| Form N-CSR Cover | 12 Months Ended |
| Oct. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | MFS SERIES TRUST VIII |
| Entity Central Index Key | 0000819673 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Oct. 31, 2024 |
| Shareholder Report | 12 Months Ended | |
| Oct. 31, 2024 USD ($) Holding | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSR | |
| Amendment Flag | false | |
| Registrant Name | MFS SERIES TRUST VIII | |
| Entity Central Index Key | 0000819673 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Oct. 31, 2024 | |
| C000006697 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class A | |
| Trading Symbol | MWOFX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.22 % | |
| Expenses Paid, Amount | $ 138 | |
| Expense Ratio, Percent | 1.22% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class A shares of the MFS Global Growth Fund (fund) provided a total return of 26.10%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 26.10 % 10.41 % 10.51 % A with initial sales charge (5.75%) 18.85 % 9.11 % 9.86 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/a | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [1] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006699 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class B | |
| Trading Symbol | MWOBX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.97 % | |
| Expenses Paid, Amount | $ 222 | |
| Expense Ratio, Percent | 1.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class B shares of the MFS Global Growth Fund (fund) provided a total return of 25.17%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 25.17 % 9.59 % 9.68 % B with CDSC (declining over six years from 4% to 0%) × 21.17 % 9.31 % 9.68 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. | |
| 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/b | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [2] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006700 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class C | |
| Trading Symbol | MWOCX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.97 % | |
| Expenses Paid, Amount | $ 222 | |
| Expense Ratio, Percent | 1.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class C shares of the MFS Global Growth Fund (fund) provided a total return of 25.17%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 25.17 % 9.59 % 9.68 % C with CDSC (1% for 12 months) × 24.17 % 9.59 % 9.68 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. | |
| 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/c | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [3] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006701 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class I | |
| Trading Symbol | MWOIX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 0.97 % | |
| Expenses Paid, Amount | $ 110 | |
| Expense Ratio, Percent | 0.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class I shares of the MFS Global Growth Fund (fund) provided a total return of 26.43%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 26.43 % 10.69 % 10.78 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/i | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [4] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006703 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class R1 | |
| Trading Symbol | MWOGX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.97 % | |
| Expenses Paid, Amount | $ 222 | |
| Expense Ratio, Percent | 1.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R1 shares of the MFS Global Growth Fund (fund) provided a total return of 25.14%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 25.14 % 9.59 % 9.68 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r1 | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [5] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006705 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class R2 | |
| Trading Symbol | MGWRX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.47 % | |
| Expenses Paid, Amount | $ 166 | |
| Expense Ratio, Percent | 1.47% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R2 shares of the MFS Global Growth Fund (fund) provided a total return of 25.79%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 25.79 % 10.14 % 10.23 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r2 | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [6] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006706 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class R3 | |
| Trading Symbol | MWOHX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 1.22 % | |
| Expenses Paid, Amount | $ 138 | |
| Expense Ratio, Percent | 1.22% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R3 shares of the MFS Global Growth Fund (fund) provided a total return of 26.11%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 26.11 % 10.41 % 10.50 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r3 | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [7] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006698 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class R4 | |
| Trading Symbol | MWOJX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 0.97 % | |
| Expenses Paid, Amount | $ 110 | |
| Expense Ratio, Percent | 0.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R4 shares of the MFS Global Growth Fund (fund) provided a total return of 26.42%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 26.42 % 10.69 % 10.78 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r4 | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [8] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000126358 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Fund | |
| Class Name | Class R6 | |
| Trading Symbol | MWOKX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Fund for the period of November 1, 2023 to October 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 $ 0.89 % | |
| Expenses Paid, Amount | $ 101 | |
| Expense Ratio, Percent | 0.89% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R6 shares of the MFS Global Growth Fund (fund) provided a total return of 26.53%, at net asset value. This compares with a return of 32.79% for the fund’s benchmark, the MSCI All Country World Index (net div). The fund's other benchmark, the MSCI All Country World Growth Index (net div), generated a return of 37.22%. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the MSCI All Country World Index: The fund's avoidance of the weak-performing energy sector benefited relative returns. The combination of an underweight allocation and security selection within the materials sector further supported relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within the consumer discretionary, consumer staples, and communication services sectors held back relative performance. | |
| 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 10/31/24 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 26.53 % 10.78 % 10.87 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 32.79 % 11.08 % 9.06 % MSCI All Country World Growth Index (net div) +∆ 37.22 % 13.51 % 11.42 % + Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. ∆ 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 March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r6 | |
| Net Assets | $ 963,333,923 | |
| Holdings Count | Holding | 72 | |
| Advisory Fees Paid, Amount | $ 8,419,821 | [9] |
| Investment Company Portfolio Turnover | 23% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 963,333,923 Total Management Fee ($)#: 8,419,821 Total Number of Holdings: 72 Portfolio Turnover Rate (%): 23 # 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 10/31/24) Portfolio structure Equities 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % Issuer country weightings United States 70.4 % Canada 5.4 % France 4.4 % Taiwan 4.1 % China 3.6 % Japan 2.3 % India 2.2 % Switzerland 1.9 % South Korea 1.3 % Other Countries 4.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 5.3 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 4.1 % Visa, Inc., "A" 3.7 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.8 % Alphabet, Inc., "A" 2.8 % Apple, Inc. 2.7 % Tencent Holdings Ltd. 2.2 % HDFC Bank Ltd. 2.2 % Canadian Pacific Kansas City Ltd. 2.1 % | |
| C000006707 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Fund | |
| Class Name | Class A | |
| Trading Symbol | MFIOX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Fund for the period of November 1, 2023 to October 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 $ 0.73 % | |
| Expenses Paid, Amount | $ 77 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class A shares of the MFS Income Fund (fund) provided a total return of 12.23%, at net asset value. This compares with a return of 10.55% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund’s asset allocation decisions, most notably, its holdings of collateralized mortgage obligation (CMO) securities, for which the benchmark has no exposure, coupled with its overweight allocation to both the industrials and financial institutions sectors, contributed to performance. From a quality perspective, the fund’s out-of-benchmark exposure to “BB” and “B” -rated securities benefited relative returns, as bonds within these credit quality segments outperformed the benchmark during the reporting period. Bond selection within both the industrials and financial institutions sectors, particularly within “BBB” and “A” -rated bonds, also supported relative returns. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: Conversely, the fund's duration positioning, particularly along the short end (centered around maturities of less than 5 years) of the yield curve, detracted from relative performance as interest rates generally declined over the reporting period. | |
| 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 10/31/24 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 12.23 % 0.93 % ) 2.32 % A with initial sales charge (4.25%) 7.46 % 0.06 % ) 1.87 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 10.55 % (0.23 ) % 1.49 % ∆ 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. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/a | |
| Net Assets | $ 5,670,398,296 | |
| Holdings Count | Holding | 486 | |
| Advisory Fees Paid, Amount | $ 17,041,863 | [10] |
| Investment Company Portfolio Turnover | 50% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 5,670,398,296 Average Effective Maturity (yrs): 9.1 Total Number of Holdings: 486 Average Effective Duration (yrs): 6.1 Total Management Fee ($)#: 17,041,863 Portfolio Turnover Rate (%): 50 # 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 10/31/24) Portfolio structure at value Fixed Income 98.7 % Money Market Funds 1.3 % Composition including fixed income credit quality AAA 7.6 % AA 6.1 % A 12.5 % BBB 26.7 % BB 6.1 % B 5.1 % CCC 0.8 % C 0.0 % U.S. Government 32.1 % Federal Agencies 1.6 % Not Rated 0.1 % Money Market Funds 1.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since November 1, 2023. For more complete information, you may review the fund's next prospectus, which we expect to be available on February 28, 2025 at Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | funds.mfs.com | |
| C000006708 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Fund | |
| Class Name | Class B | |
| Trading Symbol | MIOBX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Fund for the period of November 1, 2023 to October 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 $ 1.48 % | |
| Expenses Paid, Amount | $ 157 | |
| Expense Ratio, Percent | 1.48% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class B shares of the MFS Income Fund (fund) provided a total return of 11.64%, at net asset value. This compares with a return of 10.55% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund’s asset allocation decisions, most notably, its holdings of collateralized mortgage obligation (CMO) securities, for which the benchmark has no exposure, coupled with its overweight allocation to both the industrials and financial institutions sectors, contributed to performance. From a quality perspective, the fund’s out-of-benchmark exposure to “BB” and “B” -rated securities benefited relative returns, as bonds within these credit quality segments outperformed the benchmark during the reporting period. Bond selection within both the industrials and financial institutions sectors, particularly within “BBB” and “A” -rated bonds, also supported relative returns. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: Conversely, the fund's duration positioning, particularly along the short end (centered around maturities of less than 5 years) of the yield curve, detracted from relative performance as interest rates generally declined over the reporting period. | |
| 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 10/31/24 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 11.64 % 0.20 % ) 1.59 % B with CDSC (declining over six years from 4% to 0%) × 7.64 % (0.15 ) % 1.59 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 10.55 % (0.23 ) % 1.49 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. | |
| 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. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/b | |
| Net Assets | $ 5,670,398,296 | |
| Holdings Count | Holding | 486 | |
| Advisory Fees Paid, Amount | $ 17,041,863 | [11] |
| Investment Company Portfolio Turnover | 50% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 5,670,398,296 Average Effective Maturity (yrs): 9.1 Total Number of Holdings: 486 Average Effective Duration (yrs): 6.1 Total Management Fee ($)#: 17,041,863 Portfolio Turnover Rate (%): 50 # 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 10/31/24) Portfolio structure at value Fixed Income 98.7 % Money Market Funds 1.3 % Composition including fixed income credit quality AAA 7.6 % AA 6.1 % A 12.5 % BBB 26.7 % BB 6.1 % B 5.1 % CCC 0.8 % C 0.0 % U.S. Government 32.1 % Federal Agencies 1.6 % Not Rated 0.1 % Money Market Funds 1.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since November 1, 2023. For more complete information, you may review the fund's next prospectus, which we expect to be available on February 28, 2025 at Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | funds.mfs.com | |
| C000006709 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Fund | |
| Class Name | Class C | |
| Trading Symbol | MIOCX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Fund for the period of November 1, 2023 to October 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 $ 1.48 % | |
| Expenses Paid, Amount | $ 156 | |
| Expense Ratio, Percent | 1.48% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class C shares of the MFS Income Fund (fund) provided a total return of 11.47%, at net asset value. This compares with a return of 10.55% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund’s asset allocation decisions, most notably, its holdings of collateralized mortgage obligation (CMO) securities, for which the benchmark has no exposure, coupled with its overweight allocation to both the industrials and financial institutions sectors, contributed to performance. From a quality perspective, the fund’s out-of-benchmark exposure to “BB” and “B” -rated securities benefited relative returns, as bonds within these credit quality segments outperformed the benchmark during the reporting period. Bond selection within both the industrials and financial institutions sectors, particularly within “BBB” and “A” -rated bonds, also supported relative returns. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: Conversely, the fund's duration positioning, particularly along the short end (centered around maturities of less than 5 years) of the yield curve, detracted from relative performance as interest rates generally declined over the reporting period. | |
| 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 10/31/24 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 11.47 % 0.19 % ) 1.58 % C with CDSC (1% for 12 months) × 10.47 % 0.19 % ) 1.58 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 10.55 % (0.23 ) % 1.49 % ∆ Source: FactSet Research Systems Inc. × Assuming redemption at the end of the applicable period. | |
| 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. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/c | |
| Net Assets | $ 5,670,398,296 | |
| Holdings Count | Holding | 486 | |
| Advisory Fees Paid, Amount | $ 17,041,863 | [12] |
| Investment Company Portfolio Turnover | 50% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 5,670,398,296 Average Effective Maturity (yrs): 9.1 Total Number of Holdings: 486 Average Effective Duration (yrs): 6.1 Total Management Fee ($)#: 17,041,863 Portfolio Turnover Rate (%): 50 # 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 10/31/24) Portfolio structure at value Fixed Income 98.7 % Money Market Funds 1.3 % Composition including fixed income credit quality AAA 7.6 % AA 6.1 % A 12.5 % BBB 26.7 % BB 6.1 % B 5.1 % CCC 0.8 % C 0.0 % U.S. Government 32.1 % Federal Agencies 1.6 % Not Rated 0.1 % Money Market Funds 1.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since November 1, 2023. For more complete information, you may review the fund's next prospectus, which we expect to be available on February 28, 2025 at Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | funds.mfs.com | |
| C000006710 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Fund | |
| Class Name | Class I | |
| Trading Symbol | MFIIX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Fund for the period of November 1, 2023 to October 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 $ 0.48 % | |
| Expenses Paid, Amount | $ 51 | |
| Expense Ratio, Percent | 0.48% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class I shares of the MFS Income Fund (fund) provided a total return of 12.52%, at net asset value. This compares with a return of 10.55% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund’s asset allocation decisions, most notably, its holdings of collateralized mortgage obligation (CMO) securities, for which the benchmark has no exposure, coupled with its overweight allocation to both the industrials and financial institutions sectors, contributed to performance. From a quality perspective, the fund’s out-of-benchmark exposure to “BB” and “B” -rated securities benefited relative returns, as bonds within these credit quality segments outperformed the benchmark during the reporting period. Bond selection within both the industrials and financial institutions sectors, particularly within “BBB” and “A” -rated bonds, also supported relative returns. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: Conversely, the fund's duration positioning, particularly along the short end (centered around maturities of less than 5 years) of the yield curve, detracted from relative performance as interest rates generally declined over the reporting period. | |
| 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 10/31/24 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 12.52 % 1.18 % ) 2.55 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 10.55 % (0.23 ) % 1.49 % ∆ 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. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/i | |
| Net Assets | $ 5,670,398,296 | |
| Holdings Count | Holding | 486 | |
| Advisory Fees Paid, Amount | $ 17,041,863 | [13] |
| Investment Company Portfolio Turnover | 50% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 5,670,398,296 Average Effective Maturity (yrs): 9.1 Total Number of Holdings: 486 Average Effective Duration (yrs): 6.1 Total Management Fee ($)#: 17,041,863 Portfolio Turnover Rate (%): 50 # 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 10/31/24) Portfolio structure at value Fixed Income 98.7 % Money Market Funds 1.3 % Composition including fixed income credit quality AAA 7.6 % AA 6.1 % A 12.5 % BBB 26.7 % BB 6.1 % B 5.1 % CCC 0.8 % C 0.0 % U.S. Government 32.1 % Federal Agencies 1.6 % Not Rated 0.1 % Money Market Funds 1.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since November 1, 2023. For more complete information, you may review the fund's next prospectus, which we expect to be available on February 28, 2025 at Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | funds.mfs.com | |
| C000200511 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Fund | |
| Class Name | Class R6 | |
| Trading Symbol | MFIWX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Fund for the period of November 1, 2023 to October 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 $ 0.39 % | |
| Expenses Paid, Amount | $ 41 | |
| Expense Ratio, Percent | 0.39% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended October 31, 2024, Class R6 shares of the MFS Income Fund (fund) provided a total return of 12.61%, at net asset value. This compares with a return of 10.55% for the fund’s benchmark, the Bloomberg U.S. Aggregate Bond Index. As inflation moderated around the globe during the reporting period, several major central banks began to ease monetary policy. Geopolitical strains remained high amid ongoing conflicts in Ukraine and in the Middle East, while relations between China and the US remained tense. At the end of the period, China unveiled a sizable stimulus package aimed at shoring up its property sector and the finances of highly indebted local governments. Toward the end of the period, labor markets loosened modestly, particularly in the US, brightening the inflation outlook as economic growth remained solid. Global equity markets reached record levels during the period as they withstood the adversity of the unsettled geopolitical climate and higher interest rate environment amidst optimism over wide-scale adoption of artificial intelligence and continued healthy earnings growth. Top contributors to performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund’s asset allocation decisions, most notably, its holdings of collateralized mortgage obligation (CMO) securities, for which the benchmark has no exposure, coupled with its overweight allocation to both the industrials and financial institutions sectors, contributed to performance. From a quality perspective, the fund’s out-of-benchmark exposure to “BB” and “B” -rated securities benefited relative returns, as bonds within these credit quality segments outperformed the benchmark during the reporting period. Bond selection within both the industrials and financial institutions sectors, particularly within “BBB” and “A” -rated bonds, also supported relative returns. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: Conversely, the fund's duration positioning, particularly along the short end (centered around maturities of less than 5 years) of the yield curve, detracted from relative performance as interest rates generally declined over the reporting period. | |
| 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 10/31/24 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 12.61 % 1.27 % ) 2.55 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 10.55 % (0.23 ) % 1.38 % * For the period from the commencement of the class's investment operations, March 2, 2018 through October 31, 2024. ∆ Source: FactSet Research Systems Inc. | |
| Performance Inception Date | Mar. 02, 2018 | |
| 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. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r6 | |
| Net Assets | $ 5,670,398,296 | |
| Holdings Count | Holding | 486 | |
| Advisory Fees Paid, Amount | $ 17,041,863 | [14] |
| Investment Company Portfolio Turnover | 50% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 10/31/24 Net Assets ($): 5,670,398,296 Average Effective Maturity (yrs): 9.1 Total Number of Holdings: 486 Average Effective Duration (yrs): 6.1 Total Management Fee ($)#: 17,041,863 Portfolio Turnover Rate (%): 50 # 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 10/31/24) Portfolio structure at value Fixed Income 98.7 % Money Market Funds 1.3 % Composition including fixed income credit quality AAA 7.6 % AA 6.1 % A 12.5 % BBB 26.7 % BB 6.1 % B 5.1 % CCC 0.8 % C 0.0 % U.S. Government 32.1 % Federal Agencies 1.6 % Not Rated 0.1 % Money Market Funds 1.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since November 1, 2023. For more complete information, you may review the fund's next prospectus, which we expect to be available on February 28, 2025 at Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, the management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets: 0.50% up to $1 billion; 0.45% in excess of $1 billion and up to $2.5 billion; 0.40% in excess of $2.5 billion and up to $5 billion; and 0.35% in excess of $5 billion. | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | funds.mfs.com | |
| [1]Includes the effect of any management fee waivers, if applicable.[2]Includes the effect of any management fee waivers, if applicable.[3]Includes the effect of any management fee waivers, if applicable.[4]Includes the effect of any management fee waivers, if applicable.[5]Includes the effect of any management fee waivers, if applicable.[6]Includes the effect of any management fee waivers, if applicable.[7]Includes the effect of any management fee waivers, if applicable.[8]Includes the effect of any management fee waivers, if applicable.[9]Includes the effect of any management fee waivers, if applicable.[10]Includes the effect of any management fee waivers, if applicable.[11]Includes the effect of any management fee waivers, if applicable.[12]Includes the effect of any management fee waivers, if applicable.[13]Includes the effect of any management fee waivers, if applicable.[14]Includes the effect of any management fee waivers, if applicable. | ||
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 80 Months Ended | 120 Months Ended | ||||||||||||||||
| Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2023 | Oct. 31, 2022 | Oct. 31, 2021 | Oct. 31, 2020 | Oct. 31, 2019 | Oct. 31, 2018 | Mar. 02, 2018 | Oct. 31, 2017 | Oct. 31, 2016 | Oct. 31, 2015 | Oct. 31, 2014 | ||||||
| C000006697 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | A with initial sales charge (5.75%) | |||||||||||||||||||
| Average Annual Return, Percent | 18.85% | 9.11% | 9.86% | |||||||||||||||||
| C000006697 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | A without sales charge | |||||||||||||||||||
| Account Value | $ 25,598 | $ 25,598 | $ 25,598 | $ 25,598 | $ 20,299 | $ 18,232 | $ 23,252 | $ 17,498 | $ 15,600 | $ 12,970 | $ 12,546 | $ 9,981 | $ 9,794 | $ 9,425 | ||||||
| Average Annual Return, Percent | 26.10% | 10.41% | 10.51% | |||||||||||||||||
| C000006699 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | B with CDSC (declining over six years from 4% to 0%) | |||||||||||||||||||
| Average Annual Return, Percent | [1] | 21.17% | 9.31% | 9.68% | ||||||||||||||||
| C000006699 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | B without sales charge | |||||||||||||||||||
| Account Value | $ 25,184 | $ 25,184 | 25,184 | $ 25,184 | 20,120 | 18,207 | 23,393 | 17,740 | 15,934 | 13,350 | 13,010 | 10,429 | 10,312 | 10,000 | ||||||
| Average Annual Return, Percent | 25.17% | 9.59% | 9.68% | |||||||||||||||||
| C000006700 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | C with CDSC (1% for 12 months) | |||||||||||||||||||
| Average Annual Return, Percent | [2] | 24.17% | 9.59% | 9.68% | ||||||||||||||||
| C000006700 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | C without sales charge | |||||||||||||||||||
| Account Value | $ 25,187 | $ 25,187 | 25,187 | $ 25,187 | 20,122 | 18,209 | 23,397 | 17,740 | 15,934 | 13,349 | 13,013 | 10,431 | 10,312 | 10,000 | ||||||
| Average Annual Return, Percent | 25.17% | 9.59% | 9.68% | |||||||||||||||||
| C000006701 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | I without sales charge | |||||||||||||||||||
| Account Value | $ 27,829 | $ 27,829 | 27,829 | $ 27,829 | 22,012 | 19,719 | 25,085 | 18,834 | 16,748 | 13,890 | 13,408 | 10,639 | 10,416 | 10,000 | ||||||
| Average Annual Return, Percent | 26.43% | 10.69% | 10.78% | |||||||||||||||||
| C000006703 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R1 without sales charge | |||||||||||||||||||
| Account Value | $ 25,186 | $ 25,186 | 25,186 | $ 25,186 | 20,126 | 18,212 | 23,400 | 17,742 | 15,936 | 13,348 | 13,015 | 10,431 | 10,313 | 10,000 | ||||||
| Average Annual Return, Percent | 25.14% | 9.59% | 9.68% | |||||||||||||||||
| C000006705 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R2 without sales charge | |||||||||||||||||||
| Account Value | $ 26,473 | $ 26,473 | 26,473 | $ 26,473 | 21,046 | 18,950 | 24,226 | 18,281 | 16,337 | 13,619 | 13,208 | 10,537 | 10,365 | 10,000 | ||||||
| Average Annual Return, Percent | 25.79% | 10.14% | 10.23% | |||||||||||||||||
| C000006706 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R3 without sales charge | |||||||||||||||||||
| Account Value | $ 27,145 | $ 27,145 | 27,145 | $ 27,145 | 21,525 | 19,334 | 24,656 | 18,558 | 16,544 | 13,755 | 13,309 | 10,589 | 10,390 | 10,000 | ||||||
| Average Annual Return, Percent | 26.11% | 10.41% | 10.50% | |||||||||||||||||
| C000006698 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R4 without sales charge | |||||||||||||||||||
| Account Value | $ 27,827 | $ 27,827 | 27,827 | $ 27,827 | 22,012 | 19,723 | 25,087 | 18,836 | 16,748 | 13,892 | 13,407 | 10,644 | 10,418 | 10,000 | ||||||
| Average Annual Return, Percent | 26.42% | 10.69% | 10.78% | |||||||||||||||||
| C000126358 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R6 without sales charge | |||||||||||||||||||
| Account Value | $ 28,052 | $ 28,052 | 28,052 | $ 28,052 | 22,171 | 19,849 | 25,226 | 18,924 | 16,815 | 13,938 | 13,439 | 10,658 | 10,427 | 10,000 | ||||||
| Average Annual Return, Percent | 26.53% | 10.78% | 10.87% | |||||||||||||||||
| C000006707 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | A with initial sales charge (4.25%) | |||||||||||||||||||
| Average Annual Return, Percent | 7.46% | 0.06% | 1.87% | |||||||||||||||||
| C000006707 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | A without sales charge | |||||||||||||||||||
| Account Value | $ 12,039 | $ 12,039 | 12,039 | $ 12,039 | 10,727 | 10,517 | 12,562 | 12,235 | 11,493 | 10,275 | 10,568 | 10,119 | 9,506 | 9,575 | ||||||
| Average Annual Return, Percent | 12.23% | 0.93% | 2.32% | |||||||||||||||||
| C000006708 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | B with CDSC (declining over six years from 4% to 0%) | |||||||||||||||||||
| Average Annual Return, Percent | [3] | 7.64% | (0.15%) | 1.59% | ||||||||||||||||
| C000006708 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | B without sales charge | |||||||||||||||||||
| Account Value | $ 11,704 | $ 11,704 | 11,704 | $ 11,704 | 10,484 | 10,358 | 12,464 | 12,231 | 11,589 | 10,416 | 10,808 | 10,426 | 9,850 | 10,000 | ||||||
| Average Annual Return, Percent | 11.64% | 0.20% | 1.59% | |||||||||||||||||
| C000006709 [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | C with CDSC (1% for 12 months) | |||||||||||||||||||
| Average Annual Return, Percent | [4] | 10.47% | 0.19% | 1.58% | ||||||||||||||||
| C000006709 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | C without sales charge | |||||||||||||||||||
| Account Value | $ 11,692 | $ 11,692 | 11,692 | $ 11,692 | 10,489 | 10,364 | 12,458 | 12,225 | 11,582 | 10,424 | 10,807 | 10,425 | 9,864 | 10,000 | ||||||
| Average Annual Return, Percent | 11.47% | 0.19% | 1.58% | |||||||||||||||||
| C000006710 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | I without sales charge | |||||||||||||||||||
| Account Value | $ 12,869 | $ 12,869 | 12,869 | $ 12,869 | 11,437 | 11,186 | 13,312 | 12,952 | 12,136 | 10,821 | 11,103 | 10,621 | 9,937 | 10,000 | ||||||
| Average Annual Return, Percent | 12.52% | 1.18% | 2.55% | |||||||||||||||||
| C000200511 [Member] | Without Sales Load [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | R6 without sales charge | |||||||||||||||||||
| Account Value | $ 11,830 | $ 11,830 | $ 11,830 | $ 11,830 | 10,505 | 10,265 | 12,202 | 11,862 | 11,106 | 9,897 | $ 10,000 | |||||||||
| Average Annual Return, Percent | 12.61% | 1.27% | 2.55% | [5] | ||||||||||||||||
| MSCI All Country World Index net div [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | MSCI All Country World Index (net div) | |||||||||||||||||||
| Account Value | $ 23,808 | $ 23,808 | $ 23,808 | $ 23,808 | 17,929 | 16,225 | 20,270 | 14,766 | 14,078 | 12,503 | 12,568 | 10,201 | 9,997 | 10,000 | ||||||
| Average Annual Return, Percent | [6],[7] | 32.79% | 11.08% | 9.06% | ||||||||||||||||
| Bloomberg U S Aggregate Bond C000200511 Index [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Account Value | $ 10,961 | $ 10,961 | 10,961 | $ 10,961 | 9,915 | 9,880 | 11,717 | 11,774 | 11,088 | 9,943 | ||||||||||
| 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 | $ 11,593 | $ 11,593 | $ 11,593 | $ 11,593 | 10,487 | 10,450 | 12,393 | 12,453 | 11,727 | 10,517 | $ 10,000 | 10,737 | 10,641 | 10,196 | 10,000 | |||||
| Average Annual Return, Percent | 10.55% | [8] | (0.23%) | [8] | 1.38% | [5],[9] | 1.49% | [8] | ||||||||||||
| MSCI All Country World Growth Index net div [Member] | ||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||
| Line Graph and Table Measure Name | MSCI All Country World Growth Index (net div) | |||||||||||||||||||
| Account Value | $ 29,480 | $ 29,480 | $ 29,480 | $ 29,480 | $ 21,483 | $ 18,351 | $ 25,938 | $ 19,257 | $ 15,646 | $ 13,370 | $ 13,223 | $ 10,484 | $ 10,409 | $ 10,000 | ||||||
| Average Annual Return, Percent | [6],[7] | 37.22% | 13.51% | 11.42% | ||||||||||||||||
| [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]For the period from the commencement of the class's investment operations, March 2, 2018 through October 31, 2024.[6]Effective March 1, 2024, the MSCI All Country World Index replaced the MSCI All Country World Growth Index as a broad measure of market performance. The fund continues to use the MSCI All Country World Growth Index as an additional benchmark.[7]Source: FactSet Research Systems Inc.[8]Source: FactSet Research Systems Inc.[9]Source: FactSet Research Systems Inc. | ||||||||||||||||||||
| Shareholder Report, Holdings (Details) | Oct. 31, 2024 |
| C000006697 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006697 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006697 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006697 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006697 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006697 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006697 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006697 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006697 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006697 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006697 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006697 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006697 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006697 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006697 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006697 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006697 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006697 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006697 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006697 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006697 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006697 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006699 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006699 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006699 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006699 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006699 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006699 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006699 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006699 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006699 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006699 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006699 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006699 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006699 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006699 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006699 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006699 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006699 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006699 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006699 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006699 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006699 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006699 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006700 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006700 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006700 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006700 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006700 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006700 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006700 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006700 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006700 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006700 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006700 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006700 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006700 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006700 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006700 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006700 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006700 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006700 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006700 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006700 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006700 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006700 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006701 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006701 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006701 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006701 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006701 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006701 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006701 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006701 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006701 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006701 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006701 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006701 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006701 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006701 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006701 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006701 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006701 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006701 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006701 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006701 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006701 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006701 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006703 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006703 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006703 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006703 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006703 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006703 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006703 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006703 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006703 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006703 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006703 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006703 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006703 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006703 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006703 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006703 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006703 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006703 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006703 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006703 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006703 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006703 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006705 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006705 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006705 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006705 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006705 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006705 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006705 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006705 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006705 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006705 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006705 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006705 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006705 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006705 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006705 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006705 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006705 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006705 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006705 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006705 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006705 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006705 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006706 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006706 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006706 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006706 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006706 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006706 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006706 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006706 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006706 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006706 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006706 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006706 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006706 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006706 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006706 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006706 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006706 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006706 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006706 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006706 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006706 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006706 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006698 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006698 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006698 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006698 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000006698 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006698 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000006698 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006698 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006698 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006698 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006698 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006698 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006698 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006698 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006698 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000006698 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000006698 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006698 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006698 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006698 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000006698 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000006698 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000126358 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000126358 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000126358 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000126358 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000126358 [Member] | Accenture PLC A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000126358 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000126358 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000126358 [Member] | Tencent Holdings Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000126358 [Member] | HDFC Bank Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000126358 [Member] | Canadian Pacific Kansas City Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000126358 [Member] | Other Countries [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000126358 [Member] | CANADA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000126358 [Member] | SWITZERLAND | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000126358 [Member] | CHINA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000126358 [Member] | FRANCE | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.40% |
| C000126358 [Member] | INDIA | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000126358 [Member] | JAPAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000126358 [Member] | KOREA, REPUBLIC OF | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000126358 [Member] | TAIWAN | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000126358 [Member] | UNITED STATES | |
| Holdings [Line Items] | |
| Percent of Total Investments | 70.40% |
| C000126358 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.90% |
| C000126358 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006707 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006707 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.50% |
| C000006707 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.70% |
| C000006707 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006707 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006707 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006707 [Member] | Fitch, C Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006707 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006707 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.60% |
| C000006707 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006707 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006707 [Member] | US Government Debt Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.10% |
| C000006707 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.70% |
| C000006707 [Member] | Federal Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000006708 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006708 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.50% |
| C000006708 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.70% |
| C000006708 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006708 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006708 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006708 [Member] | Fitch, C Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006708 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006708 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.60% |
| C000006708 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006708 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006708 [Member] | US Government Debt Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.10% |
| C000006708 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.70% |
| C000006708 [Member] | Federal Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000006709 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006709 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.50% |
| C000006709 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.70% |
| C000006709 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006709 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006709 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006709 [Member] | Fitch, C Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006709 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006709 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.60% |
| C000006709 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006709 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006709 [Member] | US Government Debt Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.10% |
| C000006709 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.70% |
| C000006709 [Member] | Federal Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000006710 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006710 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.50% |
| C000006710 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.70% |
| C000006710 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006710 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006710 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006710 [Member] | Fitch, C Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006710 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006710 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.60% |
| C000006710 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006710 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000006710 [Member] | US Government Debt Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.10% |
| C000006710 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.70% |
| C000006710 [Member] | Federal Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000200511 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000200511 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.50% |
| C000200511 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.70% |
| C000200511 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000200511 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000200511 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000200511 [Member] | Fitch, C Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000200511 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000200511 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.60% |
| C000200511 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000200511 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000200511 [Member] | US Government Debt Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.10% |
| C000200511 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.70% |
| C000200511 [Member] | Federal Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
