| Form N-CSR Cover | 12 Months Ended |
| Dec. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | MASSACHUSETTS INVESTORS TRUST |
| Entity Central Index Key | 0000063091 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Shareholder Report | 12 Months Ended | |
| Dec. 31, 2024 USD ($) Holding | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSR | |
| Amendment Flag | false | |
| Registrant Name | MASSACHUSETTS INVESTORS TRUST | |
| Entity Central Index Key | 0000063091 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Dec. 31, 2024 | |
| C000002037 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class A | |
| Trading Symbol | MITTX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 31, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | funds.mfs.com | |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A $ 0.70 % | |
| Expenses Paid, Amount | $ 77 | |
| Expense Ratio, Percent | 0.70% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class A shares of the Massachusetts Investors Trust (fund) provided a total return of 19.68 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr A without sales charge 19.68 % 11.54 % 11.26 % A with initial sales charge (5.75%) 12.80 % 10.23 % 10.60 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/a | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [1] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002042 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class B | |
| Trading Symbol | MITBX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 1.45 % | |
| Expenses Paid, Amount | $ 159 | |
| Expense Ratio, Percent | 1.45% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class B shares of the Massachusetts Investors Trust (fund) provided a total return of 18.77 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr B without sales charge 18.77 % 10.71 % 10.42 % B with CDSC (declining over six years from 4% to 0%) × 14.77 % 10.44 % 10.42 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ 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. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/b | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [2] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002043 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class C | |
| Trading Symbol | MITCX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 1.45 % | |
| Expenses Paid, Amount | $ 159 | |
| Expense Ratio, Percent | 1.45% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class C shares of the Massachusetts Investors Trust (fund) provided a total return of 18.75 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr C without sales charge 18.75 % 10.71 % 10.41 % C with CDSC (1% for 12 months) × 17.75 % 10.71 % 10.41 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ 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. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/c | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [3] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002044 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class I | |
| Trading Symbol | MITIX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 0.45 % | |
| Expenses Paid, Amount | $ 49 | |
| Expense Ratio, Percent | 0.45% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class I shares of the Massachusetts Investors Trust (fund) provided a total return of 19.96 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr I without sales charge 19.96 % 11.82 % 11.52 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/i | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [4] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002046 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class R1 | |
| Trading Symbol | MITGX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 1.45 % | |
| Expenses Paid, Amount | $ 159 | |
| Expense Ratio, Percent | 1.45% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class R1 shares of the Massachusetts Investors Trust (fund) provided a total return of 18.78 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R1 without sales charge 18.78 % 10.70 % 10.41 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r1 | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [5] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002048 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class R2 | |
| Trading Symbol | MIRTX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 31, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | funds.mfs.com | |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R2 $ 0.95 % | |
| Expenses Paid, Amount | $ 104 | |
| Expense Ratio, Percent | 0.95% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class R2 shares of the Massachusetts Investors Trust (fund) provided a total return of 19.35 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R2 without sales charge 19.35 % 11.26 % 10.97 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r2 | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [6] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002049 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class R3 | |
| Trading Symbol | MITHX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 31, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | funds.mfs.com | |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last year? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment R3 $ 0.70 % | |
| Expenses Paid, Amount | $ 77 | |
| Expense Ratio, Percent | 0.70% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class R3 shares of the Massachusetts Investors Trust (fund) provided a total return of 19.64 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R3 without sales charge 19.64 % 11.54 % 11.25 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r3 | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [7] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000002038 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class R4 | |
| Trading Symbol | MITDX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 0.45 % | |
| Expenses Paid, Amount | $ 49 | |
| Expense Ratio, Percent | 0.45% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class R4 shares of the Massachusetts Investors Trust (fund) provided a total return of 19.98 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R4 without sales charge 19.98 % 11.82 % 11.52 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r4 | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [8] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| C000113374 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Massachusetts Investors Trust | |
| Class Name | Class R6 | |
| Trading Symbol | MITJX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Massachusetts Investors Trust for the period of January 1, 2024 to December 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 $ 0.38 % | |
| Expenses Paid, Amount | $ 42 | |
| Expense Ratio, Percent | 0.38% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Class R6 shares of the Massachusetts Investors Trust (fund) provided a total return of 20.05 25.02 Moderating inflation pressures allowed many global central banks to ease monetary policy during the period. However, the pace of disinflation slowed toward the end of the period, particularly in the United States. 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 a higher interest rate environment amid optimism over the wide-scale adoption of artificial intelligence and continued healthy earnings growth. Global bond yields climbed to close out the calendar year on the back of the US election result, resilient economic growth, and concerns that global disinflationary progress may have stalled. Reflecting increased inflation uncertainty, market expectations for future Federal Reserve interest rate cuts in 2025 have been pared back while already compressed credit spreads tightened further. Global bond market volatility, as measured by the Merrill Lynch Option Volatility Estimate (MOVE) index, declined in the fourth quarter after peaking before the US election. Top contributors to performance relative to the Standard & Poor's 500 Stock Index: Security selection within the industrials sector aided relative performance. Stock selection and, to a lesser extent, an overweight position in the financials sector also benefited relative returns. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within the information technology, communication services, and consumer staples 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 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 12/31/24 This table shows the average annual total returns of the class of shares noted for the periods shown, both with (if any) and without sales charges. It also shows the average annual total returns of a broad measure of market performance over the same periods. Share Class 1-yr 5-yr 10-yr R6 without sales charge 20.05 % 11.91 % 11.62 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index ∆ 25.02 % 14.53 % 13.10 % ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/r6 | |
| Net Assets | $ 6,788,255,574 | |
| Holdings Count | Holding | 65 | |
| Advisory Fees Paid, Amount | $ 22,470,026 | [9] |
| Investment Company Portfolio Turnover | 25% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 6,788,255,574 Total Management Fee ($)#: 22,470,026 Total Number of Holdings: 65 Portfolio Turnover Rate (%): 25 # 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 12/31/24) Portfolio structure Equities 99.1 % Money Market Funds 0.9 % Equity sectors Information Technology 28.1 % Financials 18.2 % Industrials 11.5 % Health Care 10.3 % Consumer Discretionary 7.4 % Communication Services 7.1 % Consumer Staples 7.1 % Utilities 3.4 % Energy 3.2 % Real Estate 1.5 % Materials 1.3 % Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 8.2 % Alphabet, Inc., "A" 5.6 % NVIDIA Corp. 5.5 % Amazon.com, Inc. 5.3 % Apple, Inc. 4.5 % JPMorgan Chase & Co. 2.8 % Visa, Inc., "A" 2.7 % Salesforce, Inc. 2.5 % Fiserv, Inc. 2.2 % ConocoPhillips 1.9 % | |
| [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. | ||
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | |||||||||||
| Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | ||
| C000002037 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | A with initial sales charge (5.75%) | |||||||||||||
| Average Annual Return, Percent | 12.80% | 10.23% | 10.60% | |||||||||||
| C000002037 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | A without sales charge | |||||||||||||
| Account Value | $ 27,396 | $ 27,396 | $ 27,396 | $ 22,891 | $ 19,213 | $ 22,964 | $ 18,107 | $ 15,867 | $ 12,028 | $ 12,703 | $ 10,280 | $ 9,451 | $ 9,425 | |
| Average Annual Return, Percent | 19.68% | 11.54% | 11.26% | |||||||||||
| C000002042 [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] | 14.77% | 10.44% | 10.42% | ||||||||||
| C000002042 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | B without sales charge | |||||||||||||
| Account Value | $ 26,943 | $ 26,943 | $ 26,943 | 22,684 | 19,180 | 23,099 | 18,350 | 16,202 | 12,373 | 13,171 | 10,742 | 9,952 | 10,000 | |
| Average Annual Return, Percent | 18.77% | 10.71% | 10.42% | |||||||||||
| C000002043 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | C with CDSC (1% for 12 months) | |||||||||||||
| Average Annual Return, Percent | [2] | 17.75% | 10.71% | 10.41% | ||||||||||
| C000002043 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | C without sales charge | |||||||||||||
| Account Value | $ 26,927 | $ 26,927 | $ 26,927 | 22,675 | 19,173 | 23,092 | 18,344 | 16,194 | 12,373 | 13,169 | 10,739 | 9,946 | 10,000 | |
| Average Annual Return, Percent | 18.75% | 10.71% | 10.41% | |||||||||||
| C000002044 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | I without sales charge | |||||||||||||
| Account Value | $ 29,764 | $ 29,764 | $ 29,764 | 24,812 | 20,777 | 24,771 | 19,476 | 17,026 | 12,876 | 13,565 | 10,958 | 10,046 | 10,000 | |
| Average Annual Return, Percent | 19.96% | 11.82% | 11.52% | |||||||||||
| C000002046 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | R1 without sales charge | |||||||||||||
| Account Value | $ 26,931 | $ 26,931 | $ 26,931 | 22,673 | 19,174 | 23,091 | 18,341 | 16,198 | 12,375 | 13,169 | 10,743 | 9,949 | 10,000 | |
| Average Annual Return, Percent | 18.78% | 10.70% | 10.41% | |||||||||||
| C000002048 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | R2 without sales charge | |||||||||||||
| Account Value | $ 28,315 | $ 28,315 | $ 28,315 | 23,725 | 19,960 | 23,913 | 18,900 | 16,607 | 12,624 | 13,367 | 10,851 | 9,997 | 10,000 | |
| Average Annual Return, Percent | 19.35% | 11.26% | 10.97% | |||||||||||
| C000002049 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | R3 without sales charge | |||||||||||||
| Account Value | $ 29,032 | $ 29,032 | $ 29,032 | 24,266 | 20,365 | 24,338 | 19,186 | 16,815 | 12,753 | 13,469 | 10,906 | 10,026 | 10,000 | |
| Average Annual Return, Percent | 19.64% | 11.54% | 11.25% | |||||||||||
| C000002038 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | R4 without sales charge | |||||||||||||
| Account Value | $ 29,765 | $ 29,765 | $ 29,765 | 24,808 | 20,769 | 24,767 | 19,477 | 17,028 | 12,878 | 13,570 | 10,958 | 10,048 | 10,000 | |
| Average Annual Return, Percent | 19.98% | 11.82% | 11.52% | |||||||||||
| C000113374 [Member] | Without Sales Load [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | R6 without sales charge | |||||||||||||
| Account Value | $ 30,011 | $ 30,011 | $ 30,011 | 24,999 | 20,912 | 24,914 | 19,578 | 17,099 | 12,921 | 13,606 | 10,979 | 10,058 | 10,000 | |
| Average Annual Return, Percent | 20.05% | 11.91% | 11.62% | |||||||||||
| Standard And Poor s 500 Stock Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Standard & Poor's 500 Stock Index | |||||||||||||
| Account Value | $ 34,254 | $ 34,254 | $ 34,254 | $ 27,399 | $ 21,696 | $ 26,494 | $ 20,585 | $ 17,386 | $ 13,223 | $ 13,829 | $ 11,351 | $ 10,138 | $ 10,000 | |
| Average Annual Return, Percent | [3] | 25.02% | 14.53% | 13.10% | ||||||||||
| [1]Assuming redemption at the end of the applicable period.[2]Assuming redemption at the end of the applicable period.[3]Source: FactSet Research Systems Inc. | ||||||||||||||
| Shareholder Report, Holdings (Details) | Dec. 31, 2024 |
| C000002037 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002037 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002037 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002037 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002037 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002037 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002037 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002037 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002037 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002037 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002037 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002037 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002037 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002037 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002037 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002037 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002037 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002037 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002037 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002037 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002037 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002037 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002037 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002042 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002042 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002042 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002042 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002042 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002042 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002042 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002042 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002042 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002042 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002042 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002042 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002042 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002042 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002042 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002042 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002042 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002042 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002042 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002042 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002042 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002042 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002042 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002043 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002043 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002043 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002043 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002043 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002043 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002043 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002043 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002043 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002043 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002043 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002043 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002043 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002043 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002043 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002043 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002043 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002043 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002043 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002043 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002043 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002043 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002043 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002044 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002044 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002044 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002044 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002044 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002044 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002044 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002044 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002044 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002044 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002044 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002044 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002044 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002044 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002044 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002044 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002044 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002044 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002044 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002044 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002044 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002044 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002044 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002046 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002046 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002046 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002046 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002046 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002046 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002046 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002046 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002046 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002046 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002046 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002046 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002046 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002046 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002046 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002046 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002046 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002046 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002046 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002046 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002046 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002046 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002046 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002048 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002048 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002048 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002048 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002048 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002048 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002048 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002048 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002048 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002048 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002048 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002048 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002048 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002048 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002048 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002048 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002048 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002048 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002048 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002048 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002048 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002048 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002048 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002049 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002049 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002049 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002049 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002049 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002049 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002049 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002049 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002049 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002049 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002049 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002049 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002049 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002049 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002049 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002049 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002049 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002049 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002049 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002049 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002049 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002049 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002049 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000002038 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000002038 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000002038 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000002038 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000002038 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000002038 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000002038 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000002038 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000002038 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000002038 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000002038 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000002038 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000002038 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000002038 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000002038 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002038 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000002038 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000002038 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000002038 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000002038 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000002038 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000002038 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000002038 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000113374 [Member] | Microsoft Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.20% |
| C000113374 [Member] | Alphabet Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000113374 [Member] | NVIDIA Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000113374 [Member] | Amazon com Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000113374 [Member] | Apple Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000113374 [Member] | JPMorgan Chase And Co [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.80% |
| C000113374 [Member] | Visa Inc A [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000113374 [Member] | Salesforce Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.50% |
| C000113374 [Member] | Fiserv Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.20% |
| C000113374 [Member] | ConocoPhillips [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000113374 [Member] | Energy Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000113374 [Member] | Financial Services Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.20% |
| C000113374 [Member] | Healthcare Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.30% |
| C000113374 [Member] | Real Estate Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000113374 [Member] | Communications Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000113374 [Member] | Consumer Discretionary Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.40% |
| C000113374 [Member] | Consumer Staples Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000113374 [Member] | Industrial Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.50% |
| C000113374 [Member] | Information Technology Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 28.10% |
| C000113374 [Member] | Materials Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000113374 [Member] | Utilities Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000113374 [Member] | Equity [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000113374 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
