technology, utilities, financials and energy sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell 1000® Value Index Security selection within both the industrials and consumer staples sectors weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* C without sales charge 25.97 % 11.19 % 9.44 % C with CDSC (1% for 12 months) × 24.97 % 11.19 % 9.44 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Value Index +∆ 21.71 % 10.74 % 10.06 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 297,554,041
Holdings Count | Holding	110
Advisory Fees Paid, Amount	$ 1,035,469	[151]
Investment Company Portfolio Turnover	55%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 297,554,041 Total Management Fee ($)#: 1,035,469 Total Number of Holdings: 110 Portfolio Turnover (%): 55 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.5 % Money Market Funds 1.5 % GICS equity sectors Financials 22.8 % Health Care 14.3 % Industrials 13.2 % Energy 8.3 % Information Technology 8.3 % Consumer Staples 7.3 % Utilities 5.8 % Communication Services 5.1 % Real Estate 5.1 % Consumer Discretionary 4.3 % Materials 4.0 % Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings JPMorgan Chase & Co. 3.6 % Johnson & Johnson 2.7 % Wells Fargo & Co. 2.4 % Pfizer, Inc. 2.0 % Berkshire Hathaway, Inc., "B" 2.0 % Cigna Group 1.8 % Eaton Corp. PLC 1.7 % American Express Co. 1.7 % Applied Materials, Inc. 1.7 % McKesson Corp. 1.7 %
C000172715 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Mid Cap Equity Fund
Class Name	Class A
Trading Symbol	BMSFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.84 %
Expenses Paid, Amount	$ 97
Expense Ratio, Percent	0.84%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 31.49%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* A without sales charge 31.49 % 12.61 % 11.03 % A with initial sales charge (5.75%) 23.93 % 11.28 % 10.18 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[152]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000220111 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class I
Trading Symbol	MKVIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.72 %
Expenses Paid, Amount	$ 79
Expense Ratio, Percent	0.72%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS International Large Cap Value Fund (fund) provided a total return of 18.16%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* I without sales charge 18.16 % 12.35 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[153]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
C000231058 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Aggressive Growth Allocation Fund
Class Name	Class R6
Trading Symbol	AGGPX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Aggressive Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.05 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 6	[154]
Expense Ratio, Percent	0.05%	[154]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Aggressive Growth Allocation Fund (fund) provided a total return of 20.37%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Aggressive Growth Allocation Fund Blended Index (Blended Index), generated a return of 23.36%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the US equity segment, the fund's exposure to, and relative performance of, the MFS Growth Fund contributed to relative results. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of both the MFS Research International Fund and MFS International Large Cap Value Fund held back the results as both funds lagged their respective benchmarks.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R6 without sales charge 20.37 % 3.53 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 9.13 % MFS Aggressive Growth Allocation Fund Blended Index ∆ 23.36 % 6.83 % * For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024. ∆ Source: FactSet Research Systems Inc.
Performance Inception Date	May 31, 2024
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 2,792,680,875
Holdings Count | Holding	16
Advisory Fees Paid, Amount	$ 0	[155]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	Net Assets ($): 2,792,680,875 Total Management Fee ($)#: 0 Total Number of Holdings: 16 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 12.0 % MFS Growth Fund 11.3 % MFS Research Fund 10.3 % MFS Mid Cap Value Fund 10.1 % MFS Mid Cap Growth Fund 9.8 % MFS Research International Fund 8.1 % MFS International Large Cap Value Fund 5.1 % MFS International Intrinsic Value Fund 5.0 % MFS International Growth Fund 5.0 % MFS Commodity Strategy Fund 5.0 % MFS Global Real Estate Fund 4.9 % MFS International New Discovery Fund 4.0 % MFS Emerging Markets Equity Fund 3.0 % MFS New Discovery Value Fund 2.5 % MFS New Discovery Fund 2.5 % MFS Institutional Money Market Portfolio 1.4 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000231060 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class R6
Trading Symbol	MACQX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.03 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 3	[156]
Expense Ratio, Percent	0.03%	[156]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Conservative Allocation Fund (fund) provided a total return of 10.41%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R6 without sales charge 10.41 % 0.53 ) % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (3.74 ) % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 0.73 ) % * For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[157]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000231061 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Growth Allocation Fund
Class Name	Class R6
Trading Symbol	MAGQX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Growth Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R6 $ 0.02 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 2	[158]
Expense Ratio, Percent	0.02%	[158]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Growth Allocation Fund (fund) provided a total return of 17.73%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Growth Allocation Fund Blended Index (Blended Index), generated a return of 19.07%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund bolstered relative returns as the fund outperformed its respective benchmark. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* R6 without sales charge 17.73 % 2.70 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 9.13 % MFS Growth Allocation Fund Blended Index ∆ 19.07 % 4.93 % * For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 6,542,423,898
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[159]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,542,423,898 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Value Fund 10.1 % MFS Growth Fund 9.4 % MFS Research Fund 9.3 % MFS Mid Cap Value Fund 9.1 % MFS Mid Cap Growth Fund 8.8 % MFS Research International Fund 7.1 % MFS Inflation-Adjusted Bond Fund 4.8 % MFS High Income Fund 4.0 % MFS Commodity Strategy Fund 4.0 % MFS Global Real Estate Fund 3.9 % MFS International Large Cap Value Fund 3.1 % MFS International Intrinsic Value Fund 3.0 % MFS International Growth Fund 3.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Global Opportunistic Bond Fund 3.0 % MFS Total Return Bond Fund 2.3 % MFS Institutional Money Market Portfolio 2.2 % MFS International New Discovery Fund 2.0 % MFS New Discovery Value Fund 2.0 % MFS Emerging Markets Equity Fund 2.0 % MFS New Discovery Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 1.9 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006852 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Moderate Allocation Fund
Class Name	Class R4
Trading Symbol	MAMJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Moderate Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 10	[160]
Expense Ratio, Percent	0.09%	[160]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Moderate Allocation Fund (fund) provided a total return of 13.77%, at net asset value. This compares with a return of 28.19% for the fund’s benchmark, the Standard & Poor's 500 Stock Index. The fund's other benchmark, the MFS Moderate Allocation Fund Blended Index (Blended Index), generated a return of 14.62%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to both the MFS High Income Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Global Opportunistic Bond Fund and MFS Total Return Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back the results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 13.77 % 7.14 % 6.25 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 28.19 % 15.80 % 12.69 % MFS Moderate Allocation Fund Blended Index ∆ 14.62 % 7.84 % 6.51 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 6,630,766,465
Holdings Count | Holding	23
Advisory Fees Paid, Amount	$ 0	[161]
Investment Company Portfolio Turnover	4%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,630,766,465 Total Management Fee ($)#: 0 Total Number of Holdings: 23 Portfolio Turnover (%): 4 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Government Securities Fund 9.2 % MFS Total Return Bond Fund 8.3 % MFS Value Fund 8.1 % MFS Growth Fund 7.3 % MFS Research Fund 7.3 % MFS Mid Cap Value Fund 7.1 % MFS Mid Cap Growth Fund 6.9 % MFS Inflation-Adjusted Bond Fund 6.8 % MFS Research International Fund 5.1 % MFS Global Opportunistic Bond Fund 4.9 % MFS High Income Fund 4.0 % MFS Emerging Markets Debt Fund 3.0 % MFS Commodity Strategy Fund 3.0 % MFS Global Real Estate Fund 3.0 % MFS Institutional Money Market Portfolio 2.9 % MFS International Large Cap Value Fund 2.1 % MFS International Intrinsic Value Fund 2.0 % MFS International Growth Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS New Discovery Value Fund 1.5 % MFS New Discovery Fund 1.5 % MFS International New Discovery Fund 1.0 % MFS Emerging Markets Equity Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006887 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class A
Trading Symbol	MACFX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ A $ 0.34 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 36	[162]
Expense Ratio, Percent	0.34%	[162]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Conservative Allocation Fund (fund) provided a total return of 10.05%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 10.05 % 5.03 ) % 4.57 % A with initial sales charge (5.75%) 3.73 % 3.80 ) % 3.95 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[163]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006888 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Conservative Allocation Fund
Class Name	Class R4
Trading Symbol	MACJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Conservative Allocation Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Material Fund Change Notice [Text Block]	This report describes changes to the Fund that occurred during the reporting period.
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.09 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 9	[164]
Expense Ratio, Percent	0.09%	[164]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS Conservative Allocation Fund (fund) provided a total return of 10.32%, at net asset value. This compares with a return of 1.31% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. The fund's other benchmark, the MFS Conservative Allocation Fund Blended Index (Blended Index), generated a return of 10.10%. The Blended Index reflects the blended returns of broad asset class indices, with percentage allocations to each index designed to resemble the long term strategic allocations of the fund. The market indices and related percentage allocations used to compile the Blended Index are set forth in the Performance Summary. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Blended Index Within the fixed income segment, the fund's exposure to the MFS High Income Fund, MFS Limited Maturity Fund and MFS Emerging Markets Debt Fund boosted relative returns. Additionally, strong relative performance of the MFS Total Return Bond Fund and MFS Global Opportunistic Bond Fund bolstered relative returns as both funds outperformed their respective benchmarks. Top detractors from performance relative to the Blended Index Within the US equity funds segment, style selection was a headwind. Diversified exposures into value and down in market cap lagged the US equity portion of the Blended Index. Within the international equity segment, relative performance of the MFS Research International Fund held back results as the fund lagged its respective benchmark.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 10.32 % 5.30 ) % 4.83 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.31 % (0.17 ) % 1.26 % MFS Conservative Allocation Fund Blended Index ∆ 10.10 % 5.25 ) % 4.90 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Material Change Date	Aug. 28, 2023
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 3,759,785,798
Holdings Count | Holding	22
Advisory Fees Paid, Amount	$ 0	[165]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 3,759,785,798 Total Management Fee ($)#: 0 Total Number of Holdings: 22 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio allocation Portfolio holdings MFS Total Return Bond Fund 14.4 % MFS Limited Maturity Fund 10.0 % MFS Inflation-Adjusted Bond Fund 9.9 % MFS Government Securities Fund 9.3 % MFS Global Opportunistic Bond Fund 7.0 % MFS Value Fund 6.0 % MFS Growth Fund 5.3 % MFS Research Fund 5.2 % MFS High Income Fund 4.0 % MFS Mid Cap Value Fund 4.0 % MFS Mid Cap Growth Fund 3.9 % MFS Research International Fund 3.5 % MFS Institutional Money Market Portfolio 3.0 % MFS Emerging Markets Debt Fund 2.0 % MFS Global Real Estate Fund 2.0 % MFS Emerging Markets Debt Local Currency Fund 2.0 % MFS Commodity Strategy Fund 2.0 % MFS International Large Cap Value Fund 1.5 % MFS International Intrinsic Value Fund 1.5 % MFS International Growth Fund 1.5 % MFS New Discovery Value Fund 1.0 % MFS New Discovery Fund 1.0 %
Material Fund Change [Text Block]	MATERIAL FUND CHANGES This is a summary of certain changes to the fund since June 1, 2023. For more complete information, you may review the fund's prospectus as amended, which is available at funds.mfs.com Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process. We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Material Fund Change Strategies [Text Block]	Effective August 28, 2023, we updated the fund’s principal investment strategies and principal risks in order to incorporate our proprietary analysis of projected performance of various asset classes, as well as other factors, into the fund’s strategic asset allocation process.
Material Fund Change Risks Change [Text Block]	We broadened the menu of available underlying MFS funds from which we may choose to invest the fund’s assets and added additional principal risks associated with this broader list of available underlying funds. We also updated the principal risk entitled “investment selection risk” to reflect this change and discuss the use of quantitative models.
Updated Prospectus Phone Number	1‑800‑225‑2606
Updated Prospectus Web Address	funds.mfs.com
C000006904 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Emerging Markets Equity Fund
Class Name	Class A
Trading Symbol	MEMAX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Emerging Markets Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 1.31 %
Expenses Paid, Amount	$ 138
Expense Ratio, Percent	1.31%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class A shares of the MFS Emerging Markets Equity Fund (fund) provided a total return of 10.99%, at net asset value. This compares with a return of 12.39% for the fund’s benchmark, the MSCI Emerging Markets Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI Emerging Markets Index Stock selection and underweight positions in both the health care and industrials sectors. Stock selection and, to a lesser extent, an overweight position in the energy sector. Top detractors from performance relative to the MSCI Emerging Markets Index Stock selection within the financials sector. An overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class A over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 10.99 % 1.46 % 1.51 % A with initial sales charge (5.75%) 4.60 % 0.26 % 0.91 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 12.39 % 3.55 % 2.66 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/a
Net Assets	$ 7,548,635,044
Holdings Count | Holding	97
Advisory Fees Paid, Amount	$ 63,850,201	[166]
Investment Company Portfolio Turnover	34%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 7,548,635,044 Total Management Fee ($)#: 63,850,201 Total Number of Holdings: 97 Portfolio Turnover (%): 34 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 97.9 % Money Market Funds 2.1 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 % Issuer country weightings China 26.4 % South Korea 14.8 % India 14.5 % Taiwan 14.1 % Brazil 6.9 % Indonesia 2.9 % Mexico 2.8 % Hong Kong 2.3 % United States 2.1 % Other Countries 13.2 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.5 % Samsung Electronics Co. Ltd. 5.8 % Tencent Holdings Ltd. 5.7 % Alibaba Group Holding Ltd. 3.0 % Infosys Ltd. 2.2 % China Construction Bank Corp. 1.8 % Tata Consultancy Services Ltd. 1.8 % Hon Hai Precision Industry Co. Ltd. 1.7 % Vale S.A., ADR 1.7 % HDFC Bank Ltd. 1.7 %
C000006925 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class R4
Trading Symbol	MDITX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R4 $ 0.10 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 11	[167]
Expense Ratio, Percent	0.10%	[167]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS International Diversification Fund (fund) provided a total return of 14.43%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 14.43 % 7.36 % 5.72 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[168]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006935 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International DiversificationSM Fund
Class Name	Class R2
Trading Symbol	MDIKX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Diversification Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment ~ Costs paid as a percentage of a $10,000 investment ~ R2 $ 0.60 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses.
Expenses Paid, Amount	$ 64	[169]
Expense Ratio, Percent	0.60%	[169]
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS International Diversification Fund (fund) provided a total return of 13.88%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Index During the reporting period, the fund's exposure to the MFS International Intrinsic Value Fund contributed to relative performance as the fund outperformed its respective market segment. Top detractors from performance relative to the MSCI All Country World (ex-US) Index Relative performance of the MFS Research International Fund, MFS International Large Cap Value Fund, MFS International New Discovery Fund and MFS Emerging Markets Equity Fund weakened relative returns as all four funds underperformed their respective benchmarks. The fund's exposure to the MFS International Growth Fund further weighed on relative returns.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 13.88 % 6.84 % 5.20 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) ∆ 16.74 % 6.81 % 4.03 % ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 38,625,457,251
Holdings Count | Holding	7
Advisory Fees Paid, Amount	$ 0	[170]
Investment Company Portfolio Turnover	3%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 38,625,457,251 Total Management Fee ($)#: 0 Total Number of Holdings: 7 Portfolio Turnover (%): 3 ♯
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio target allocation Portfolio actual allocation Portfolio holdings MFS Research International Fund 27.7 % MFS Emerging Markets Equity Fund 17.1 % MFS International Large Cap Value Fund 15.1 % MFS International Intrinsic Value Fund 15.0 % MFS International Growth Fund 15.0 % MFS International New Discovery Fund 10.0 % MFS Institutional Money Market Portfolio 0.1 %
C000006940 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class I
Trading Symbol	MQGIX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.84 %
Expenses Paid, Amount	$ 89
Expense Ratio, Percent	0.84%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS International Growth Fund (fund) provided a total return of 12.36%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 12.36 % 8.49 % 6.71 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[171]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000071430 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class R4
Trading Symbol	MGRVX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R4 $ 0.85 %
Expenses Paid, Amount	$ 90
Expense Ratio, Percent	0.85%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R4 shares of the MFS International Growth Fund (fund) provided a total return of 12.37%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R4 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 12.37 % 8.48 % 6.71 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r4
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[172]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000071432 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Growth Fund
Class Name	Class R2
Trading Symbol	MGRQX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Growth Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 1.35 %
Expenses Paid, Amount	$ 143
Expense Ratio, Percent	1.35%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS International Growth Fund (fund) provided a total return of 11.81%, at net asset value. This compares with a return of 16.74% for the fund’s benchmark, the MSCI All Country World (ex-US) Index (net div). The fund's other benchmark, the MSCI All Country World (ex-US) Growth Index (net div), generated a return of 13.01%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection and, to a lesser extent, an overweight position in the industrials sector were primary contributors to relative performance. Stock selection within both the information technology and materials sectors benefited relative results. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index Stock selection within the health care, consumer discretionary and financials sectors. Stock selection and, to a lesser extent, an overweight position in the consumer staples sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 11.81 % * 7.94 % 6.18 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 16.74 % * 6.81 % 4.03 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 13.01 % * 6.65 % 4.79 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. * If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 11.78%.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 16,586,855,867
Holdings Count | Holding	86
Advisory Fees Paid, Amount	$ 102,678,636	[173]
Investment Company Portfolio Turnover	13%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 16,586,855,867 Total Management Fee ($)#: 102,678,636 Total Number of Holdings: 86 Portfolio Turnover (%): 13 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.6 % Money Market Funds 1.4 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 % Issuer country weightings France 17.0 % Germany 10.5 % Switzerland 10.2 % Japan 9.3 % United Kingdom 8.2 % Canada 6.5 % Netherlands 5.6 % Taiwan 5.6 % United States 4.0 % Other Countries 23.1 %
Largest Holdings [Text Block]	Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.7 % Schneider Electric SE 4.5 % SAP SE 4.5 % Nestle S.A. 3.9 % Hitachi Ltd. 3.7 % Heineken N.V. 3.1 % LVMH Moet Hennessy Louis Vuitton SE 3.1 % Roche Holding AG 3.0 % Linde PLC 2.6 % Amadeus IT Group S.A. 2.3 %
C000160021 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class B
Trading Symbol	BRWBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.49 %
Expenses Paid, Amount	$ 177
Expense Ratio, Percent	1.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 37.14%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* B without sales charge 37.14 % 16.97 % 13.81 % B with CDSC (declining over six years from 4% to 0%) × 33.14 % 16.75 % 13.81 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[174]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160023 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class I
Trading Symbol	BRWJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.49 %
Expenses Paid, Amount	$ 58
Expense Ratio, Percent	0.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 38.56%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* I without sales charge 38.56 % 18.16 % 14.96 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[175]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160025 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Growth Equity Fund
Class Name	Class R2
Trading Symbol	BRWSX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Growth Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 0.99 %
Expenses Paid, Amount	$ 118
Expense Ratio, Percent	0.99%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R2 shares of the MFS Blended Research Growth Equity Fund (fund) provided a total return of 37.82%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 1000® Growth Index, generated a return of 33.60%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 1000® Growth Index Stock selection and an overweight position in the utilities sector were primary contributors to relative performance. Stock selection in the consumer discretionary, financials and information technology sectors benefited relative results. Top detractors from performance relative to the Russell 1000® Growth Index Stock selection in materials weighed on relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R2 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R2 without sales charge 37.82 % 17.57 % 14.38 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 1000® Growth Index +∆ 33.60 % 19.37 % 17.08 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r2
Net Assets	$ 338,805,753
Holdings Count | Holding	78
Advisory Fees Paid, Amount	$ 1,092,150	[176]
Investment Company Portfolio Turnover	48%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 338,805,753 Total Management Fee ($)#: 1,092,150 Total Number of Holdings: 78 Portfolio Turnover (%): 48 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.4 % Money Market Funds 0.6 % GICS equity sectors Information Technology 44.0 % Communication Services 13.5 % Consumer Discretionary 13.4 % Health Care 10.3 % Financials 6.4 % Industrials 4.5 % Consumer Staples 3.1 % Real Estate 1.8 % Utilities 1.1 % Energy 0.9 % Materials 0.4 % Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings NVIDIA Corp. 11.1 % Microsoft Corp. 10.3 % Apple, Inc. 9.5 % Amazon.com, Inc. 6.9 % Meta Platforms, Inc., "A" 4.8 % Alphabet, Inc., "C" 3.6 % Alphabet, Inc., "A" 3.6 % Applied Materials, Inc. 1.8 % Eli Lilly & Co. 1.7 % Booking Holdings, Inc. 1.7 %
C000160030 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class B
Trading Symbol	BRSBX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment B $ 1.74 %
Expenses Paid, Amount	$ 192
Expense Ratio, Percent	1.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class B shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 20.48%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class B over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* B without sales charge 20.48 % 6.75 % 7.65 % B with CDSC (declining over six years from 4% to 0%) × 16.48 % 6.44 % 7.65 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/b
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[177]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000160032 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research® Small Cap Equity Fund
Class Name	Class I
Trading Symbol	BRSJX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Small Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment I $ 0.74 %
Expenses Paid, Amount	$ 82
Expense Ratio, Percent	0.74%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class I shares of the MFS Blended Research Small Cap Equity Fund (fund) provided a total return of 21.68%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell 2000® Index, generated a return of 20.12%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell 2000® Index Stock selection within the industrials, financials, consumer staples and real estate sectors was a primary contributor to performance relative to the Russell 2000® Index. Top detractors from performance relative to the Russell 2000® Index Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. A combination of stock selection and an overweight position in the health care sector further weakened relative results.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class I over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* I without sales charge 21.68 % 7.81 % 8.73 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.44 % Russell 2000® Index +∆ 20.12 % 8.61 % 8.42 % * For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/i
Net Assets	$ 339,710,823
Holdings Count | Holding	179
Advisory Fees Paid, Amount	$ 1,997,025	[178]
Investment Company Portfolio Turnover	61%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 339,710,823 Total Management Fee ($)#: 1,997,025 Total Number of Holdings: 179 Portfolio Turnover (%): 61 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 99.3 % Money Market Funds 0.7 % GICS equity sectors Industrials 16.3 % Financials 16.2 % Health Care 16.2 % Information Technology 14.0 % Consumer Discretionary 10.8 % Real Estate 7.0 % Energy 7.0 % Materials 5.2 % Communication Services 2.9 % Consumer Staples 2.3 % Utilities 1.4 % Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Skechers USA, Inc., "A" 1.9 % Grand Canyon Education, Inc. 1.7 % e.l.f. Beauty, Inc. 1.6 % Encompass Health Corp. 1.5 % Organon & Co. 1.5 % APi Group, Inc. 1.5 % TaskUs, Inc., "A" 1.5 % Prestige Consumer Healthcare, Inc. 1.4 % Verint Systems, Inc. 1.4 % SLM Corp. 1.4 %
C000172723 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® Blended Research®Mid Cap Equity Fund
Class Name	Class R6
Trading Symbol	BMSYX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS Blended Research Mid Cap Equity Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R6 $ 0.49 %
Expenses Paid, Amount	$ 57
Expense Ratio, Percent	0.49%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class R6 shares of the MFS Blended Research Mid Cap Equity Fund (fund) provided a total return of 32.03%, at net asset value. This compares with a return of 27.58% for the fund’s benchmark, the Russell 3000® Index. The fund's other benchmark, the Russell Midcap® Index, generated a return of 23.11%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the Russell Midcap® Index Stock selection within the utilities, information technology, financials and communication services sectors was a primary contributor to relative performance. Top detractors from performance relative to the Russell Midcap® Index Security selection within the consumer discretionary sector dampened relative performance. The fund's cash and/or cash equivalents position during the period was also a detractor from relative performance. Under normal market conditions, the fund strives to be fully invested and generally holds cash to buy new holdings and to provide liquidity. In a period when equity markets rose, as measured by the fund's benchmark, holding cash hurt performance versus the benchmark, which has no cash position.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class R6 over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr 5-yr Life* R6 without sales charge 32.03 % 13.01 % 11.40 % Comparative Benchmark(s) Russell 3000® Index +∆ 27.58 % 15.00 % 13.37 % Russell Midcap® Index +∆ 23.11 % 11.07 % 10.18 % * For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024. + Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/r6
Net Assets	$ 699,333,781
Holdings Count | Holding	145
Advisory Fees Paid, Amount	$ 2,794,485	[179]
Investment Company Portfolio Turnover	75%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 699,333,781 Total Management Fee ($)#: 2,794,485 Total Number of Holdings: 145 Portfolio Turnover (%): 75 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 98.7 % Money Market Funds 1.3 % GICS equity sectors Industrials 18.5 % Financials 17.3 % Information Technology 12.0 % Health Care 10.5 % Consumer Discretionary 9.4 % Real Estate 7.9 % Utilities 6.8 % Energy 5.2 % Materials 5.0 % Communication Services 4.1 % Consumer Staples 2.0 % Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 % MFS uses the Global Industry Classification Standard (GICS ®
Largest Holdings [Text Block]	Top ten holdings Ameriprise Financial, Inc. 2.0 % Phillips 66 2.0 % Spotify Technology S.A. 1.9 % Hartford Financial Services Group, Inc. 1.8 % Wabtec Corp. 1.5 % Corebridge Financial, Inc. 1.5 % Equitable Holdings, Inc. 1.5 % McKesson Corp. 1.5 % Verisk Analytics, Inc., "A" 1.5 % Vistra Corp. 1.5 %
C000220112 [Member]
Shareholder Report [Line Items]
Fund Name	MFS® International Large Cap Value Fund
Class Name	Class C
Trading Symbol	MKVCX
Annual or Semi-Annual Statement [Text Block]	This annual shareholder report contains important information about MFS International Large Cap Value Fund for the period of June 1, 2023 to May 31, 2024.
Shareholder Report Annual or Semi-Annual	annual shareholder report
Additional Information [Text Block]	You can find additional information about the fund at funds.mfs.com
Additional Information Phone Number	1‑800‑225‑2606
Additional Information Email	orderliterature@mfs.com
Additional Information Website	funds.mfs.com
Expenses [Text Block]	FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment C $ 1.72 %
Expenses Paid, Amount	$ 187
Expense Ratio, Percent	1.72%
Factors Affecting Performance [Text Block]	MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended May 31, 2024, Class C shares of the MFS International Large Cap Value Fund (fund) provided a total return of 17.02%, at net asset value. This compares with a return of 18.53% for the fund’s benchmark, the MSCI EAFE (Europe, Australasia, Far East) Index (net div). The fund's other benchmark, the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div), generated a return of 23.58%. In response to the strongest inflationary period in four decades, global central banks tightened monetary policy significantly during the reporting period, helping reduce price pressures, although progress toward inflation targets remains uneven. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. The US sought to restrict the flow of advanced technologies to China and China looked to use its industrial overcapacity to increase exports to developed markets to bolster its slow-growing domestic economy. Global equity markets reached record levels at the end of the period as they weathered the unsettled geopolitical climate and higher interest rate environment well. Top contributors to performance relative to the MSCI EAFE Value Index Not owning any stocks within the real estate sector. Stock selection within the energy sector. Top detractors from performance relative to the MSCI EAFE Value Index Stock selection within the financials sector. Stock selection and an overweight position in the consumer staples sector; stock selection within the consumer discretionary sector.
Performance Past Does Not Indicate Future [Text]	The fund’s past performance is not a good predictor of the fund’s future performance.
Line Graph [Table Text Block]	FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment* This graph shows the performance of a hypothetical $10,000 investment in Class C over a ten year period or since inception, if shorter, in comparison to (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests. This graph includes the deduction of the maximum applicable sales charge, if any.
Average Annual Return [Table Text Block]	Average Annual Total Returns through 5/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of (i) a broad measure of market performance and (ii) an additional index that MFS believes more closely reflects the market segments in which the fund invests, over the same periods. Share Class 1-yr Life* C without sales charge 17.02 % 11.18 % C with CDSC (1% for 12 months) × 16.02 % 11.18 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) +∆ 18.53 % 10.31 % MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) +∆ 23.58 % 13.06 % * For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024. + Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. CDSC – Contingent Deferred Sales Charge.
No Deduction of Taxes [Text Block]	The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.
Performance Table Market Index Changed [Text Block]	Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.
Updated Performance Information Location [Text Block]	Visit mfs.com/perf/c
Net Assets	$ 6,436,302,634
Holdings Count | Holding	96
Advisory Fees Paid, Amount	$ 42,838,077	[180]
Investment Company Portfolio Turnover	17%
Additional Fund Statistics [Text Block]	FUND STATISTICS AS OF 5/31/24 Net Assets ($): 6,436,302,634 Total Management Fee ($)#: 42,838,077 Total Number of Holdings: 96 Portfolio Turnover (%): 17 ♯ Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
Holdings [Text Block]	PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 5/31/24) Portfolio structure Equities 96.8 % Money Market Funds 3.2 % Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 % Issuer country weightings United Kingdom 23.9 % Japan 16.2 % France 15.1 % Switzerland 9.0 % United States 6.2 % Canada 5.8 % Germany 5.6 % Ireland 3.9 % Netherlands 2.8 % Other Countries 11.5 %
Largest Holdings [Text Block]	Top ten holdings Mitsubishi UFJ Financial Group, Inc. 3.5 % BNP Paribas S.A. 3.3 % UBS Group AG 3.2 % NatWest Group PLC 3.1 % Eni S.p.A. 2.7 % Schneider Electric SE 2.5 % Roche Holding AG 2.4 % Glencore PLC 2.2 % Willis Towers Watson PLC 2.1 % Henkel AG & Co. KGaA 2.0 %
[1]Expenses are direct expenses and do not include underlying fund fees and expenses.[2]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[3]Expenses are direct expenses and do not include underlying fund fees and expenses.[4]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[5]Expenses are direct expenses and do not include underlying fund fees and expenses.[6]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[7]Includes the effect of any management fee waivers.[8]Includes the effect of any management fee waivers.[9]Expenses are direct expenses and do not include underlying fund fees and expenses.[10]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[11]Expenses are direct expenses and do not include underlying fund fees and expenses.[12]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[13]Includes the effect of any management fee waivers.[14]Includes the effect of any management fee waivers.[15]Expenses are direct expenses and do not include underlying fund fees and expenses.[16]Includes the effect of any management fee waivers.[17]Includes the effect of any management fee waivers.[18]Includes the effect of any management fee waivers.[19]Includes the effect of any management fee waivers.[20]Includes the effect of any management fee waivers.[21]Includes the effect of any management fee waivers.[22]Expenses are direct expenses and do not include underlying fund fees and expenses.[23]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[24]Expenses are direct expenses and do not include underlying fund fees and expenses.[25]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[26]Expenses are direct expenses and do not include underlying fund fees and expenses.[27]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[28]Expenses are direct expenses and do not include underlying fund fees and expenses.[29]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[30]Expenses are direct expenses and do not include underlying fund fees and expenses.[31]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[32]Expenses are direct expenses and do not include underlying fund fees and expenses.[33]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[34]Includes the effect of any management fee waivers.[35]Includes the effect of any management fee waivers.[36]Includes the effect of any management fee waivers.[37]Includes the effect of any management fee waivers.[38]Includes the effect of any management fee waivers.[39]Includes the effect of any management fee waivers.[40]Includes the effect of any management fee waivers.[41]Includes the effect of any management fee waivers.[42]Expenses are direct expenses and do not include underlying fund fees and expenses.[43]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[44]Includes the effect of any management fee waivers.[45]Includes the effect of any management fee waivers.[46]Expenses are direct expenses and do not include underlying fund fees and expenses.[47]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[48]Expenses are direct expenses and do not include underlying fund fees and expenses.[49]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[50]Expenses are direct expenses and do not include underlying fund fees and expenses.[51]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[52]Expenses are direct expenses and do not include underlying fund fees and expenses.[53]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[54]Includes the effect of any management fee waivers.[55]Includes the effect of any management fee waivers.[56]Includes the effect of any management fee waivers.[57]Expenses are direct expenses and do not include underlying fund fees and expenses.[58]Includes the effect of any management fee waivers.[59]Includes the effect of any management fee waivers.[60]Includes the effect of any management fee waivers.[61]Includes the effect of any management fee waivers.[62]Includes the effect of any management fee waivers.[63]Includes the effect of any management fee waivers.[64]Includes the effect of any management fee waivers.[65]Expenses are direct expenses and do not include underlying fund fees and expenses.[66]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[67]Expenses are direct expenses and do not include underlying fund fees and expenses.[68]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[69]Expenses are direct expenses and do not include underlying fund fees and expenses.[70]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[71]Expenses are direct expenses and do not include underlying fund fees and expenses.[72]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[73]Expenses are direct expenses and do not include underlying fund fees and expenses.[74]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[75]Expenses are direct expenses and do not include underlying fund fees and expenses.[76]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[77]Expenses are direct expenses and do not include underlying fund fees and expenses.[78]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[79]Includes the effect of any management fee waivers.[80]Includes the effect of any management fee waivers.[81]Includes the effect of any management fee waivers.[82]Includes the effect of any management fee waivers.[83]Expenses are direct expenses and do not include underlying fund fees and expenses.[84]Includes the effect of any management fee waivers.[85]Expenses are direct expenses and do not include underlying fund fees and expenses.[86]Includes the effect of any management fee waivers.[87]Includes the effect of any management fee waivers.[88]Includes the effect of any management fee waivers.[89]Includes the effect of any management fee waivers.[90]Includes the effect of any management fee waivers.[91]Expenses are direct expenses and do not include underlying fund fees and expenses.[92]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[93]Expenses are direct expenses and do not include underlying fund fees and expenses.[94]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[95]Includes the effect of any management fee waivers.[96]Expenses are direct expenses and do not include underlying fund fees and expenses.[97]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[98]Expenses are direct expenses and do not include underlying fund fees and expenses.[99]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[100]Includes the effect of any management fee waivers.[101]Includes the effect of any management fee waivers.[102]Includes the effect of any management fee waivers.[103]Expenses are direct expenses and do not include underlying fund fees and expenses.[104]Includes the effect of any management fee waivers.[105]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[106]Includes the effect of any management fee waivers.[107]Includes the effect of any management fee waivers.[108]Includes the effect of any management fee waivers.[109]Includes the effect of any management fee waivers.[110]Expenses are direct expenses and do not include underlying fund fees and expenses.[111]Includes the effect of any management fee waivers.[112]Expenses are direct expenses and do not include underlying fund fees and expenses.[113]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[114]Expenses are direct expenses and do not include underlying fund fees and expenses.[115]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[116]Expenses are direct expenses and do not include underlying fund fees and expenses.[117]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[118]Expenses are direct expenses and do not include underlying fund fees and expenses.[119]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[120]Expenses are direct expenses and do not include underlying fund fees and expenses.[121]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[122]Expenses are direct expenses and do not include underlying fund fees and expenses.[123]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[124]Expenses are direct expenses and do not include underlying fund fees and expenses.[125]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[126]Includes the effect of any management fee waivers.[127]Includes the effect of any management fee waivers.[128]Expenses are direct expenses and do not include underlying fund fees and expenses.[129]Includes the effect of any management fee waivers.[130]Expenses are direct expenses and do not include underlying fund fees and expenses.[131]Includes the effect of any management fee waivers.[132]Includes the effect of any management fee waivers.[133]Includes the effect of any management fee waivers.[134]Includes the effect of any management fee waivers.[135]Includes the effect of any management fee waivers.[136]Includes the effect of any management fee waivers.[137]Includes the effect of any management fee waivers.[138]Expenses are direct expenses and do not include underlying fund fees and expenses.[139]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[140]Expenses are direct expenses and do not include underlying fund fees and expenses.[141]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[142]Expenses are direct expenses and do not include underlying fund fees and expenses.[143]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[144]Includes the effect of any management fee waivers.[145]Includes the effect of any management fee waivers.[146]Includes the effect of any management fee waivers.[147]Expenses are direct expenses and do not include underlying fund fees and expenses.[148]Includes the effect of any management fee waivers.[149]Includes the effect of any management fee waivers.[150]Includes the effect of any management fee waivers.[151]Includes the effect of any management fee waivers.[152]Includes the effect of any management fee waivers.[153]Includes the effect of any management fee waivers.[154]Expenses are direct expenses and do not include underlying fund fees and expenses.[155]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[156]Expenses are direct expenses and do not include underlying fund fees and expenses.[157]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[158]Expenses are direct expenses and do not include underlying fund fees and expenses.[159]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[160]Expenses are direct expenses and do not include underlying fund fees and expenses.[161]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[162]Expenses are direct expenses and do not include underlying fund fees and expenses.[163]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[164]Expenses are direct expenses and do not include underlying fund fees and expenses.[165]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[166]Includes the effect of any management fee waivers.[167]Expenses are direct expenses and do not include underlying fund fees and expenses.[168]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[169]Expenses are direct expenses and do not include underlying fund fees and expenses.[170]The fund itself does not pay a management fee but the underlying funds in which the fund invests do pay management fees to MFS.[171]Includes the effect of any management fee waivers.[172]Includes the effect of any management fee waivers.[173]Includes the effect of any management fee waivers.[174]Includes the effect of any management fee waivers.[175]Includes the effect of any management fee waivers.[176]Includes the effect of any management fee waivers.[177]Includes the effect of any management fee waivers.[178]Includes the effect of any management fee waivers.[179]Includes the effect of any management fee waivers.[180]Includes the effect of any management fee waivers.

Shareholder Report, Line Graph

Shareholder Report, Line Graph (Details) - USD ($)		12 Months Ended		32 Months Ended		47 Months Ended		60 Months Ended			80 Months Ended		93 Months Ended		105 Months Ended		119 Months Ended		120 Months Ended
		May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024	May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024		May 31, 2024	May 31, 2023	May 31, 2022	Sep. 30, 2021	May 31, 2021	Jun. 30, 2020	May 31, 2020	May 31, 2019	May 31, 2018	Oct. 02, 2017	May 31, 2017	Aug. 19, 2016	May 31, 2016	Sep. 15, 2015	May 31, 2015	Jun. 27, 2014	May 31, 2014
C000006857 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 16,593		$ 16,593		$ 16,593		$ 16,593		$ 16,593	$ 16,593		$ 16,593		$ 16,593		$ 16,593		$ 16,593		$ 16,593		$ 16,593	$ 14,731	$ 15,135		$ 16,222		$ 13,162	$ 12,353	$ 11,931		$ 11,178		$ 10,215		$ 10,327		$ 10,000
Average Annual Return, Percent	[1]	11.64%						6.08%													5.19%
C000006857 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		12.64%						6.08%													5.19%
C000006860 [Member]
Account Value [Line Items]
Account Value		$ 16,591		16,591		16,591		$ 16,591		16,591	16,591		16,591		16,591		16,591		16,591		$ 16,591		16,591	14,729	15,137		16,222		13,155	12,354	11,933		11,183		10,212		10,326		10,000
C000006860 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		12.65%						6.07%													5.19%
C000006863 [Member]
Account Value [Line Items]
Account Value		$ 17,882		17,882		17,882		$ 17,882		17,882	17,882		17,882		17,882		17,882		17,882		$ 17,882		17,882	15,756	16,071		17,099		13,760	12,818	12,299		11,434		10,365		10,404		10,000
C000006863 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		13.49%						6.89%													5.98%
C000006905 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 10,774		10,774		10,774		$ 10,774		10,774	10,774		10,774		10,774		10,774		10,774		$ 10,774		10,774	9,782	10,240		13,663		9,343	10,409	11,550		10,104		8,008		9,340		10,000
Average Annual Return, Percent	[2]	6.14%						0.30%													0.75%
C000006905 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		10.14%						0.69%													0.75%
C000006907 [Member]
Account Value [Line Items]
Account Value		$ 11,910		11,910		11,910		$ 11,910		11,910	11,910		11,910		11,910		11,910		11,910		$ 11,910		11,910	10,704	11,096		14,655		9,922	10,942	12,022		10,411		8,169		9,434		10,000
C000006907 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		11.27%						1.71%													1.76%
C000006924 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 16,033		16,033		16,033		$ 16,033		16,033	16,033		16,033		16,033		16,033		16,033		$ 16,033		16,033	14,041	13,819		16,136		11,694	11,376	11,626		10,525		8,906		9,511		9,425
Average Annual Return, Percent		7.62%						5.84%													4.83%
C000006924 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		14.19%						7.10%													5.46%
C000006930 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 15,791		15,791		15,791		$ 15,791		15,791	15,791		15,791		15,791		15,791		15,791		$ 15,791		15,791	13,937	13,821		16,250		11,871	11,633	11,977		10,921		9,312		10,021		10,000
Average Annual Return, Percent	[3]	12.30%						6.30%													4.67%
C000006930 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		13.30%						6.30%													4.67%
C000006942 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 18,806		18,806		18,806		$ 18,806		18,806	18,806		18,806		18,806		18,806		18,806		$ 18,806		18,806	15,912	15,462		18,405		14,478	13,284	13,084		12,252		10,557		10,468		10,000
Average Annual Return, Percent	[4]	14.19%						6.91%													6.52%
C000006942 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		18.19%	[5]					7.20%													6.52%
C000034484 [Member]
Account Value [Line Items]
Account Value		$ 19,350		19,350		19,350		$ 19,350		19,350	19,350		19,350		19,350		19,350		19,350		$ 19,350		19,350	17,200	16,145		18,393		13,393	12,804	12,844		11,375		9,552		10,060		10,000
C000034484 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		12.50%						8.61%													6.82%
C000142782 [Member]
Account Value [Line Items]
Account Value		$ 13,518		13,518		13,518		$ 13,518		13,518	13,518		13,518		13,518		$ 13,518		13,518		$ 13,518		13,518	12,401	12,097		12,315		12,343	11,597	10,978		10,642		10,195		10,247	$ 10,000
C000142782 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		9.01%						3.11%									3.08%	[6]
C000160020 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 31,032		31,032		31,032		$ 31,032		31,032	31,032		31,032		$ 31,032		$ 31,032		31,032		31,032		31,032	22,459	21,483		23,080		16,984	13,659	13,530		11,439		9,690	$ 9,425
Average Annual Return, Percent		30.23%						16.45%							13.88%	[7]
C000160020 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		38.18%						17.84%							14.66%	[7]
C000160035 [Member]
Account Value [Line Items]
Account Value		$ 20,293		20,293		20,293		$ 20,293		20,293	20,293		20,293		$ 20,293		20,293		20,293		20,293		20,293	16,709	18,301		19,796		12,704	14,103	14,435		12,000		10,386	10,000
C000160035 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		21.45%						7.55%							8.46%	[8]
C000160037 [Member]
Account Value [Line Items]
Account Value		$ 20,891		20,891		20,891		$ 20,891		20,891	20,891		20,891		$ 20,891		20,891		20,891		20,891		20,891	17,147	18,711		20,169		12,896	14,264	14,555		12,058		10,404	10,000
C000160037 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		21.83%						7.93%							8.83%	[9]
C000172720 [Member]
Account Value [Line Items]
Account Value		$ 22,137		22,137		22,137		$ 22,137		22,137	22,137		$ 22,137		$ 22,137		22,137		22,137		22,137		22,137	16,867	17,666		17,894		12,405	12,379	12,468		11,051	$ 10,000
C000172720 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		31.24%						12.33%					10.75%	[10]
C000172722 [Member]
Account Value [Line Items]
Account Value		$ 23,026		23,026		23,026		$ 23,026		23,026	23,026		$ 23,026		23,026		23,026		23,026		23,026		23,026	17,452	18,194		18,325		12,643	12,551	12,589		11,091	10,000
C000172722 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		31.93%						12.90%					11.31%	[11]
C000006845 [Member]
Account Value [Line Items]
Account Value		$ 23,229		23,229		23,229		$ 23,229		23,229	23,229		$ 23,229		23,229		23,229		23,229		$ 23,229		23,229	19,306	19,647		20,816		15,003	14,116	13,697		12,110		10,486		10,616		10,000
C000006845 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		20.32%						10.47%													8.79%
C000006850 [Member]
Account Value [Line Items]
Account Value		$ 22,660		22,660		22,660		$ 22,660		22,660	22,660		22,660		22,660		22,660		22,660		$ 22,660		22,660	18,887	19,267		20,457		14,784	13,946	13,569		12,027		10,433		10,589		10,000
C000006850 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		19.98%						10.19%													8.52%
C000006893 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 14,501		14,501		14,501		$ 14,501		$ 14,501	14,501		14,501		14,501		14,501		14,501		$ 14,501		$ 14,501	13,275	13,589		14,542		12,513	11,778	11,338		10,897		10,190		10,239		10,000
Average Annual Return, Percent	[12]	8.24%								4.25%													3.79%
C000006893 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		9.24%								4.25%													3.79%
C000006894 [Member]
Account Value [Line Items]
Account Value		$ 16,029		16,029		16,029		16,029		$ 16,029	16,029		16,029		16,029		16,029		16,029		16,029		$ 16,029	14,527	14,724		15,602		13,291	12,383	11,806		11,230		10,399		10,339		10,000
C000006894 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		10.34%								5.30%													4.83%
C000006917 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 18,949		18,949		18,949		$ 18,949		$ 18,949	18,949		18,949		18,949		18,949		18,949		$ 18,949		$ 18,949	16,273	16,719		17,867		13,636	12,918	12,562		11,479		10,209		10,402		10,000
Average Annual Return, Percent	[13]	15.45%						7.96%													6.60%
C000006917 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		16.45%						7.96%													6.60%
C000006918 [Member]
Account Value [Line Items]
Account Value		$ 20,933		20,933		20,933		$ 20,933		20,933	20,933		20,933		20,933		20,933		20,933		$ 20,933		20,933	17,800	18,106		19,162		14,480	13,572	13,070		11,828		10,411		10,509		10,000
C000006918 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		17.60%						9.05%													7.67%
C000006939 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 17,322		17,322		17,322		$ 17,322		17,322	17,322		17,322		17,322		17,322		17,322		$ 17,322		17,322	15,571	14,783		17,030		12,539	12,119	12,288		11,004		9,340		9,950		10,000
Average Annual Return, Percent	[14]	10.24%						7.40%													5.65%
C000006939 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		11.24%						7.40%													5.65%
C000034485 [Member]
Account Value [Line Items]
Account Value		$ 21,001		21,001		21,001		$ 21,001		21,001	21,001		21,001		21,001		21,001		21,001		$ 21,001		21,001	17,572	16,885		19,879		15,467	14,034	13,673		12,664		10,790		10,582		10,000
C000034485 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		19.51%	[15]					8.40%													7.70%
C000071437 [Member]
Account Value [Line Items]
Account Value		$ 20,785		20,785		20,785		$ 20,785		20,785	20,785		20,785		20,785		20,785		20,785		$ 20,785		20,785	17,407	16,746		19,738		15,373	13,964	13,619		12,624		10,769		10,571		10,000
C000071437 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		19.41%	[16]					8.28%													7.59%
C000160027 [Member]
Account Value [Line Items]
Account Value		$ 33,686		33,686		33,686		$ 33,686		33,686	33,686		33,686		$ 33,686		33,686		33,686		$ 33,686		33,686	24,321	23,207		24,858		18,232	14,632	14,461		12,188		10,297	10,000
C000160027 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		38.51%						18.15%							14.96%	[17]
C000160028 [Member]
Account Value [Line Items]
Account Value		$ 33,903		33,903		33,903		$ 33,903		33,903	33,903		33,903		$ 33,903		33,903		33,903		33,903		33,903	24,456	23,313		24,951		18,296	14,663	14,485		12,202		10,297	10,000
C000160028 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		38.63%						18.25%							15.05%	[18]
C000160042 [Member]
Account Value [Line Items]
Account Value		$ 22,458		22,458		22,458		$ 22,458		22,458	22,458		22,458		$ 22,458		22,458		22,458		22,458		22,458	17,683	18,323		17,782		12,429	12,918	13,229		11,878		10,620	10,000
C000160042 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		27%						11.70%							9.73%	[19]
C000160045 [Member]
Account Value [Line Items]
Account Value		$ 23,949		23,949		23,949		$ 23,949		23,949	23,949		23,949		$ 23,949		23,949		23,949		23,949		23,949	18,813	19,454		18,819		13,021	13,405	13,586		12,078		10,692	10,000
C000160045 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		27.30%						12.31%							10.55%	[20]
C000160046 [Member]
Account Value [Line Items]
Account Value		$ 24,116		24,116		24,116		$ 24,116		24,116	24,116		24,116		$ 24,116		24,116		24,116		24,116		24,116	18,939	19,555		18,911		13,080	13,442	13,609		12,091		10,692	10,000
C000160046 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		27.34%						12.40%							10.63%	[21]
C000195683 [Member]
Account Value [Line Items]
Account Value		$ 14,919		14,919		14,919		$ 14,919		14,919	$ 14,919		14,919		$ 14,919		14,919		14,919		14,919		14,919	13,021	12,775		14,861		10,735	10,405	10,598	$ 10,000
C000195683 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		14.58%						7.47%			6.18%	[22]
C000220110 [Member]
Account Value [Line Items]
Account Value		$ 15,150		15,150		$ 15,150		$ 15,150		15,150	$ 15,150		15,150		15,150		15,150		15,150		15,150		15,150	12,951	12,728		13,671	$ 10,000
C000220110 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		16.98%				11.18%	[23]
C000220113 [Member]
Account Value [Line Items]
Account Value		$ 15,437		15,437		$ 15,437		15,437		15,437	15,437		15,437		15,437		15,437		15,437		15,437		15,437	13,132	12,842		13,723	10,000
C000220113 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		17.56%				11.71%	[24]
C000006856 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 16,597		16,597		$ 16,597		$ 16,597		16,597	16,597		16,597		16,597		16,597		16,597		$ 16,597		16,597	14,731	15,139		16,228		13,161	12,350	11,934		11,180		10,216		10,329		10,000
Average Annual Return, Percent	[25]	8.67%						5.77%													5.20%
C000006856 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		12.67%						6.09%													5.20%
C000006899 [Member]
Account Value [Line Items]
Account Value		$ 15,624		15,624		15,624		$ 15,624		15,624	15,624		15,624		15,624		15,624		15,624		$ 15,624		15,624	14,202	14,428		15,326		13,094	12,222	11,687		11,143		10,347		10,312		10,000
C000006899 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		10.01%						5.03%													4.56%
C000006923 [Member]
Account Value [Line Items]
Account Value		$ 20,425		20,425		20,425		$ 20,425		20,425	20,425		20,425		20,425		20,425		20,425		$ 20,425		20,425	17,408	17,759		18,834		14,264	13,413	12,948		11,744		10,364		10,485		10,000
C000006923 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		17.33%						8.78%													7.40%
C000006933 [Member]
Account Value [Line Items]
Account Value		$ 15,777		15,777		15,777		$ 15,777		15,777	15,777		15,777		15,777		15,777		15,777		$ 15,777		15,777	13,932	13,813		16,248		11,865	11,628	11,977		10,918		9,308		10,018		10,000
C000006933 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		13.25%						6.29%													4.67%
C000071428 [Member]
Account Value [Line Items]
Account Value		$ 12,056		12,056		12,056		$ 12,056		12,056	12,056		12,056		12,056		12,056		12,056		$ 12,056		12,056	10,818	11,195		14,768		9,986	11,002	12,072		10,443		8,189		9,440		10,000
C000071428 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		11.45%						1.85%													1.89%
C000071433 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Account Value		$ 18,671		18,671		18,671		$ 18,671		18,671	18,671		18,671		18,671		18,671		18,671		$ 18,671		18,671	16,658	15,698		17,948		13,113	12,582	12,662		11,253		9,482		10,027		10,000
C000071433 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Average Annual Return, Percent		12.09%						8.21%													6.44%
C000071434 [Member]
Account Value [Line Items]
Account Value		$ 18,805		18,805		18,805		$ 18,805		18,805	18,805		18,805		18,805		18,805		18,805		$ 18,805		18,805	15,907	15,459		18,403		14,477	13,281	13,082		12,250		10,553		10,465		10,000
C000071434 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		18.22%						7.20%													6.52%
C000142777 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 12,248		12,248		12,248		$ 12,248		12,248	12,248		12,248		12,248		$ 12,248		12,248		$ 12,248		12,248	11,342	11,186		11,498		11,634	11,052	10,562		10,334		10,021		10,153	10,000
Average Annual Return, Percent	[26]	6.99%						2.08%									2.06%	[27]
C000142777 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		7.99%						2.08%									2.06%	[27]
C000160024 [Member]
Account Value [Line Items]
Account Value		$ 30,858		30,858		30,858		$ 30,858		30,858	30,858		30,858		$ 30,858		$ 30,858		30,858		30,858		30,858	22,498	21,680		23,459		17,389	14,098	14,073		11,987		10,226	10,000
C000160024 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		37.16%						16.96%							13.81%	[28]
C000160031 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 19,022		19,022		19,022		$ 19,022		19,022	19,022		19,022		$ 19,022		19,022		19,022		19,022		19,022	15,773	17,400		18,969		12,274	13,718	14,148		11,851		10,338	10,000
Average Annual Return, Percent	[29]	19.60%						6.76%							7.66%	[30]
C000160031 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		20.60%						6.76%							7.66%	[30]
C000160038 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 22,079		22,079		22,079		$ 22,079		22,079	22,079		22,079		$ 22,079		22,079		22,079		22,079		22,079	17,381	18,014		17,486		12,129	12,509	12,715		11,334		10,056	9,425
Average Annual Return, Percent		19.72%						10.72%							9.52%	[31]
C000160038 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		27.03%						12.03%							10.27%	[31]
C000172717 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)×
Account Value		$ 21,298		21,298		21,298		$ 21,298		21,298	21,298		$ 21,298		$ 21,298		21,298		21,298		21,298		21,298	16,309	17,164		17,468		12,174	12,208	12,365		11,002	10,000
Average Annual Return, Percent	[32]	29.59%						11.77%					10.20%	[33]
C000172717 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		30.59%						11.77%					10.20%	[33]
C000220106 [Member]
Account Value [Line Items]
Account Value		$ 15,795		15,795		$ 15,795		$ 15,795		15,795	15,795		$ 15,795		15,795		15,795		15,795		15,795		15,795	13,359	13,000		13,809	10,000
C000220106 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		18.24%				12.37%	[34]
C000220109 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 14,720		14,720		$ 14,720		14,720		14,720	14,720		14,720		14,720		14,720		14,720		14,720		14,720	12,483	12,184		12,984	9,425
Average Annual Return, Percent		11.14%				10.37%	[35]
C000220109 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		17.92%				12.05%	[35]
C000231059 [Member]
Account Value [Line Items]
Account Value		$ 10,367		$ 10,367		$ 10,367		10,367		10,367	10,367		10,367		10,367		10,367		10,367		10,367		10,367	9,104	9,261	$ 10,000
C000231059 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		13.87%		1.36%	[36]
C000006838 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 21,361		$ 21,361		21,361		$ 21,361		21,361	21,361		21,361		21,361		21,361		21,361		$ 21,361		21,361	17,805	18,160		19,286		13,931	13,146	12,785		11,333		9,836		9,980		9,425
Average Annual Return, Percent		13.07%						8.90%													7.89%
C000006838 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		19.97%						10.20%													8.53%
C000006839 [Member]
Account Value [Line Items]
Account Value		$ 23,227		23,227		23,227		$ 23,227		23,227	23,227		23,227		23,227		23,227		23,227		$ 23,227		23,227	19,313	19,654		20,820		15,006	14,118	13,700		12,114		10,486		10,618		10,000
C000006839 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		20.26%						10.47%													8.79%
C000006844 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 21,019		21,019		21,019		$ 21,019		21,019	21,019		21,019		21,019		21,019		21,019		$ 21,019		21,019	17,647	18,138		19,412		14,129	13,431	13,162		11,755		10,273		10,508		10,000
Average Annual Return, Percent	[37]	18.11%						9.37%													7.71%
C000006844 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		19.11%						9.37%													7.71%
C000006851 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 16,853		16,853		16,853		$ 16,853		16,853	16,853		16,853		16,853		16,853		16,853		$ 16,853		16,853	14,852	15,153		16,120		12,976	12,088	11,594		10,780		9,773		9,804		9,425
Average Annual Return, Percent		6.95%						5.61%													5.36%
C000006851 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		13.48%						6.87%													5.98%
C000006912 [Member]
Account Value [Line Items]
Account Value		$ 20,942		20,942		20,942		$ 20,942		20,942	20,942		20,942		20,942		20,942		20,942		$ 20,942		20,942	17,810	18,111		19,165		14,480	13,575	13,075		11,833		10,414		10,507		10,000
C000006912 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		17.59%						9.06%													7.67%
C000006922 [Member]
Account Value [Line Items]
Account Value		$ 19,927		19,927		19,927		$ 19,927		19,927	19,927		19,927		19,927		19,927		19,927		$ 19,927		19,927	17,031	17,411		18,507		14,055	13,245	12,816		11,658		10,313		10,459		10,000
C000006922 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		17%						8.51%													7.14%
C000006944 [Member]
Account Value [Line Items]
Account Value		$ 20,787		20,787		20,787		$ 20,787		20,787	20,787		20,787		20,787		20,787		20,787		$ 20,787		20,787	17,409	16,750		19,739		15,374	13,965	13,620		12,625		10,768		10,570		10,000
C000006944 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		19.41%	[38]					8.28%													7.59%
C000071425 [Member]
Account Value [Line Items]
Account Value		$ 11,327		11,327		11,327		$ 11,327		11,327	11,327		11,327		11,327		11,327		11,327		$ 11,327		11,327	10,231	10,656		14,147		9,625	10,671	11,784		10,255		8,089		9,384		10,000
C000071425 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		10.71%						1.20%													1.25%
C000071427 [Member]
Account Value [Line Items]
Account Value		$ 11,907		11,907		11,907		$ 11,907		11,907	11,907		11,907		11,907		11,907		11,907		$ 11,907		11,907	10,701	11,092		14,652		9,923	10,941	12,023		10,412		8,172		9,432		10,000
C000071427 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		11.27%						1.71%													1.76%
C000071435 [Member]
Account Value [Line Items]
Account Value		$ 19,771		19,771		19,771		$ 19,771		19,771	19,771		19,771		19,771		19,771		19,771		$ 19,771		19,771	16,644	16,094		19,061		14,918	13,617	13,348		12,435		10,663		10,519		10,000
C000071435 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		18.79%	[39]					7.74%													7.05%
C000142778 [Member]
Account Value [Line Items]
Account Value		$ 13,514		13,514		13,514		$ 13,514		13,514	13,514		13,514		13,514		$ 13,514		13,514		$ 13,514		13,514	12,397	12,097		12,315		12,340	11,604	10,975		10,642		10,205		10,247	10,000
C000142778 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		9.01%						3.09%									3.08%	[40]
C000142780 [Member]
Account Value [Line Items]
Account Value		$ 12,874		12,874		12,874		$ 12,874		$ 12,874	12,874		12,874		12,874		$ 12,874		$ 12,874		12,874		12,874	11,862	11,636		11,908		11,981	11,325	10,773		10,493		10,111		10,201	10,000
C000142780 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		8.53%								2.60%									2.58%	[41]
C000160039 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 21,945		21,945		21,945		$ 21,945		$ 21,945	21,945		21,945		$ 21,945		21,945		$ 21,945		21,945		21,945	17,410	18,190		17,778		12,423	12,923	13,222		11,874		10,620	10,000
Average Annual Return, Percent	[42]	22.05%						10.91%							9.44%	[43]
C000160039 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		26.05%						11.17%							9.44%	[43]
C000160041 [Member]
Account Value [Line Items]
Account Value		$ 23,940		23,940		23,940		$ 23,940		23,940	23,940		23,940		$ 23,940		23,940		23,940		23,940		23,940	18,801	19,430		18,819		13,022	13,402	13,588		12,089		10,702	10,000
C000160041 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		27.34%						12.30%							10.54%	[44]
C000172716 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 21,295		21,295		21,295		$ 21,295		21,295	21,295		$ 21,295		$ 21,295		21,295		21,295		21,295		21,295	16,308	17,168		17,480		12,176	12,204	12,361		11,002	10,000
Average Annual Return, Percent	[45]	26.58%						11.52%					10.20%	[46]
C000172716 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		30.58%						11.78%					10.20%	[46]
C000172718 [Member]
Account Value [Line Items]
Account Value		$ 23,022		23,022		23,022		$ 23,022		23,022	23,022		$ 23,022		23,022		23,022		23,022		23,022		23,022	17,453	18,193		18,326		12,640	12,551	12,589		11,091	10,000
C000172718 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		31.91%						12.90%					11.31%	[47]
C000006858 [Member]
Account Value [Line Items]
Account Value		$ 18,338		18,338		18,338		$ 18,338		18,338	18,338		$ 18,338		18,338		18,338		18,338		$ 18,338		18,338	16,115	16,403		17,400		13,970	12,981	12,421		11,524		10,422		10,428		10,000
C000006858 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		13.79%						7.15%													6.25%
C000006862 [Member]
Account Value [Line Items]
Account Value		$ 17,443		17,443		17,443		$ 17,443		17,443	17,443		17,443		17,443		17,443		17,443		$ 17,443		17,443	15,406	15,759		16,809		13,562	12,668	12,178		11,353		10,317		10,383		10,000
C000006862 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		13.22%						6.61%													5.72%
C000006906 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 10,772		10,772		10,772		$ 10,772		10,772	10,772		10,772		10,772		10,772		10,772		$ 10,772		10,772	9,783	10,239		13,663		9,343	10,408	11,550		10,103		8,009		9,338		10,000
Average Annual Return, Percent	[48]	9.11%						0.69%													0.75%
C000006906 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		10.11%						0.69%													0.75%
C000006929 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 15,787		15,787		15,787		$ 15,787		15,787	15,787		15,787		15,787		15,787		15,787		$ 15,787		15,787	13,931	13,817		16,254		11,870	11,628	11,979		10,919		9,311		10,021		10,000
Average Annual Return, Percent	[49]	9.32%						5.99%													4.67%
C000006929 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		13.32%						6.31%													4.67%
C000006931 [Member]
Account Value [Line Items]
Account Value		$ 17,444		17,444		17,444		$ 17,444		17,444	17,444		17,444		17,444		17,444		17,444		$ 17,444		17,444	15,238	14,961		17,424		12,597	12,225	12,463		11,251		9,500		10,116		10,000
C000006931 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		14.48%						7.37%													5.72%
C000006941 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 19,110		19,110		19,110		$ 19,110		19,110	19,110		19,110		19,110		19,110		19,110		$ 19,110		19,110	16,043	15,475		18,283		14,277	12,998	12,710		11,809		10,099		9,940		9,425
Average Annual Return, Percent		12.27%						6.74%													6.69%
C000006941 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		19.12%	[50]					8.01%													7.32%
C000006943 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 18,809		18,809		18,809		$ 18,809		18,809	18,809		18,809		18,809		18,809		18,809		$ 18,809		18,809	15,910	15,462		18,404		14,477	13,282	13,085		12,252		10,556		10,464		10,000
Average Annual Return, Percent	[51]	17.22%						7.21%													6.52%
C000006943 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		18.22%	[52]					7.21%													6.52%
C000071424 [Member]
Account Value [Line Items]
Account Value		$ 10,775		10,775		10,775		$ 10,775		10,775	10,775		10,775		10,775		10,775		10,775		$ 10,775		10,775	9,780	10,237		13,662		9,339	10,402	11,548		10,100		8,007		9,337		10,000
C000071424 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		10.17%						0.71%													0.75%
C000142781 [Member]
Account Value [Line Items]
Account Value		$ 13,194		13,194		13,194		$ 13,194		13,194	13,194		13,194		13,194		$ 13,194		13,194		$ 13,194		13,194	12,128	11,871		12,113		12,155	11,467	10,870		10,563		10,149		10,224	10,000
C000142781 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		8.79%						2.85%									2.83%	[53]
C000160034 [Member]
Account Value [Line Items]
Account Value		$ 19,853		19,853		19,853		$ 19,853		19,853	19,853		19,853		$ 19,853		$ 19,853		19,853		19,853		19,853	16,393	17,996		19,512		12,559	13,965	14,333		11,953		10,368	10,000
C000160034 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		21.11%						7.29%							8.19%	[54]
C000160036 [Member]
Account Value [Line Items]
Account Value		$ 20,738		20,738		20,738		$ 20,738		20,738	20,738		20,738		$ 20,738		20,738		20,738		20,738		20,738	17,031	18,601		20,076		12,850	14,227	14,531		12,055		10,404	10,000
C000160036 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		21.76%						7.83%							8.73%	[55]
C000172719 [Member]
Account Value [Line Items]
Account Value		$ 21,292		21,292		21,292		$ 21,292		21,292	21,292		$ 21,292		$ 21,292		21,292		21,292		21,292		21,292	16,314	17,172		17,473		12,180	12,199	12,361		11,002	10,000
C000172719 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		30.52%						11.78%					10.19%	[56]
C000172721 [Member]
Account Value [Line Items]
Account Value		$ 22,585		22,585		22,585		$ 22,585		22,585	22,585		$ 22,585		22,585		22,585		22,585		22,585		22,585	17,169	17,946		18,116		12,529	12,465	12,528		11,071	10,000
C000172721 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		31.54%						12.62%					11.03%	[57]
C000195688 [Member]
Account Value [Line Items]
Account Value		$ 12,708		12,708		12,708		$ 12,708		12,708	$ 12,708		$ 12,708		12,708		12,708		12,708		12,708		12,708	11,639	11,355		11,551		11,562	10,862	10,280	$ 10,000
C000195688 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		9.18%						3.19%			3.66%	[58]
C000006847 [Member]
Account Value [Line Items]
Account Value		$ 21,020		21,020		21,020		$ 21,020		21,020	$ 21,020		21,020		21,020		21,020		21,020		$ 21,020		21,020	17,652	18,142		19,415		14,129	13,430	13,162		11,758		10,276		10,508		10,000
C000006847 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		19.08%						9.37%													7.71%
C000006849 [Member]
Account Value [Line Items]
Account Value		$ 22,095		22,095		22,095		$ 22,095		22,095	22,095		22,095		22,095		22,095		22,095		$ 22,095		22,095	18,465	18,878		20,105		14,561	13,772	13,427		11,935		10,383		10,561		10,000
C000006849 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		19.66%						9.92%													8.25%
C000006896 [Member]
Account Value [Line Items]
Account Value		$ 14,501		14,501		14,501		$ 14,501		14,501	14,501		14,501		14,501		14,501		14,501		$ 14,501		14,501	13,269	13,592		14,539		12,514	11,776	11,341		10,896		10,190		10,233		10,000
C000006896 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		9.28%						4.25%													3.79%
C000006898 [Member]
Account Value [Line Items]
Account Value		$ 15,238		15,238		15,238		$ 15,238		15,238	15,238		15,238		15,238		15,238		15,238		$ 15,238		15,238	13,886	14,139		15,060		12,891	12,069	11,567		11,060		10,294		10,285		10,000
C000006898 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		9.73%						4.77%													4.30%
C000006911 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 19,246		19,246		19,246		$ 19,246		19,246	19,246		19,246		19,246		19,246		19,246		$ 19,246		19,246	16,405	16,734		17,748		13,446	12,636	12,199		11,063		9,768		9,879		9,425
Average Annual Return, Percent		10.57%						7.50%													6.77%
C000006911 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		17.32%						8.78%													7.40%
C000006916 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 18,948		18,948		18,948		$ 18,948		$ 18,948	18,948		18,948		18,948		18,948		18,948		$ 18,948		$ 18,948	16,276	16,725		17,868		13,637	12,919	12,562		11,480		10,210		10,403		10,000
Average Annual Return, Percent	[59]	12.42%								7.66%													6.60%
C000006916 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		16.42%								7.96%													6.60%
C000006920 [Member]
Account Value [Line Items]
Account Value		$ 18,954		18,954		18,954		$ 18,954		$ 18,954	18,954		18,954		18,954		18,954		18,954		$ 18,954		$ 18,954	16,275	16,722		17,875		13,644	12,922	12,563		11,483		10,209		10,408		10,000
C000006920 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		16.46%						7.96%													6.60%
C000006937 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 17,598		17,598		17,598		$ 17,598		17,598	17,598		17,598		17,598		17,598		17,598		$ 17,598		17,598	15,698	14,793		16,915		12,361	11,858	11,935		10,605		8,935		9,449		9,425
Average Annual Return, Percent		5.66%						6.94%													5.81%
C000006937 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		12.11%						8.22%													6.44%
C000006938 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 17,318		17,318		17,318		$ 17,318		17,318	17,318		17,318		17,318		17,318		17,318		$ 17,318		17,318	15,566	14,781		17,027		12,536	12,119	12,287		11,001		9,340		9,949		10,000
Average Annual Return, Percent	[60]	7.25%						7.10%													5.65%
C000006938 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		11.25%						7.40%													5.65%
C000142775 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 12,553		12,553		12,553		$ 12,553		12,553	12,553		12,553		12,553		$ 12,553		12,553		$ 12,553		12,553	11,540	11,289		11,520		11,562	10,876	10,300		9,992		9,600		9,657	9,425
Average Annual Return, Percent		2.52%						1.70%									2.32%	[61]
C000142775 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		8.78%						2.91%									2.93%	[61]
C000142776 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 12,241		12,241		12,241		$ 12,241		12,241	12,241		12,241		12,241		$ 12,241		12,241		12,241		12,241	11,340	11,174		11,485		11,630	11,040	10,553		10,335		10,005		10,145	10,000
Average Annual Return, Percent	[62]	3.95%						1.72%									2.06%	[63]
C000142776 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		7.95%						2.09%									2.06%	[63]
C000160026 [Member]
Account Value [Line Items]
Account Value		$ 32,955		32,955		32,955		$ 32,955		32,955	32,955		32,955		$ 32,955		$ 32,955		32,955		32,955		32,955	23,842	22,810		24,486		18,024	14,494	14,354		12,141		10,279	10,000
C000160026 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		38.22%						17.85%							14.67%	[64]
C000160029 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 19,140		19,140		19,140		$ 19,140		19,140	19,140		19,140		$ 19,140		19,140		19,140		19,140		19,140	15,768	17,261		18,663		11,983	13,295	13,615		11,323		9,792	9,425
Average Annual Return, Percent		14.40%						6.29%							7.74%	[65]
C000160029 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		21.38%						7.56%							8.47%	[65]
C000160043 [Member]
Account Value [Line Items]
Account Value		$ 22,929		22,929		22,929		$ 22,929		22,929	22,929		22,929		$ 22,929		22,929		22,929		22,929		22,929	18,097	18,809		18,296		12,720	13,156	13,404		11,976		10,656	10,000
C000160043 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		26.70%						11.75%							9.99%	[66]
C000160044 [Member]
Account Value [Line Items]
Account Value		$ 23,440		23,440		23,440		$ 23,440		23,440	23,440		23,440		$ 23,440		23,440		23,440		23,440		23,440	18,455	19,121		18,560		12,874	13,284	13,504		12,032		10,674	10,000
C000160044 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		27.01%						12.03%							10.27%	[67]
C000220107 [Member]
Account Value [Line Items]
Account Value		$ 15,791		15,791		$ 15,791		$ 15,791		15,791	15,791		15,791		$ 15,791		15,791		15,791		15,791		15,791	13,365	13,007		13,828	10,000
C000220107 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		18.15%				12.36%	[68]
C000220108 [Member]
Account Value [Line Items]
Account Value		$ 15,619		15,619		$ 15,619		15,619		15,619	15,619		15,619		15,619		15,619		15,619		15,619		15,619	13,248	12,924		13,775	10,000
C000220108 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		17.89%				12.05%	[69]
C000006843 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 21,020		21,020		$ 21,020		$ 21,020		21,020	21,020		21,020		21,020		21,020		21,020		$ 21,020		21,020	17,655	18,142		19,412		14,129	13,434	13,166		11,754		10,275		10,512		10,000
Average Annual Return, Percent	[70]	15.06%						9.09%													7.71%
C000006843 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		19.06%						9.37%													7.71%
C000006892 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 14,492		14,492		14,492		$ 14,492		14,492	14,492		14,492		14,492		14,492		14,492		$ 14,492		14,492	13,274	13,582		14,538		12,514	11,771	11,339		10,890		10,190		10,234		10,000
Average Annual Return, Percent	[71]	5.18%						3.91%													3.78%
C000006892 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		9.18%						4.25%													3.78%
C000006936 [Member]
Account Value [Line Items]
Account Value		$ 17,010		17,010		17,010		$ 17,010		17,010	17,010		17,010		17,010		17,010		17,010		$ 17,010		17,010	14,897	14,663		17,120		12,411	12,069	12,334		11,168		9,449		10,089		10,000
C000006936 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		14.19%						7.10%													5.46%
C000071426 [Member]
Account Value [Line Items]
Account Value		$ 11,616		11,616		11,616		$ 11,616		11,616	11,616		11,616		11,616		11,616		11,616		$ 11,616		11,616	10,464	10,876		14,401		9,774	10,806	11,903		10,333		8,130		9,407		10,000
C000071426 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		11.01%						1.46%													1.51%
C000071431 [Member]
Account Value [Line Items]
Account Value		$ 17,319		17,319		17,319		$ 17,319		17,319	17,319		17,319		17,319		17,319		17,319		$ 17,319		17,319	15,567	14,783		17,028		12,536	12,117	12,288		11,001		9,341		9,951		10,000
C000071431 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		11.25%						7.40%													5.65%
C000071436 [Member]
Account Value [Line Items]
Account Value		$ 20,273		20,273		20,273		$ 20,273		20,273	20,273		20,273		20,273		20,273		20,273		$ 20,273		20,273	17,020	16,418		19,397		15,143	13,790	13,483		12,530		10,715		10,545		10,000
C000071436 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R3 without sales charge
Average Annual Return, Percent		19.12%	[72]					8.01%													7.32%
C000142779 [Member]
Account Value [Line Items]
Account Value		$ 12,241		12,241		12,241		$ 12,241		12,241	12,241		12,241		12,241		$ 12,241		12,241		$ 12,241		12,241	11,340	11,184		11,495		11,630	11,039	10,553		10,335		10,005		10,155	10,000
C000142779 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		7.95%						2.09%									2.06%	[73]
C000160022 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 30,867		30,867		30,867		$ 30,867		30,867	30,867		30,867		$ 30,867		$ 30,867		30,867		30,867		30,867	22,504	21,687		23,466		17,394	14,092	14,074		11,978		10,226	10,000
Average Annual Return, Percent	[74]	36.16%						16.98%							13.81%	[75]
C000160022 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		37.16%						16.98%							13.81%	[75]
C000160033 [Member]
Account Value [Line Items]
Account Value		$ 19,018		19,018		19,018		$ 19,018		19,018	19,018		19,018		$ 19,018		19,018		19,018		19,018		19,018	15,772	17,398		18,965		12,264	13,716	14,140		11,855		10,333	10,000
C000160033 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R1 without sales charge
Average Annual Return, Percent		20.58%						6.76%							7.66%	[76]
C000160040 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 21,942		21,942		21,942		$ 21,942		21,942	21,942		21,942		$ 21,942		21,942		21,942		21,942		21,942	17,418	18,182		17,776		12,423	12,908	13,215		11,870		10,616	10,000
Average Annual Return, Percent	[77]	24.97%						11.19%							9.44%	[78]
C000160040 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		25.97%						11.19%							9.44%	[78]
C000172715 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 21,277		21,277		21,277		$ 21,277		21,277	21,277		$ 21,277		$ 21,277		21,277		21,277		21,277		21,277	16,182	16,909		17,080		11,811	11,751	11,813		10,435	9,425
Average Annual Return, Percent		23.93%						11.28%					10.18%	[79]
C000172715 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		31.49%						12.61%					11.03%	[79]
C000220111 [Member]
Account Value [Line Items]
Account Value		$ 15,787		15,787		$ 15,787		$ 15,787		15,787	15,787		$ 15,787		15,787		15,787		15,787		15,787		15,787	13,361	12,987		13,808	10,000
C000220111 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		18.16%				12.35%	[80]
C000231058 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Account Value		$ 10,969		$ 10,969		$ 10,969		10,969		10,969	10,969		10,969		10,969		10,969		10,969		10,969		10,969	9,112	9,265	10,000
C000231058 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Average Annual Return, Percent		20.37%		3.53%	[81]
C000231060 [Member]
Account Value [Line Items]
Account Value		$ 10,142		$ 10,142		10,142		10,142		10,142	10,142		10,142		10,142		10,142		10,142		10,142		10,142	9,186	9,305	10,000
C000231060 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		10.41%		0.53%	[82]
C000231061 [Member]
Account Value [Line Items]
Account Value		$ 10,737		$ 10,737		10,737		10,737		10,737	10,737		10,737		10,737		10,737		10,737		10,737		10,737	9,120	9,273	10,000
C000231061 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		17.73%		2.70%	[83]
C000006852 [Member]
Account Value [Line Items]
Account Value		$ 18,332		$ 18,332		18,332		$ 18,332		18,332	18,332		18,332		18,332		18,332		18,332		$ 18,332		18,332	16,113	16,397		17,403		13,972	12,982	12,421		11,525		10,422		10,434		10,000
C000006852 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		13.77%						7.14%													6.25%
C000006887 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 14,730		14,730		14,730		$ 14,730		14,730	14,730		14,730		14,730		14,730		14,730		$ 14,730		14,730	13,384	13,603		14,449		12,339	11,524	11,017		10,501		9,749		9,723		9,425
Average Annual Return, Percent		3.73%						3.80%													3.95%
C000006887 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		10.05%						5.03%													4.57%
C000006888 [Member]
Account Value [Line Items]
Account Value		$ 16,026		16,026		16,026		$ 16,026		16,026	16,026		16,026		16,026		16,026		16,026		$ 16,026		16,026	14,527	14,726		15,595		13,288	12,380	11,806		11,225		10,395		10,342		10,000
C000006888 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		10.32%						5.30%													4.83%
C000006904 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A with initial sales charge (5.75%)
Account Value		$ 10,952		10,952		10,952		$ 10,952		10,952	10,952		10,952		10,952		10,952		10,952		$ 10,952		10,952	9,868	10,252		13,580		9,216	10,189	11,223		9,742		7,664		8,869		9,425
Average Annual Return, Percent		4.60%						0.26%													0.91%
C000006904 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		A without sales charge
Average Annual Return, Percent		10.99%						1.46%													1.51%
C000006925 [Member]
Account Value [Line Items]
Account Value		$ 17,448		17,448		17,448		$ 17,448		17,448	17,448		17,448		17,448		17,448		17,448		$ 17,448		17,448	15,247	14,968		17,428		12,603	12,231	12,466		11,255		9,505		10,123		10,000
C000006925 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		14.43%						7.36%													5.72%
C000006935 [Member]
Account Value [Line Items]
Account Value		$ 16,595		16,595		16,595		$ 16,595		16,595	16,595		16,595		16,595		16,595		16,595		$ 16,595		16,595	14,573	14,377		16,831		12,232	11,922	12,216		11,085		9,409		10,068		10,000
C000006935 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		13.88%						6.84%													5.20%
C000006940 [Member]
Account Value [Line Items]
Account Value		$ 19,144		19,144		19,144		$ 19,144		19,144	19,144		19,144		19,144		19,144		19,144		$ 19,144		19,144	17,037	16,016		18,267		13,314	12,740	12,789		11,337		9,530		10,051		10,000
C000006940 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		12.36%						8.49%													6.71%
C000071430 [Member]
Account Value [Line Items]
Account Value		$ 19,140		19,140		19,140		$ 19,140		19,140	19,140		19,140		19,140		19,140		19,140		$ 19,140		19,140	17,034	16,012		18,262		13,310	12,739	12,790		11,338		9,530		10,052		10,000
C000071430 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R4 without sales charge
Average Annual Return, Percent		12.37%						8.48%													6.71%
C000071432 [Member]
Account Value [Line Items]
Account Value		$ 18,210		18,210		18,210		$ 18,210		18,210	18,210		18,210		18,210		18,210		18,210		$ 18,210		18,210	16,286	15,387		17,634		12,919	12,427	12,538		11,168		9,433		10,003		10,000
C000071432 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		11.81%	[84]					7.94%													6.18%
C000160021 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 30,871		30,871		30,871		$ 30,871		30,871	30,871		30,871		$ 30,871		30,871		30,871		$ 30,871		30,871	22,510	21,693		23,471		17,401	14,099	14,075		11,989		10,227	10,000
Average Annual Return, Percent	[85]	33.14%						16.75%							13.81%	[86]
C000160021 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		37.14%						16.97%							13.81%	[86]
C000160023 [Member]
Account Value [Line Items]
Account Value		$ 33,678		33,678		33,678		$ 33,678		33,678	33,678		33,678		$ 33,678		33,678		33,678		33,678		33,678	24,305	23,189		24,843		18,236	14,623	14,453		12,189		10,297	10,000
C000160023 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		38.56%						18.16%							14.96%	[87]
C000160025 [Member]
Account Value [Line Items]
Account Value		$ 32,239		32,239		32,239		$ 32,239		32,239	32,239		32,239		$ 32,239		32,239		32,239		32,239		32,239	23,392	22,433		24,139		17,812	14,353	14,266		12,085		10,261	10,000
C000160025 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R2 without sales charge
Average Annual Return, Percent		37.82%						17.57%							14.38%	[88]
C000160030 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B with CDSC (declining over six years from 4% to 0%)
Account Value		$ 19,012		19,012		19,012		$ 19,012		19,012	19,012		19,012		$ 19,012		19,012		19,012		19,012		19,012	15,780	17,405		18,961		12,272	13,717	14,142		11,846		10,334	10,000
Average Annual Return, Percent	[89]	16.48%						6.44%							7.65%	[90]
C000160030 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		B without sales charge
Average Annual Return, Percent		20.48%						6.75%							7.65%	[90]
C000160032 [Member]
Account Value [Line Items]
Account Value		$ 20,740		20,740		20,740		$ 20,740		20,740	20,740		20,740		$ 20,740		20,740		20,740		20,740		20,740	17,045	18,604		20,088		12,863	14,238	14,537		12,056		10,414	10,000
C000160032 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		I without sales charge
Average Annual Return, Percent		21.68%						7.81%							8.73%	[91]
C000172723 [Member]
Account Value [Line Items]
Account Value		$ 23,171		23,171		23,171		$ 23,171		23,171	23,171		$ 23,171		$ 23,171		23,171		23,171		23,171		23,171	17,550	18,276		18,386		12,678	12,569	12,591		11,091	10,000
C000172723 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		R6 without sales charge
Average Annual Return, Percent		32.03%						13.01%					11.40%	[92]
C000220112 [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C with CDSC (1% for 12 months)
Account Value		$ 15,152		15,152		$ 15,152		$ 15,152		15,152	15,152		$ 15,152		15,152		15,152		15,152		15,152		15,152	12,948	12,731		13,671	10,000
Average Annual Return, Percent	[93]	16.02%				11.18%	[94]
C000220112 [Member] | Without Sales Load [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		C without sales charge
Average Annual Return, Percent		17.02%				11.18%	[94]
ICE BofA 0 3 Month U S Treasury Bill Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		ICE BofA 0-3 Month U.S. Treasury Bill Index
Account Value		$ 11,549		11,549		$ 11,549		$ 11,549		11,549	11,549		11,549		11,549		$ 11,549		11,549		11,549		11,549	10,947	10,596		10,582		10,572	10,400	10,172		10,050		10,011		10,001	$ 10,000
Average Annual Return, Percent	[95],[96]	5.50%						2.12%									1.46%	[61]
Bloomberg U S Aggregate Bond Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Bloomberg U.S. Aggregate Bond Index
Account Value		$ 11,329		$ 11,329		11,329		$ 11,329		11,329	11,329		11,329		11,329		$ 11,329		11,329		$ 11,329		11,329	11,183	11,428	10,000	12,452		12,502	11,426	10,739		10,780		10,612		10,303		10,000
Average Annual Return, Percent		1.31%	[97]	(3.74%)	[82],[98]			(0.17%)	[97]												1.26%	[97]
MSCI EAFE Europe Australasia Far East Value Index net div [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MSCI EAFE (Europe, Australasia, Far East) Value Index (net div)
Account Value		$ 16,187		$ 16,187		$ 16,187		$ 16,187		16,187	16,187		16,187		16,187		16,187		16,187		$ 16,187		16,187	13,098	13,088		13,699	10,000
Average Annual Return, Percent	[99],[100]	23.58%				13.06%	[35]
MSCI All Country World ex US Index net div [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MSCI All Country World (ex-US) Index (net div)
Account Value		$ 14,838		14,838		$ 14,838		$ 14,838		14,838	14,838		14,838		14,838		14,838		14,838		$ 14,838		14,838	12,710	12,891		14,717		10,308	10,675	11,387		10,383		8,781		9,910		10,000
Average Annual Return, Percent	[101],[102]	16.74%						6.81%													4.03%
Russell 2000 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Russell 2000® Index
Account Value		$ 20,227		20,227		20,227		$ 20,227		20,227	20,227		20,227		$ 20,227		20,227		20,227		$ 20,227		20,227	16,839	17,666		21,263		12,921	13,381	14,711		12,182		10,121	10,000
Average Annual Return, Percent	[103],[104]	20.12%						8.61%							8.42%	[65]
MSCI EAFE Europe Australasia Far East Index net div [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MSCI EAFE (Europe, Australasia, Far East) Index (net div)
Account Value		$ 15,686		15,686		$ 15,686		$ 15,686		15,686	15,686		15,686		$ 15,686		15,686		15,686		$ 15,686		15,686	13,234	12,841		14,328	$ 10,000	10,352	10,651	11,301		10,466		8,989		9,952		10,000
Average Annual Return, Percent		18.53%	[105]			10.31%	[35],[99],[100]	8.05%	[105]												4.60%	[105]
Russell 3000 Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Russell 3000® Index
Account Value		$ 26,584		26,584		$ 26,584		$ 26,584		26,584	26,584		$ 26,584		$ 26,584		26,584		26,584		$ 26,584		26,584	20,837	20,421		21,202		14,733	13,218	12,896		11,208	10,000	10,754	10,000
Average Annual Return, Percent		27.58%	[106],[107]					15%	[106],[107]				13.37%	[79],[106],[107]	13.44%	[65],[103],[104]
MSCI All Country World ex US Growth Index net div [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MSCI All Country World (ex-US) Growth Index (net div)
Account Value		$ 15,967		15,967		15,967		$ 15,967		15,967	15,967		$ 15,967		$ 15,967		15,967		15,967		$ 15,967		15,967	14,130	14,097		17,384		12,424	11,571	12,217		10,931		9,356		10,201		10,000
Average Annual Return, Percent	[101],[102]	13.01%						6.65%													4.79%
Russell 1000 Growth Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Russell 1000® Growth Index
Account Value		$ 39,547		39,547		39,547		$ 39,547		39,547	39,547		39,547		$ 39,547		39,547		39,547		$ 39,547		39,547	29,601	27,021		28,823		20,599	16,316	15,481		12,792		10,636	10,000
Average Annual Return, Percent	[108],[109]	33.60%						19.37%							17.08%	[7]
Standard And Poors 500 Stock Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Standard & Poor's 500 Stock Index
Account Value		$ 33,028		$ 33,028		33,028		$ 33,028		33,028	33,028		33,028		$ 33,028		33,028		33,028		$ 33,028		33,028	25,766	25,034	10,000	25,109		17,895	15,859	15,281		13,359		11,372		11,181		10,000
Average Annual Return, Percent		28.19%	[110]	9.13%	[81],[111]			15.80%	[110]												12.69%	[110]
MSCI Emerging Markets Index net div [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MSCI Emerging Markets Index (net div)
Account Value		$ 13,007		$ 13,007		13,007		$ 13,007		13,007	13,007		13,007		13,007		13,007		13,007		$ 13,007		13,007	11,573	12,646		15,774		10,446	10,925	11,966		10,494		8,236		9,999		10,000
Average Annual Return, Percent	[112]	12.39%						3.55%													2.66%
Russell 1000 Value Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Russell 1000® Value Index
Account Value		$ 23,054		23,054		23,054		$ 23,054		23,054	23,054		23,054		$ 23,054		23,054		23,054		$ 23,054		23,054	18,942	19,844		19,661		13,617	13,844	13,646		12,607		10,995	$ 10,000
Average Annual Return, Percent	[113],[114]	21.71%						10.74%							10.06%	[31]
Russell Midcap Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		Russell Midcap® Index
Account Value		$ 21,273		21,273		21,273		$ 21,273		21,273	21,273		$ 21,273		$ 21,273		21,273		21,273		21,273		21,273	17,279	18,096		19,411		12,916	12,586	12,389		10,996	$ 10,000
Average Annual Return, Percent	[106],[107]	23.11%						11.07%					10.18%	[79]
MFS Conservative Allocation Fund Blended Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MFS Conservative Allocation Fund Blended Index
Account Value		$ 16,137		$ 16,137		16,137		$ 16,137		16,137	16,137		$ 16,137		16,137		16,137		16,137		$ 16,137		16,137	14,656	14,770	10,000	15,566		13,592	12,497	11,943		11,419		10,668		10,496		10,000
Average Annual Return, Percent		10.10%	[97]	0.73%	[82],[98]			5.25%	[97]												4.90%	[97]
MFS Aggressive Growth Allocation Fund Blended Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MFS Aggressive Growth Allocation Fund Blended Index
Account Value		$ 23,897		$ 23,897		23,897		$ 23,897		23,897	23,897		23,897		23,897		23,897		23,897		$ 23,897		23,897	19,372	19,236	10,000	19,570		13,984	13,344	13,307		11,898		10,304		10,571		10,000
Average Annual Return, Percent		23.36%	[110]	6.83%	[81],[111]			12.36%	[110]												9.10%	[110]
MFS Moderate Allocation Fund Blended Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MFS Moderate Allocation Fund Blended Index
Account Value		$ 18,788		$ 18,788		18,788		$ 18,788		18,788	18,788		18,788		18,788		18,788		18,788		$ 18,788		18,788	16,392	16,425	$ 10,000	17,057		13,914	12,883	12,447		11,614		10,580		10,531		10,000
Average Annual Return, Percent		14.62%	[115]	2.89%	[36],[116]			7.84%	[115]												6.51%	[115]
MFS Growth Allocation Fund Blended Index [Member]
Account Value [Line Items]
Line Graph and Table Measure Name		MFS Growth Allocation Fund Blended Index
Account Value		$ 21,495		$ 21,495		$ 21,495		$ 21,495		$ 21,495	$ 21,495		$ 21,495		$ 21,495		$ 21,495		$ 21,495		$ 21,495		$ 21,495	$ 18,052	$ 18,001		$ 18,469		$ 14,091	$ 13,203	$ 12,934		$ 11,803		$ 10,482		$ 10,569		$ 10,000
Average Annual Return, Percent		19.07%	[117]	4.93%	[83],[118]			10.24%	[117]												7.95%	[117]
[1]Assuming redemption at the end of the applicable period.[2]Assuming redemption at the end of the applicable period.[3]Assuming redemption at the end of the applicable period.[4]Assuming redemption at the end of the applicable period.[5]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.16%.[6]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[7]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[8]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[9]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[10]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[11]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[12]Assuming redemption at the end of the applicable period.[13]Assuming redemption at the end of the applicable period.[14]Assuming redemption at the end of the applicable period.[15]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.48%.[16]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.38%.[17]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[18]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[19]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[20]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[21]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[22]For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2024.[23]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[24]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[25]Assuming redemption at the end of the applicable period.[26]Assuming redemption at the end of the applicable period.[27]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[28]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[29]Assuming redemption at the end of the applicable period.[30]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[31]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[32]Assuming redemption at the end of the applicable period.[33]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[34]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[35]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[36]For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024.[37]Assuming redemption at the end of the applicable period.[38]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.38%.[39]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.75%.[40]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[41]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[42]Assuming redemption at the end of the applicable period.[43]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[44]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[45]Assuming redemption at the end of the applicable period.[46]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[47]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[48]Assuming redemption at the end of the applicable period.[49]Assuming redemption at the end of the applicable period.[50]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.09%.[51]Assuming redemption at the end of the applicable period.[52]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 18.19%.[53]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[54]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[55]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[56]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[57]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[58]For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2024.[59]Assuming redemption at the end of the applicable period.[60]Assuming redemption at the end of the applicable period.[61]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[62]Assuming redemption at the end of the applicable period.[63]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[64]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[65]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[66]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[67]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[68]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[69]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[70]Assuming redemption at the end of the applicable period.[71]Assuming redemption at the end of the applicable period.[72]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 19.09%.[73]For the period from the commencement of the class's investment operations, June 27, 2014 through May 31, 2024.[74]Assuming redemption at the end of the applicable period.[75]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[76]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[77]Assuming redemption at the end of the applicable period.[78]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[79]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[80]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[81]For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024.[82]For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024.[83]For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2024.[84]If the 1-year without sales charge return included adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the return would be 11.78%.[85]Assuming redemption at the end of the applicable period.[86]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[87]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[88]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[89]Assuming redemption at the end of the applicable period.[90]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[91]For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2024.[92]For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2024.[93]Assuming redemption at the end of the applicable period.[94]For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2024.[95]Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the ICE BofA 0-3 Month U.S. Treasury Bill Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the ICE BofA 0-3 Month U.S. Treasury Bill Index as an additional benchmark that MFS believes corresponds to the fund’s investment strategies.[96]Source: FactSet Research Systems Inc.[97]Source: FactSet Research Systems Inc.[98]Source: FactSet Research Systems Inc.[99]Effective May 1, 2024, the MSCI EAFE (Europe, Australasia, Far East) Index (net div) replaced the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI EAFE (Europe, Australasia, Far East) Value Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[100]Source: FactSet Research Systems Inc.[101]Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[102]Source: FactSet Research Systems Inc.[103]Effective May 1, 2024, the Russell 3000® Index replaced the Russell 2000® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 2000® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[104]Source: FactSet Research Systems Inc.[105]Source: FactSet Research Systems Inc.[106]Effective May 1, 2024, the Russell 3000® Index replaced the Russell Midcap® Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell Midcap® Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[107]Source: FactSet Research Systems Inc.[108]Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Growth Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Growth Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[109]Source: FactSet Research Systems Inc.[110]Source: FactSet Research Systems Inc.[111]Source: FactSet Research Systems Inc.[112]Source: FactSet Research Systems Inc.[113]Effective May 1, 2024, the Russell 3000® Index replaced the Russell 1000® Value Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Russell 1000® Value Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[114]Source: FactSet Research Systems Inc.[115]Source: FactSet Research Systems Inc.[116]Source: FactSet Research Systems Inc.[117]Source: FactSet Research Systems Inc.[118]Source: FactSet Research Systems Inc.

Shareholder Report, Holdings (D

Shareholder Report, Holdings (Details)	May 31, 2024
C000006857 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006857 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006857 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006857 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006857 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006857 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006857 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006857 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006857 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006857 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006857 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006857 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006857 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006857 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006857 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006857 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006857 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006857 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006857 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006857 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006857 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006857 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006857 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006857 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006857 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006857 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006857 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006857 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006860 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006860 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006860 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006860 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006860 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006860 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006860 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006860 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006860 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006860 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006860 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006860 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006860 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006860 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006860 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006860 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006860 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006860 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006860 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006860 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006860 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006860 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006860 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006860 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006860 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006860 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006860 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006860 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006863 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006863 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006863 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006863 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006863 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006863 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006863 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006863 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006863 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006863 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006863 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006863 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006863 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006863 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006863 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006863 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006863 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006863 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006863 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006863 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006863 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006863 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006863 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006863 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006863 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006863 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006863 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006863 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006905 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006905 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006905 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006905 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000006905 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000006905 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006905 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006905 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000006905 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006905 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006905 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006905 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000006905 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006905 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006905 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006905 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006905 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006905 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000006905 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006905 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000006905 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000006905 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006907 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006907 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006907 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006907 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000006907 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000006907 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006907 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006907 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000006907 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006907 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006907 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006907 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000006907 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006907 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006907 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006907 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006907 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006907 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000006907 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006907 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000006907 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000006907 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006924 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006924 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006924 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006924 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006924 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006924 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006924 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006924 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006924 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006924 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006930 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006930 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006930 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006930 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006930 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006930 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006930 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006930 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006930 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006930 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006942 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006942 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006942 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006942 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000006942 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006942 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006942 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006942 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000006942 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006942 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006942 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006942 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006942 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006942 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006942 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006942 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000006942 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000006942 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000006942 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006942 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000006942 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000006942 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000034484 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000034484 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000034484 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000034484 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000034484 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000034484 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000034484 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000034484 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000034484 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000034484 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000034484 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000034484 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000034484 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000034484 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000034484 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000034484 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000034484 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000034484 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000034484 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000034484 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000034484 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000034484 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000142782 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[1]
C000142782 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[1]
C000142782 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[1]
C000142782 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[1],[2]
C000142782 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[3]
C000142782 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[1]
C000142782 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[3]
C000142782 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[4]
C000142782 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[3]
C000142782 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[4]
C000142782 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[1]
C000142782 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[4]
C000142782 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[1],[5]
C000142782 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[1]
C000142782 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[4]
C000142782 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[4]
C000142782 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[4]
C000142782 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[4]
C000160020 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160020 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160020 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160020 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160020 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160020 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160020 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160020 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160020 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160020 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160020 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160020 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160020 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160020 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160020 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160020 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160020 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160020 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160020 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160020 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160020 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160020 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160020 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160035 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160035 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160035 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160035 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160035 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160035 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160035 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160035 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160035 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160035 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160035 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160035 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160035 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160035 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160035 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160035 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160035 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160035 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160035 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160035 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160035 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160035 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160035 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160037 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160037 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160037 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160037 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160037 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160037 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160037 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160037 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160037 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160037 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160037 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160037 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160037 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160037 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160037 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160037 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160037 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160037 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160037 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160037 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160037 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160037 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160037 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000172720 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172720 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172720 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172720 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172720 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172720 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172720 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172720 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172720 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172720 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172720 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172720 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172720 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172720 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172720 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172720 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172720 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172720 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000172722 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172722 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172722 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172722 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172722 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172722 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172722 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172722 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172722 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172722 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172722 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172722 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172722 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172722 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172722 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172722 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172722 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172722 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000006845 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006845 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006845 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006845 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006845 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006845 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006845 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006845 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006845 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006845 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006845 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006845 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006845 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006845 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006845 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006845 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006845 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006845 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006845 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006845 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006850 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006850 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006850 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006850 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006850 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006850 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006850 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006850 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006850 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006850 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006850 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006850 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006850 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006850 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006850 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006850 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006850 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006850 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006850 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006850 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006893 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006893 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006893 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006893 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006893 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006893 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006893 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006893 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006893 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006893 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006893 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006893 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006893 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006893 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006893 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006893 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006893 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006893 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006893 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006893 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006893 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006893 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006893 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006893 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006893 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006893 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006893 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006894 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006894 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006894 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006894 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006894 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006894 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006894 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006894 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006894 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006894 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006894 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006894 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006894 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006894 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006894 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006894 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006894 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006894 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006894 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006894 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006894 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006894 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006894 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006894 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006894 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006894 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006894 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006917 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006917 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006917 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006917 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006917 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006917 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006917 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006917 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006917 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006917 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006917 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006917 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006917 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006917 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006917 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006917 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006917 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006917 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006917 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006917 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006917 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006917 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006917 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006917 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006917 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006917 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006917 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006918 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006918 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006918 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006918 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006918 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006918 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006918 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006918 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006918 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006918 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006918 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006918 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006918 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006918 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006918 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006918 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006918 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006918 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006918 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006918 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006918 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006918 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006918 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006918 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006918 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006918 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006918 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006939 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006939 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006939 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006939 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006939 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006939 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000006939 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006939 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006939 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006939 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006939 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000006939 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000006939 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000006939 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000006939 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000006939 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006939 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000006939 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000006939 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006939 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006939 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000006939 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000034485 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000034485 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000034485 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000034485 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000034485 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000034485 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000034485 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000034485 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000034485 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000034485 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000034485 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000034485 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000034485 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000034485 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000034485 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000034485 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000034485 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000034485 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000034485 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000034485 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000034485 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000034485 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071437 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071437 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071437 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071437 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000071437 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071437 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000071437 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071437 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000071437 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071437 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071437 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000071437 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000071437 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000071437 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000071437 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071437 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000071437 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000071437 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000071437 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000071437 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000071437 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000071437 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160027 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160027 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160027 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160027 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160027 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160027 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160027 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160027 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160027 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160027 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160027 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160027 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160027 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160027 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160027 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160027 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160027 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160027 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160027 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160027 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160027 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160027 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160027 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160028 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160028 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160028 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160028 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160028 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160028 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160028 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160028 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160028 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160028 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160028 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160028 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160028 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160028 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160028 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160028 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160028 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160028 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160028 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160028 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160028 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160028 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160028 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160042 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160042 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160042 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160042 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160042 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160042 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160042 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160042 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160042 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160042 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160042 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160042 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160042 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160042 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160042 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160042 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160042 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160042 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160042 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160042 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160042 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160042 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160042 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160045 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160045 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160045 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160045 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160045 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160045 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160045 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160045 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160045 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160045 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160045 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160045 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160045 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160045 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160045 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160045 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160045 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160045 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160045 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160045 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160045 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160045 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160045 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160046 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160046 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160046 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160046 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160046 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160046 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160046 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160046 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160046 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160046 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160046 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160046 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160046 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160046 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160046 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160046 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160046 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160046 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160046 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160046 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160046 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160046 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160046 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000195683 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000195683 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000195683 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000195683 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000195683 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000195683 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000195683 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000195683 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000195683 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000195683 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000220110 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220110 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220110 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220110 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220110 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220110 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220110 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220110 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220110 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220110 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220110 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220110 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220110 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220110 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220110 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220110 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220110 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220110 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220110 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220110 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220110 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220110 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220113 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220113 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220113 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220113 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220113 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220113 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220113 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220113 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220113 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220113 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220113 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220113 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220113 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220113 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220113 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220113 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220113 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220113 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220113 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220113 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220113 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220113 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006856 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006856 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006856 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006856 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006856 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006856 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006856 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006856 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006856 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006856 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006856 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006856 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006856 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006856 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006856 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006856 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006856 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006856 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006856 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006856 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006856 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006856 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006856 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006856 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006856 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006856 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006856 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006856 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006899 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006899 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006899 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006899 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006899 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006899 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006899 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006899 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006899 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006899 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006899 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006899 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006899 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006899 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006899 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006899 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006899 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006899 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006899 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006899 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006899 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006899 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006899 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006899 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006899 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006899 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006899 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006923 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006923 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006923 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006923 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006923 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006923 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006923 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006923 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006923 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006923 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006923 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006923 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006923 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006923 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006923 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006923 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006923 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006923 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006923 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006923 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006923 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006923 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006923 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006923 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006923 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006923 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006923 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006933 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006933 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006933 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006933 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006933 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006933 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006933 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006933 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006933 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006933 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000071428 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071428 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071428 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071428 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000071428 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000071428 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071428 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071428 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000071428 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071428 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071428 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000071428 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000071428 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071428 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000071428 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071428 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071428 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000071428 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000071428 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071428 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000071428 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000071428 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071433 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071433 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071433 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071433 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000071433 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071433 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000071433 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071433 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071433 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071433 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071433 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000071433 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000071433 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000071433 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000071433 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000071433 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071433 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000071433 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000071433 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000071433 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071433 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000071433 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000071434 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071434 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071434 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071434 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000071434 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071434 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000071434 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071434 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000071434 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071434 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071434 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000071434 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000071434 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000071434 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000071434 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071434 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000071434 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000071434 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000071434 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000071434 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000071434 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000071434 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000142777 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[6]
C000142777 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[6]
C000142777 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[6]
C000142777 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[6],[7]
C000142777 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[8]
C000142777 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[6]
C000142777 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[8]
C000142777 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[9]
C000142777 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[8]
C000142777 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[9]
C000142777 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[6]
C000142777 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[9]
C000142777 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[6],[10]
C000142777 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[6]
C000142777 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[9]
C000142777 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[9]
C000142777 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[9]
C000142777 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[9]
C000160024 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160024 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160024 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160024 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160024 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160024 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160024 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160024 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160024 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160024 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160024 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160024 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160024 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160024 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160024 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160024 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160024 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160024 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160024 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160024 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160024 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160024 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160024 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160031 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160031 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160031 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160031 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160031 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160031 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160031 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160031 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160031 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160031 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160031 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160031 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160031 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160031 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160031 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160031 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160031 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160031 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160031 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160031 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160031 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160031 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160031 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160038 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160038 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160038 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160038 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160038 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160038 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160038 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160038 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160038 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160038 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160038 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160038 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160038 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160038 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160038 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160038 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160038 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160038 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160038 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160038 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160038 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160038 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160038 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172717 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172717 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172717 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172717 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172717 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172717 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172717 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172717 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172717 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172717 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172717 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172717 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172717 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172717 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172717 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172717 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172717 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000220106 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220106 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220106 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220106 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220106 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220106 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220106 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220106 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220106 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220106 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220106 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220106 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220106 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220106 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220106 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220106 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220106 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220106 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220106 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220106 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220106 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220106 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220109 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220109 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220109 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220109 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220109 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220109 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220109 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220109 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220109 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220109 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220109 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220109 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220109 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220109 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220109 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220109 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220109 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220109 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220109 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220109 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220109 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220109 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000231059 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000231059 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000231059 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000231059 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000231059 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231059 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231059 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231059 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231059 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000231059 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231059 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231059 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000231059 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231059 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000231059 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000231059 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000231059 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000231059 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000231059 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000231059 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000231059 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000231059 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000231059 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000231059 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000231059 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000231059 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000231059 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000231059 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006838 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006838 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006838 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006838 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006838 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006838 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006838 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006838 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006838 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006838 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006838 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006838 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006838 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006838 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006838 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006838 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006838 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006838 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006838 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006838 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006839 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006839 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006839 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006839 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006839 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006839 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006839 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006839 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006839 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006839 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006839 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006839 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006839 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006839 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006839 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006839 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006839 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006839 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006839 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006839 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006844 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006844 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006844 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006844 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006844 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006844 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006844 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006844 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006844 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006844 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006844 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006844 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006844 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006844 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006844 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006844 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006844 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006844 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006844 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006844 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006851 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006851 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006851 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006851 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006851 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006851 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006851 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006851 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006851 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006851 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006851 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006851 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006851 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006851 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006851 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006851 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006851 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006851 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006851 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006851 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006851 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006851 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006851 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006851 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006851 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006851 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006851 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006851 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006912 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006912 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006912 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006912 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006912 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006912 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006912 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006912 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006912 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006912 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006912 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006912 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006912 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006912 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006912 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006912 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006912 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006912 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006912 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006912 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006912 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006912 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006912 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006912 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006912 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006912 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006912 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006922 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006922 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006922 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006922 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006922 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006922 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006922 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006922 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006922 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006922 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006922 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006922 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006922 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006922 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006922 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006922 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006922 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006922 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006922 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006922 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006922 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006922 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006922 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006922 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006922 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006922 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006922 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006944 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006944 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006944 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006944 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000006944 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006944 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006944 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006944 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000006944 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006944 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006944 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006944 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006944 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006944 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006944 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006944 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000006944 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000006944 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000006944 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006944 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000006944 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000006944 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071425 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071425 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071425 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071425 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000071425 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000071425 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071425 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071425 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000071425 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071425 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071425 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000071425 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000071425 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071425 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000071425 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071425 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071425 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000071425 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000071425 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071425 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000071425 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000071425 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071427 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071427 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071427 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071427 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000071427 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000071427 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071427 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071427 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000071427 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071427 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071427 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000071427 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000071427 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071427 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000071427 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071427 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071427 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000071427 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000071427 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071427 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000071427 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000071427 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071435 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071435 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071435 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071435 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000071435 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071435 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000071435 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071435 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000071435 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071435 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071435 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000071435 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000071435 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000071435 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000071435 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071435 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000071435 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000071435 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000071435 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000071435 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000071435 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000071435 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000142778 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[11]
C000142778 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[11]
C000142778 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[11]
C000142778 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[11],[12]
C000142778 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[13]
C000142778 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[11]
C000142778 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[13]
C000142778 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[14]
C000142778 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[13]
C000142778 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[14]
C000142778 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[11]
C000142778 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[14]
C000142778 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[11],[15]
C000142778 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[11]
C000142778 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[14]
C000142778 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[14]
C000142778 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[14]
C000142778 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[14]
C000142780 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[16]
C000142780 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[16]
C000142780 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[16]
C000142780 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[16],[17]
C000142780 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[18]
C000142780 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[16]
C000142780 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[18]
C000142780 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[19]
C000142780 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[18]
C000142780 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[19]
C000142780 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[16]
C000142780 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[19]
C000142780 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[16],[20]
C000142780 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[16]
C000142780 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[19]
C000142780 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[19]
C000142780 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[19]
C000142780 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[19]
C000160039 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160039 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160039 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160039 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160039 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160039 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160039 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160039 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160039 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160039 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160039 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160039 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160039 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160039 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160039 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160039 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160039 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160039 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160039 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160039 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160039 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160039 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160039 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160041 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160041 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160041 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160041 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160041 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160041 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160041 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160041 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160041 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160041 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160041 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160041 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160041 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160041 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160041 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160041 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160041 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160041 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160041 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160041 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160041 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160041 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160041 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172716 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172716 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172716 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172716 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172716 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172716 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172716 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172716 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172716 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172716 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172716 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172716 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172716 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172716 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172716 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172716 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172716 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000172718 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172718 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172718 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172718 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172718 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172718 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172718 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172718 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172718 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172718 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172718 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172718 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172718 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172718 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172718 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172718 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172718 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172718 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000006858 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006858 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006858 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006858 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006858 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006858 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006858 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006858 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006858 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006858 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006858 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006858 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006858 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006858 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006858 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006858 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006858 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006858 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006858 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006858 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006858 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006858 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006858 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006858 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006858 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006858 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006858 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006858 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006862 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006862 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006862 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006862 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006862 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006862 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006862 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006862 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006862 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006862 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006862 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006862 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006862 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006862 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006862 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006862 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006862 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006862 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006862 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006862 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006862 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006862 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006862 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006862 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006862 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006862 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006862 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006862 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006906 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.70%
C000006906 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006906 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006906 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000006906 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000006906 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006906 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006906 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000006906 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006906 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006906 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006906 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000006906 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006906 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006906 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006906 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006906 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006906 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000006906 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006906 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000006906 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000006906 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006929 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006929 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006929 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006929 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006929 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006929 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006929 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006929 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006929 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006929 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006931 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006931 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006931 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006931 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006931 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006931 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006931 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006931 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006931 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006931 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006941 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006941 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006941 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006941 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000006941 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006941 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006941 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006941 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000006941 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006941 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006941 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006941 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006941 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006941 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006941 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006941 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000006941 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000006941 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000006941 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006941 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000006941 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000006941 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006943 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006943 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006943 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006943 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000006943 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006943 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006943 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000006943 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000006943 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006943 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006943 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006943 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006943 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006943 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006943 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006943 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000006943 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000006943 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000006943 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006943 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000006943 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000006943 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071424 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071424 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071424 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071424 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000071424 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000071424 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071424 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071424 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000071424 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071424 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071424 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000071424 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000071424 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071424 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000071424 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071424 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071424 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000071424 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000071424 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071424 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000071424 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000071424 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000142781 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[21]
C000142781 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[21]
C000142781 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[21]
C000142781 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[21],[22]
C000142781 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[23]
C000142781 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[21]
C000142781 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[23]
C000142781 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[24]
C000142781 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[23]
C000142781 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[24]
C000142781 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[21]
C000142781 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[24]
C000142781 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[21],[25]
C000142781 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[21]
C000142781 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[24]
C000142781 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[24]
C000142781 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[24]
C000142781 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[24]
C000160034 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160034 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160034 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160034 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160034 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160034 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160034 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160034 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160034 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160034 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160034 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160034 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160034 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160034 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160034 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160034 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160034 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160034 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160034 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160034 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160034 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160034 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160034 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160036 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160036 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160036 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160036 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160036 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160036 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160036 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160036 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160036 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160036 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160036 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160036 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160036 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160036 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160036 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160036 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160036 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160036 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160036 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160036 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160036 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160036 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160036 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000172719 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172719 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172719 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172719 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172719 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172719 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172719 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172719 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172719 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172719 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172719 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172719 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172719 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172719 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172719 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172719 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172719 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172719 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000172721 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172721 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172721 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172721 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172721 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172721 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172721 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172721 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172721 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172721 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172721 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172721 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172721 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172721 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172721 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172721 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172721 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172721 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000195688 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[26]
C000195688 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[26]
C000195688 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[26]
C000195688 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[26],[27]
C000195688 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[28]
C000195688 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[26]
C000195688 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[28]
C000195688 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[29]
C000195688 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[28]
C000195688 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[29]
C000195688 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[26]
C000195688 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[29]
C000195688 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[26],[30]
C000195688 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[26]
C000195688 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[29]
C000195688 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[29]
C000195688 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[29]
C000195688 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[29]
C000006847 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006847 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006847 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006847 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006847 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006847 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006847 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006847 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006847 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006847 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006847 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006847 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006847 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006847 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006847 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006847 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006847 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006847 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006847 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006847 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006849 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006849 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006849 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006849 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006849 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006849 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006849 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006849 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006849 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006849 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006849 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006849 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006849 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006849 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006849 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006849 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006849 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006849 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006849 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006849 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006896 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006896 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006896 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006896 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006896 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006896 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006896 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006896 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006896 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006896 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006896 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006896 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006896 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006896 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006896 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006896 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006896 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006896 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006896 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006896 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006896 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006896 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006896 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006896 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006896 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006896 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006896 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006898 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006898 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006898 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006898 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006898 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006898 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006898 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006898 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006898 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006898 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006898 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006898 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006898 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006898 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006898 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006898 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006898 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006898 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006898 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006898 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006898 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006898 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006898 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006898 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006898 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006898 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006898 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006911 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006911 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006911 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006911 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006911 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006911 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006911 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006911 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006911 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006911 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006911 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006911 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006911 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006911 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006911 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006911 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006911 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006911 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006911 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006911 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006911 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006911 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006911 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006911 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006911 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006911 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006911 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006916 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006916 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006916 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006916 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006916 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006916 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006916 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006916 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006916 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006916 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006916 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006916 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006916 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006916 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006916 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006916 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006916 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006916 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006916 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006916 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006916 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006916 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006916 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006916 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006916 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006916 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006916 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006920 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000006920 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006920 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006920 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000006920 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006920 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000006920 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006920 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006920 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006920 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006920 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006920 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000006920 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006920 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000006920 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006920 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006920 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000006920 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006920 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000006920 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006920 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006920 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006920 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006920 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000006920 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006920 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000006920 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006937 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006937 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006937 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006937 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006937 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006937 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000006937 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006937 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006937 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006937 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006937 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000006937 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000006937 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000006937 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000006937 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000006937 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006937 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000006937 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000006937 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006937 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006937 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000006937 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006938 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006938 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006938 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006938 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006938 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006938 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000006938 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006938 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006938 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006938 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006938 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000006938 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000006938 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000006938 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000006938 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000006938 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006938 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000006938 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000006938 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006938 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006938 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000006938 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000142775 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[31]
C000142775 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[31]
C000142775 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[31]
C000142775 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[31],[32]
C000142775 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[33]
C000142775 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[31]
C000142775 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[33]
C000142775 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[34]
C000142775 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[33]
C000142775 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[34]
C000142775 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[31]
C000142775 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[34]
C000142775 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[31],[35]
C000142775 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[31]
C000142775 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[34]
C000142775 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[34]
C000142775 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[34]
C000142775 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[34]
C000142776 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[36]
C000142776 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[36]
C000142776 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[36]
C000142776 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[36],[37]
C000142776 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[38]
C000142776 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[36]
C000142776 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[38]
C000142776 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[39]
C000142776 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[38]
C000142776 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[39]
C000142776 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[36]
C000142776 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[39]
C000142776 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[36],[40]
C000142776 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[36]
C000142776 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[39]
C000142776 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[39]
C000142776 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[39]
C000142776 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[39]
C000160026 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160026 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160026 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160026 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160026 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160026 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160026 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160026 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160026 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160026 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160026 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160026 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160026 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160026 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160026 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160026 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160026 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160026 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160026 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160026 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160026 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160026 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160026 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160029 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160029 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160029 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160029 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160029 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160029 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160029 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160029 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160029 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160029 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160029 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160029 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160029 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160029 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160029 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160029 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160029 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160029 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160029 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160029 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160029 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160029 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160029 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160043 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160043 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160043 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160043 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160043 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160043 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160043 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160043 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160043 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160043 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160043 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160043 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160043 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160043 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160043 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160043 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160043 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160043 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160043 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160043 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160043 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160043 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160043 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160044 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160044 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160044 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160044 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160044 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160044 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160044 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160044 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160044 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160044 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160044 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160044 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160044 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160044 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160044 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160044 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160044 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160044 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160044 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160044 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160044 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160044 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160044 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000220107 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220107 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220107 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220107 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220107 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220107 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220107 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220107 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220107 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220107 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220107 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220107 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220107 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220107 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220107 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220107 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220107 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220107 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220107 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220107 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220107 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220107 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220108 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220108 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220108 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220108 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220108 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220108 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220108 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220108 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220108 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220108 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220108 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220108 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220108 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220108 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220108 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220108 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220108 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220108 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220108 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220108 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220108 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220108 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000006843 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000006843 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006843 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006843 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006843 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006843 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006843 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000006843 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000006843 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000006843 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000006843 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006843 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006843 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000006843 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006843 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006843 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000006843 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000006843 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006843 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000006843 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000006892 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006892 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006892 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006892 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006892 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006892 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006892 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006892 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006892 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006892 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006892 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006892 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006892 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006892 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006892 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006892 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006892 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006892 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006892 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006892 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006892 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006892 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006892 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006892 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006892 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006892 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006892 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006936 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006936 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006936 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006936 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006936 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006936 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006936 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006936 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006936 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006936 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000071426 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071426 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071426 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071426 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000071426 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000071426 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071426 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000071426 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000071426 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071426 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000071426 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000071426 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000071426 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071426 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000071426 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071426 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000071426 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000071426 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000071426 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071426 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000071426 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000071426 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000071431 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071431 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071431 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071431 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000071431 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071431 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000071431 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071431 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071431 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071431 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071431 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000071431 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000071431 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000071431 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000071431 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000071431 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071431 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000071431 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000071431 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000071431 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071431 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000071431 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000071436 [Member] | Franco Nevada Corp [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071436 [Member] | AIB Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071436 [Member] | CaixaBank S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071436 [Member] | Cadence Design Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000071436 [Member] | Resona Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000071436 [Member] | TotalEnergies SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000071436 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000071436 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.40%
C000071436 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	2.80%
C000071436 [Member] | Legrand S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071436 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000071436 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	7.10%
C000071436 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	4.90%
C000071436 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	10.10%
C000071436 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071436 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	14%
C000071436 [Member] | SPAIN
Holdings [Line Items]
Percent of Total Investments	4.30%
C000071436 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17.40%
C000071436 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	9.20%
C000071436 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	13.90%
C000071436 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.10%
C000071436 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000142779 [Member]
Holdings [Line Items]
Percent of Net Asset Value	100%	[41]
C000142779 [Member] | Downside Hedge [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[41]
C000142779 [Member] | Limited Maturity U S Treasury Notes [Member]
Holdings [Line Items]
Percent of Net Asset Value	3%	[41]
C000142779 [Member] | Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.90%	[41],[42]
C000142779 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[43]
C000142779 [Member] | Net Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	31.30%	[41]
C000142779 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.20%	[43]
C000142779 [Member] | Standard And Poors 500 Index Option 4200 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.30%)	[44]
C000142779 [Member] | MFS Institutional International Equity Fund [Member]
Holdings [Line Items]
Percent of Net Asset Value	30.40%	[43]
C000142779 [Member] | Mini Russell 1000 Value Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.30%)	[44]
C000142779 [Member] | Net Equivalent Equity Exposure [Member]
Holdings [Line Items]
Percent of Net Asset Value	29.80%	[41]
C000142779 [Member] | Standard And Poors 500 Index Option 4200 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.20%)	[44]
C000142779 [Member] | Other [Member]
Holdings [Line Items]
Percent of Net Asset Value	61.30%	[41],[45]
C000142779 [Member] | Standard And Poors Index Option PUT [Member]
Holdings [Line Items]
Percent of Net Asset Value	(1.50%)	[41]
C000142779 [Member] | Mini Russell 1000 Growth Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(20.70%)	[44]
C000142779 [Member] | Standard And Poors 500 Index Option 4700 00 PUT SEP 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[44]
C000142779 [Member] | Mini MSCI EAFE Index Future JUN 21 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(19.70%)	[44]
C000142779 [Member] | Standard And Poors 500 Index Option 4400 00 PUT DEC 20 24 [Member]
Holdings [Line Items]
Percent of Net Asset Value	(0.50%)	[44]
C000160022 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160022 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160022 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160022 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160022 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160022 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160022 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160022 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160022 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160022 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160022 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160022 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160022 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160022 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160022 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160022 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160022 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160022 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160022 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160022 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160022 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160022 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160022 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160033 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160033 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160033 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160033 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160033 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160033 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160033 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160033 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160033 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160033 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160033 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160033 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160033 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160033 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160033 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160033 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160033 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160033 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160033 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160033 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160033 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160033 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160033 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160040 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160040 [Member] | Eaton Corp PLC [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160040 [Member] | Johnson And Johnson [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000160040 [Member] | American Express Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160040 [Member] | Cigna Group [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160040 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160040 [Member] | Berkshire Hathaway Inc B [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160040 [Member] | Pfizer Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000160040 [Member] | JPMorgan Chase And Co [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160040 [Member] | Wells Fargo And Co [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000160040 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160040 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000160040 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	22.80%
C000160040 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000160040 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160040 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000160040 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.30%
C000160040 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%
C000160040 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000160040 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000160040 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000160040 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.50%
C000160040 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172715 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172715 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172715 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172715 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172715 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172715 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172715 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172715 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172715 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172715 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172715 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172715 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172715 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172715 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172715 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172715 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172715 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000220111 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220111 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220111 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220111 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220111 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220111 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220111 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220111 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220111 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220111 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220111 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220111 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220111 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220111 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220111 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220111 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220111 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220111 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220111 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220111 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220111 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220111 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000231058 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	30.20%
C000231058 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231058 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000231058 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000231058 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000231058 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000231058 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%
C000231058 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000231058 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000231058 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000231058 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000231058 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000231058 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.80%
C000231058 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000231058 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000231058 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000231058 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000231058 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231058 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	58.50%
C000231058 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000231060 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000231060 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000231060 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000231060 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231060 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231060 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231060 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231060 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231060 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000231060 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231060 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000231060 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000231060 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000231060 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231060 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000231060 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000231060 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231060 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000231060 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000231060 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000231060 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000231060 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000231060 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000231060 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000231060 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000231060 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000231060 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231061 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	20.20%
C000231061 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231061 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231061 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	19%
C000231061 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231061 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000231061 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000231061 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000231061 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000231061 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231061 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231061 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000231061 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000231061 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.10%
C000231061 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000231061 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000231061 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000231061 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000231061 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.80%
C000231061 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231061 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000231061 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%
C000231061 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231061 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000231061 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000231061 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	50.70%
C000231061 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006852 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006852 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006852 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4.90%
C000006852 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	38.20%
C000006852 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006852 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006852 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006852 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006852 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006852 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006852 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006852 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006852 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006852 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.10%
C000006852 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7.30%
C000006852 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.30%
C000006852 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006852 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006852 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006852 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006852 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%
C000006852 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	8.10%
C000006852 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006852 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000006852 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006852 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	39.70%
C000006852 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.20%
C000006852 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006887 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006887 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006887 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006887 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006887 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006887 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006887 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006887 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006887 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006887 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006887 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006887 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006887 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006887 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006887 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006887 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006887 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006887 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006887 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006887 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006887 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006887 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006887 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006887 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006887 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006887 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006887 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006888 [Member] | International Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	8%
C000006888 [Member] | MFS Global Opportunistic Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000006888 [Member] | Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	58.60%
C000006888 [Member] | MFS Commodity Strategy Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006888 [Member] | MFS Emerging Markets Debt Local Currency Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006888 [Member] | MFS Global Real Estate Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006888 [Member] | MFS High Income Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006888 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006888 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006888 [Member] | MFS Emerging Markets Debt Fund [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000006888 [Member] | MFS Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%
C000006888 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006888 [Member] | MFS Limited Maturity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006888 [Member] | MFS Mid Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006888 [Member] | MFS Research Fund [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000006888 [Member] | MFS Total Return Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	14.40%
C000006888 [Member] | Non Traditional Funds [Member]
Holdings [Line Items]
Percent of Total Investments	4%
C000006888 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000006888 [Member] | MFS Mid Cap Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006888 [Member] | MFS New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006888 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000006888 [Member] | MFS Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	6%
C000006888 [Member] | MFS New Discovery Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	1%
C000006888 [Member] | MFS Inflation Adjusted Bond Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.90%
C000006888 [Member] | U S Stock Funds [Member]
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006888 [Member] | MFS Government Securities Fund [Member]
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006888 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006904 [Member] | HDFC Bank Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006904 [Member] | China Construction Bank Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006904 [Member] | Alibaba Group Holding Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006904 [Member] | Samsung Electronics Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%
C000006904 [Member] | Tencent Holdings Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	5.70%
C000006904 [Member] | Vale S A ADR [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006904 [Member] | Hon Hai Precision Industry Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000006904 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000006904 [Member] | Infosys Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000006904 [Member] | Tata Consultancy Services Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000006904 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%
C000006904 [Member] | INDIA
Holdings [Line Items]
Percent of Total Investments	14.50%
C000006904 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006904 [Member] | CHINA
Holdings [Line Items]
Percent of Total Investments	26.40%
C000006904 [Member] | HONG KONG
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006904 [Member] | INDONESIA
Holdings [Line Items]
Percent of Total Investments	2.90%
C000006904 [Member] | BRAZIL
Holdings [Line Items]
Percent of Total Investments	6.90%
C000006904 [Member] | KOREA, REPUBLIC OF
Holdings [Line Items]
Percent of Total Investments	14.80%
C000006904 [Member] | MEXICO
Holdings [Line Items]
Percent of Total Investments	2.80%
C000006904 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	14.10%
C000006904 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	97.90%
C000006904 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000006925 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006925 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006925 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006925 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006925 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006925 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006925 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006925 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006925 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006925 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006935 [Member] | MFS Emerging Markets Equity Fund [Member]
Holdings [Line Items]
Percent of Total Investments	17.10%
C000006935 [Member] | International Stock Funds Portfolio actual allocation [Member]
Holdings [Line Items]
Percent of Total Investments	99.90%
C000006935 [Member] | MFS Institutional Money Market Portfolio [Member]
Holdings [Line Items]
Percent of Total Investments	0.10%
C000006935 [Member] | MFS International Growth Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006935 [Member] | MFS International Intrinsic Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15%
C000006935 [Member] | MFS International Large Cap Value Fund [Member]
Holdings [Line Items]
Percent of Total Investments	15.10%
C000006935 [Member] | MFS Research International Fund [Member]
Holdings [Line Items]
Percent of Total Investments	27.70%
C000006935 [Member] | International Stock Funds Portfolio target allocation [Member]
Holdings [Line Items]
Percent of Total Investments	100%
C000006935 [Member] | MFS International New Discovery Fund [Member]
Holdings [Line Items]
Percent of Total Investments	10%
C000006935 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.10%
C000006940 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006940 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000006940 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000006940 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000006940 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000006940 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000006940 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006940 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000006940 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000006940 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000006940 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000006940 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000006940 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000006940 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000006940 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000006940 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006940 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000006940 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000006940 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000006940 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000006940 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000006940 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000071430 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071430 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071430 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071430 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000071430 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071430 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000071430 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071430 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071430 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071430 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071430 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000071430 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000071430 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000071430 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000071430 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000071430 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071430 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000071430 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000071430 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000071430 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071430 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000071430 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000071432 [Member] | Heineken N V [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071432 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000071432 [Member] | Amadeus IT Group S A [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000071432 [Member] | Nestle S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.90%
C000071432 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	3%
C000071432 [Member] | Hitachi Ltd [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%
C000071432 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071432 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member]
Holdings [Line Items]
Percent of Total Investments	4.70%
C000071432 [Member] | SAP SE [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000071432 [Member] | Linde PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.60%
C000071432 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	23.10%
C000071432 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	10.20%
C000071432 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	4%
C000071432 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	6.50%
C000071432 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	8.20%
C000071432 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071432 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	17%
C000071432 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	10.50%
C000071432 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	9.30%
C000071432 [Member] | TAIWAN
Holdings [Line Items]
Percent of Total Investments	5.60%
C000071432 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.60%
C000071432 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160021 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160021 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160021 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160021 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160021 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160021 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160021 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160021 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160021 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160021 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160021 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160021 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160021 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160021 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160021 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160021 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160021 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160021 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160021 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160021 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160021 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160021 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160021 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160023 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160023 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160023 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160023 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160023 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160023 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160023 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160023 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160023 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160023 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160023 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160023 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160023 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160023 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160023 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160023 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160023 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160023 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160023 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160023 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160023 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160023 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160023 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160025 [Member] | Meta Platforms Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	4.80%
C000160025 [Member] | Apple Inc [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%
C000160025 [Member] | Applied Materials Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160025 [Member] | Alphabet Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160025 [Member] | Alphabet Inc C [Member]
Holdings [Line Items]
Percent of Total Investments	3.60%
C000160025 [Member] | Booking Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160025 [Member] | NVIDIA Corp [Member]
Holdings [Line Items]
Percent of Total Investments	11.10%
C000160025 [Member] | Microsoft Corp [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160025 [Member] | Amazon com Inc [Member]
Holdings [Line Items]
Percent of Total Investments	6.90%
C000160025 [Member] | Eli Lilly And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160025 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%
C000160025 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000160025 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	6.40%
C000160025 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%
C000160025 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	44%
C000160025 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.90%
C000160025 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	13.40%
C000160025 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.30%
C000160025 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000160025 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.50%
C000160025 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	0.40%
C000160025 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.40%
C000160025 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.60%
C000160030 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160030 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160030 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160030 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160030 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160030 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160030 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160030 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160030 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160030 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160030 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160030 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160030 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160030 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160030 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160030 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160030 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160030 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160030 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160030 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160030 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160030 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160030 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000160032 [Member] | Encompass Health Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160032 [Member] | e l f Beauty Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.60%
C000160032 [Member] | Grand Canyon Education Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.70%
C000160032 [Member] | Skechers USA Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000160032 [Member] | Verint Systems Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160032 [Member] | Prestige Consumer Healthcare Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160032 [Member] | SLM Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160032 [Member] | APi Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160032 [Member] | Organon And Co [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160032 [Member] | TaskUs Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000160032 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.90%
C000160032 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160032 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160032 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	1.40%
C000160032 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	14%
C000160032 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7%
C000160032 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.80%
C000160032 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.20%
C000160032 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2.30%
C000160032 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	16.30%
C000160032 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000160032 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	99.30%
C000160032 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	0.70%
C000172723 [Member] | Equitable Holdings Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Ameriprise Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172723 [Member] | Hartford Financial Services Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%
C000172723 [Member] | McKesson Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Corebridge Financial Inc [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Wabtec Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Phillips 66 [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172723 [Member] | Vistra Corp [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Spotify Technology S A [Member]
Holdings [Line Items]
Percent of Total Investments	1.90%
C000172723 [Member] | Verisk Analytics Inc A [Member]
Holdings [Line Items]
Percent of Total Investments	1.50%
C000172723 [Member] | Communications Sector [Member]
Holdings [Line Items]
Percent of Total Investments	4.10%
C000172723 [Member] | Real Estate Sector [Member]
Holdings [Line Items]
Percent of Total Investments	7.90%
C000172723 [Member] | Financials [Member]
Holdings [Line Items]
Percent of Total Investments	17.30%
C000172723 [Member] | Utilities Sector [Member]
Holdings [Line Items]
Percent of Total Investments	6.80%
C000172723 [Member] | Information Technology Sector [Member]
Holdings [Line Items]
Percent of Total Investments	12%
C000172723 [Member] | Energy Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5.20%
C000172723 [Member] | Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Total Investments	9.40%
C000172723 [Member] | Healthcare Sector [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%
C000172723 [Member] | Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000172723 [Member] | Industrial Sector [Member]
Holdings [Line Items]
Percent of Total Investments	18.50%
C000172723 [Member] | Materials Sector [Member]
Holdings [Line Items]
Percent of Total Investments	5%
C000172723 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	98.70%
C000172723 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%
C000220112 [Member] | Glencore PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.20%
C000220112 [Member] | Henkel AG And Co KGaA [Member]
Holdings [Line Items]
Percent of Total Investments	2%
C000220112 [Member] | Eni S p A [Member]
Holdings [Line Items]
Percent of Total Investments	2.70%
C000220112 [Member] | BNP Paribas S A [Member]
Holdings [Line Items]
Percent of Total Investments	3.30%
C000220112 [Member] | UBS Group AG [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
C000220112 [Member] | Roche Holding AG [Member]
Holdings [Line Items]
Percent of Total Investments	2.40%
C000220112 [Member] | NatWest Group PLC [Member]
Holdings [Line Items]
Percent of Total Investments	3.10%
C000220112 [Member] | Schneider Electric SE [Member]
Holdings [Line Items]
Percent of Total Investments	2.50%
C000220112 [Member] | Willis Towers Watson PLC [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%
C000220112 [Member] | Mitsubishi UFJ Financial Group Inc [Member]
Holdings [Line Items]
Percent of Total Investments	3.50%
C000220112 [Member] | Other Countries [Member]
Holdings [Line Items]
Percent of Total Investments	11.50%
C000220112 [Member] | SWITZERLAND
Holdings [Line Items]
Percent of Total Investments	9%
C000220112 [Member] | IRELAND
Holdings [Line Items]
Percent of Total Investments	3.90%
C000220112 [Member] | UNITED STATES
Holdings [Line Items]
Percent of Total Investments	6.20%
C000220112 [Member] | CANADA
Holdings [Line Items]
Percent of Total Investments	5.80%
C000220112 [Member] | UNITED KINGDOM
Holdings [Line Items]
Percent of Total Investments	23.90%
C000220112 [Member] | NETHERLANDS
Holdings [Line Items]
Percent of Total Investments	2.80%
C000220112 [Member] | FRANCE
Holdings [Line Items]
Percent of Total Investments	15.10%
C000220112 [Member] | GERMANY
Holdings [Line Items]
Percent of Total Investments	5.60%
C000220112 [Member] | JAPAN
Holdings [Line Items]
Percent of Total Investments	16.20%
C000220112 [Member] | Equities [Member]
Holdings [Line Items]
Percent of Total Investments	96.80%
C000220112 [Member] | Money Market Funds [Member]
Holdings [Line Items]
Percent of Total Investments	3.20%
[1]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[2]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[3]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[4]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[5]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[6]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[7]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[8]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[9]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[10]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[11]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[12]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[13]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[14]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[15]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[16]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[17]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[18]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[19]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[20]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[21]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[22]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[23]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[24]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[25]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[26]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[27]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[28]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[29]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[30]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[31]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[32]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[33]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[34]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[35]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[36]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[37]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[38]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[39]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[40]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[41]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[42]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[43]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[44]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[45]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.