| Form N-CSR Cover | 12 Months Ended |
| Dec. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | MFS VARIABLE INSURANCE TRUST II |
| Entity Central Index Key | 0000719269 |
| 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 | MFS VARIABLE INSURANCE TRUST II | |
| Entity Central Index Key | 0000719269 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Dec. 31, 2024 | |
| C000007237 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Corporate Bond Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Corporate Bond Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.63 % | |
| Expenses Paid, Amount | $ 64 | |
| Expense Ratio, Percent | 0.63% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Corporate Bond Portfolio (fund) provided a total return of 3.00 1.25 2.03% 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 Bloomberg U.S. Credit Index: From a quality perspective, the fund's exposure to BB- and B-rated bonds, for which the benchmark has no exposure, helped relative performance. Additionally, the fund's overweight exposure and security selection within BBB-rated bonds also supported relative returns. From a sector perspective, bond selection within the banking, consumer non-cyclicals, and consumer cyclicals sectors aided relative results. Top detractors from performance relative to the Bloomberg U.S. Credit Index: From a quality perspective, an underweight allocation to A-rated bonds 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 Initial Class 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. | |
| 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. 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 Initial Class 3.00 % 0.49 % 2.54 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Credit Index +∆ 2.03 % 0.23 % 2.29 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Credit Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Credit Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Credit Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Credit Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 137,429,760 | |
| Holdings Count | Holding | 389 | |
| Advisory Fees Paid, Amount | $ 814,497 | [1] |
| Investment Company Portfolio Turnover | 49% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 137,429,760 Average Effective Maturity (yrs): 10.2 Total Number of Holdings: 389 Average Effective Duration (yrs): 6.6 Total Management Fee ($)#: 814,497 Portfolio Turnover Rate (%): 49 # 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 Fixed Income 97.6 % Money Market Funds 2.4 % Issuer country weightings United States 72.8 % Canada 4.6 % Australia 3.4 % United Kingdom 3.3 % Ireland 2.0 % Japan 1.9 % Italy 1.6 % Switzerland 1.4 % Bermuda 1.1 % Other Countries 7.9 % Composition including fixed income credit quality AAA 3.7 % AA 3.8 % A 27.7 % BBB 50.3 % BB 6.9 % B 1.7 % U.S. Government 3.4 % Not Rated 0.1 % Money Market Funds 2.4 % 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. | |
| C000007238 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Corporate Bond Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Corporate Bond Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 0.88 % | |
| Expenses Paid, Amount | $ 89 | |
| Expense Ratio, Percent | 0.88% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Corporate Bond Portfolio (fund) provided a total return of 2.70 1.25 2.03% 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 Bloomberg U.S. Credit Index: From a quality perspective, the fund's exposure to BB- and B-rated bonds, for which the benchmark has no exposure, helped relative performance. Additionally, the fund's overweight exposure and security selection within BBB-rated bonds also supported relative returns. From a sector perspective, bond selection within the banking, consumer non-cyclicals, and consumer cyclicals sectors aided relative results. Top detractors from performance relative to the Bloomberg U.S. Credit Index: From a quality perspective, an underweight allocation to A-rated bonds 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 Service Class 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. | |
| 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. 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 Service Class 2.70 % 0.23 % 2.27 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Credit Index +∆ 2.03 % 0.23 % 2.29 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Credit Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Credit Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Credit Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Credit Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 137,429,760 | |
| Holdings Count | Holding | 389 | |
| Advisory Fees Paid, Amount | $ 814,497 | [2] |
| Investment Company Portfolio Turnover | 49% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 137,429,760 Average Effective Maturity (yrs): 10.2 Total Number of Holdings: 389 Average Effective Duration (yrs): 6.6 Total Management Fee ($)#: 814,497 Portfolio Turnover Rate (%): 49 # 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 Fixed Income 97.6 % Money Market Funds 2.4 % Issuer country weightings United States 72.8 % Canada 4.6 % Australia 3.4 % United Kingdom 3.3 % Ireland 2.0 % Japan 1.9 % Italy 1.6 % Switzerland 1.4 % Bermuda 1.1 % Other Countries 7.9 % Composition including fixed income credit quality AAA 3.7 % AA 3.8 % A 27.7 % BBB 50.3 % BB 6.9 % B 1.7 % U.S. Government 3.4 % Not Rated 0.1 % Money Market Funds 2.4 % 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. | |
| C000007239 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Government Securities Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Government Securities Portfolio 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 insurancefunds.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 | insurancefunds.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 Initial Class $ 0.58 % | |
| Expenses Paid, Amount | $ 58 | |
| Expense Ratio, Percent | 0.58% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Government Securities Portfolio (fund) provided a total return of 0.77 1.25 0.83% 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 Bloomberg U.S. Government/Mortgage Index: Yield curve positioning, particularly the fund's greater exposure to shifts in the short end (centered around maturities 2 years or less) and lesser exposure to shifts in the long end (centered around maturities of 30 years) of the yield curve, contributed to relative performance. From a sector perspective, the fund's exposure to the commercial mortgage-backed securities (CMBS), collateralized loan obligations (CLO), and collateralized mortgage obligations (CMO) sectors, for which the benchmark has no exposure, also benefited relative returns. Top detractors from performance relative to the Bloomberg U.S. Government/Mortgage Index: The fund's slightly shorter duration stance detracted from relative returns as the yield curve steepened throughout 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 Initial Class 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. | |
| 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. 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 Initial Class 0.77 % (0.79 ) % 0.66 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Government/Mortgage Index +∆ 0.83 % (0.67 ) % 0.88 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Government/Mortgage Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Government/Mortgage Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Government/Mortgage Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Government/Mortgage Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Material Change Date | Aug. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 282,621,709 | |
| Holdings Count | Holding | 576 | |
| Advisory Fees Paid, Amount | $ 1,565,662 | [3] |
| Investment Company Portfolio Turnover | 128% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 282,621,709 Average Effective Maturity (yrs): 7.2 Total Number of Holdings: 576 Average Effective Duration (yrs): 5.9 Total Management Fee ($)#: 1,565,662 Portfolio Turnover Rate (%): 128 # 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 Fixed Income 89.8 % Money Market Funds 10.2 % Composition including fixed income credit quality AAA 6.7 % AA 1.2 % A 0.7 % BBB 0.0 % U.S. Government 24.0 % Federal Agencies 57.2 % Money Market Funds 10.2 % 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 January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.56% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.56% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007240 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Government Securities Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Government Securities Portfolio 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 insurancefunds.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 | insurancefunds.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 Service Class $ 0.83 % | |
| Expenses Paid, Amount | $ 83 | |
| Expense Ratio, Percent | 0.83% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Government Securities Portfolio (fund) provided a total return of 0.53 1.25 0.83% 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 Bloomberg U.S. Government/Mortgage Index: Yield curve positioning, particularly the fund's greater exposure to shifts in the short end (centered around maturities 2 years or less) and lesser exposure to shifts in the long end (centered around maturities of 30 years) of the yield curve, contributed to relative performance. From a sector perspective, the fund's exposure to the commercial mortgage-backed securities (CMBS), collateralized loan obligations (CLO), and collateralized mortgage obligations (CMO) sectors, for which the benchmark has no exposure, also benefited relative returns. Top detractors from performance relative to the Bloomberg U.S. Government/Mortgage Index: The fund's slightly shorter duration stance detracted from relative returns as the yield curve steepened throughout 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 Service Class 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. | |
| 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. 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 Service Class 0.53 % (1.04 ) % 0.41 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Government/Mortgage Index +∆ 0.83 % (0.67 ) % 0.88 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Government/Mortgage Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Government/Mortgage Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Government/Mortgage Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Government/Mortgage Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Material Change Date | Aug. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 282,621,709 | |
| Holdings Count | Holding | 576 | |
| Advisory Fees Paid, Amount | $ 1,565,662 | [4] |
| Investment Company Portfolio Turnover | 128% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 282,621,709 Average Effective Maturity (yrs): 7.2 Total Number of Holdings: 576 Average Effective Duration (yrs): 5.9 Total Management Fee ($)#: 1,565,662 Portfolio Turnover Rate (%): 128 # 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 Fixed Income 89.8 % Money Market Funds 10.2 % Composition including fixed income credit quality AAA 6.7 % AA 1.2 % A 0.7 % BBB 0.0 % U.S. Government 24.0 % Federal Agencies 57.2 % Money Market Funds 10.2 % 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 January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.81% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.81% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007241 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® High Yield Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS High Yield Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.72 % | |
| Expenses Paid, Amount | $ 74 | |
| Expense Ratio, Percent | 0.72% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS High Yield Portfolio (fund) provided a total return of 6.92 1.25 8.19% 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 Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index: From a quality perspective, security selection within B-rated bonds benefited relative performance. From a sector perspective, bond selection within the energy sector also helped relative results. Top detractors from performance relative to the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index: From a quality perspective, an underweight exposure to CC-rated bonds, and security selection within CCC-rated bonds, held back relative performance. From a sector perspective, bond selection within both the consumer cyclicals and consumer non-cyclicals sectors, coupled with the fund's overweight exposure to the capital goods and insurance sectors, dampened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class 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. | |
| 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. 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 Initial Class 6.92 % 3.18 % 4.23 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index +∆ 8.19 % 4.20 % 5.16 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 229,711,966 | |
| Holdings Count | Holding | 349 | |
| Advisory Fees Paid, Amount | $ 1,636,285 | [5] |
| Investment Company Portfolio Turnover | 58% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 229,711,966 Average Effective Maturity (yrs): 4.2 Total Number of Holdings: 349 Average Effective Duration (yrs): 3.1 Total Management Fee ($)#: 1,636,285 Portfolio Turnover Rate (%): 58 # 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 Fixed Income ~ 98.6 % Money Market Funds 1.2 % Equities 0.2 % Composition including fixed income credit quality BBB 0.6 % BB 44.4 % B 37.8 % CCC 13.8 % CC 0.4 % C 0.4 % Not Rated 1.2 % Non-Fixed Income 0.2 % Money Market Funds 1.2 % 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. ~ The fund invests a portion of its assets in Exchange-Traded Funds (ETFs) or Options on ETFs to gain fixed income exposure. Percentages include the direct exposure from investing in ETFs or Options on ETFs and not the indirect exposure to the underlying holdings. | |
| 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. | |
| C000007242 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® High Yield Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS High Yield Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 0.97 % | |
| Expenses Paid, Amount | $ 100 | |
| Expense Ratio, Percent | 0.97% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS High Yield Portfolio (fund) provided a total return of 6.53 1.25 8.19% 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 Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index: From a quality perspective, security selection within B-rated bonds benefited relative performance. From a sector perspective, bond selection within the energy sector also helped relative results. Top detractors from performance relative to the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index: From a quality perspective, an underweight exposure to CC-rated bonds, and security selection within CCC-rated bonds, held back relative performance. From a sector perspective, bond selection within both the consumer cyclicals and consumer non-cyclicals sectors, coupled with the fund's overweight exposure to the capital goods and insurance sectors, dampened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class 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. | |
| 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. 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 Service Class 6.53 % 2.93 % 3.98 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index +∆ 1.25 % (0.33 ) % 1.35 % Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index +∆ 8.19 % 4.20 % 5.16 % + Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 229,711,966 | |
| Holdings Count | Holding | 349 | |
| Advisory Fees Paid, Amount | $ 1,636,285 | [6] |
| Investment Company Portfolio Turnover | 58% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 229,711,966 Average Effective Maturity (yrs): 4.2 Total Number of Holdings: 349 Average Effective Duration (yrs): 3.1 Total Management Fee ($)#: 1,636,285 Portfolio Turnover Rate (%): 58 # 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 Fixed Income ~ 98.6 % Money Market Funds 1.2 % Equities 0.2 % Composition including fixed income credit quality BBB 0.6 % BB 44.4 % B 37.8 % CCC 13.8 % CC 0.4 % C 0.4 % Not Rated 1.2 % Non-Fixed Income 0.2 % Money Market Funds 1.2 % 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. ~ The fund invests a portion of its assets in Exchange-Traded Funds (ETFs) or Options on ETFs to gain fixed income exposure. Percentages include the direct exposure from investing in ETFs or Options on ETFs and not the indirect exposure to the underlying holdings. | |
| 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. | |
| C000007243 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® International Growth Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS International Growth Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.88 % | |
| Expenses Paid, Amount | $ 92 | |
| Expense Ratio, Percent | 0.88% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS International Growth Portfolio (fund) provided a total return of 9.00 5.53 5.07% 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 MSCI All Country World (ex-US) Growth Index: Security selection within the industrials, information technology, and materials sectors contributed to relative performance. In addition, security selection and an underweight position in the health care sector supported relative results. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index: Security selection and an overweight position in the consumer staples sector detracted from relative performance. An underweight position and security selection in the communication services sector further held back relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class 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. | |
| 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. 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 Initial Class 9.00 % 6.12 % 7.83 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 5.53 % 4.10 % 4.80 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 5.07 % 3.44 % 5.35 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 277,493,656 | |
| Holdings Count | Holding | 86 | |
| Advisory Fees Paid, Amount | $ 2,354,926 | [7] |
| Investment Company Portfolio Turnover | 19% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 277,493,656 Total Management Fee ($)#: 2,354,926 Total Number of Holdings: 86 Portfolio Turnover Rate (%): 19 # 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 98.0 % Money Market Funds 2.0 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 5.5 % SAP SE 5.1 % Schneider Electric SE 3.8 % Hitachi Ltd. 3.7 % Roche Holding AG 3.1 % Nestle S.A. 3.0 % LVMH Moet Hennessy Louis Vuitton SE 2.5 % Linde PLC 2.4 % EssilorLuxottica 2.3 % Amadeus IT Group S.A. 2.2 % Issuer country weightings France 15.0 % Germany 11.6 % Japan 10.2 % United Kingdom 8.4 % Switzerland 7.6 % Taiwan 7.0 % Canada 7.0 % United States 4.4 % Netherlands 4.1 % Other Countries 24.7 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 5.5 % SAP SE 5.1 % Schneider Electric SE 3.8 % Hitachi Ltd. 3.7 % Roche Holding AG 3.1 % Nestle S.A. 3.0 % LVMH Moet Hennessy Louis Vuitton SE 2.5 % Linde PLC 2.4 % EssilorLuxottica 2.3 % Amadeus IT Group S.A. 2.2 % | |
| C000007244 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® International Growth Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS International Growth Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.13 % | |
| Expenses Paid, Amount | $ 118 | |
| Expense Ratio, Percent | 1.13% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS International Growth Portfolio (fund) provided a total return of 8.76 5.53 5.07% 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 MSCI All Country World (ex-US) Growth Index: Security selection within the industrials, information technology, and materials sectors contributed to relative performance. In addition, security selection and an underweight position in the health care sector supported relative results. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World (ex-US) Growth Index: Security selection and an overweight position in the consumer staples sector detracted from relative performance. An underweight position and security selection in the communication services sector further held back relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class 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. | |
| 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. 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 Service Class 8.76 % 5.84 % 7.56 % Comparative Benchmark(s) MSCI All Country World (ex-US) Index (net div) +∆ 5.53 % 4.10 % 4.80 % MSCI All Country World (ex-US) Growth Index (net div) +∆ 5.07 % 3.44 % 5.35 % + Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 277,493,656 | |
| Holdings Count | Holding | 86 | |
| Advisory Fees Paid, Amount | $ 2,354,926 | [8] |
| Investment Company Portfolio Turnover | 19% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 277,493,656 Total Management Fee ($)#: 2,354,926 Total Number of Holdings: 86 Portfolio Turnover Rate (%): 19 # 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 98.0 % Money Market Funds 2.0 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 5.5 % SAP SE 5.1 % Schneider Electric SE 3.8 % Hitachi Ltd. 3.7 % Roche Holding AG 3.1 % Nestle S.A. 3.0 % LVMH Moet Hennessy Louis Vuitton SE 2.5 % Linde PLC 2.4 % EssilorLuxottica 2.3 % Amadeus IT Group S.A. 2.2 % Issuer country weightings France 15.0 % Germany 11.6 % Japan 10.2 % United Kingdom 8.4 % Switzerland 7.6 % Taiwan 7.0 % Canada 7.0 % United States 4.4 % Netherlands 4.1 % Other Countries 24.7 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 5.5 % SAP SE 5.1 % Schneider Electric SE 3.8 % Hitachi Ltd. 3.7 % Roche Holding AG 3.1 % Nestle S.A. 3.0 % LVMH Moet Hennessy Louis Vuitton SE 2.5 % Linde PLC 2.4 % EssilorLuxottica 2.3 % Amadeus IT Group S.A. 2.2 % | |
| C000007245 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® International Intrinsic Value Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS International Intrinsic Value Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.89 % | |
| Expenses Paid, Amount | $ 92 | |
| Expense Ratio, Percent | 0.89% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS International Intrinsic Value Portfolio (fund) provided a total return of 7.25 3.82 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 MSCI EAFE Index: The combination of stock selection and an overweight allocation to both the financials and information technology sectors contributed to relative performance. In addition, stock selection within the materials sector supported relative results. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, benefited relative performance. Top detractors from performance relative to the MSCI EAFE Index: The combination of an overweight allocation and security selection within the energy sector detracted from relative performance. Not owning any stocks within the communication services sector also weakened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 7.25 % 5.15 % 7.53 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 3.82 % 4.73 % 5.20 % ∆ 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/ic | |
| Net Assets | $ 1,348,257,083 | |
| Holdings Count | Holding | 90 | |
| Advisory Fees Paid, Amount | $ 11,923,047 | [9] |
| Investment Company Portfolio Turnover | 15% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 1,348,257,083 Total Management Fee ($)#: 11,923,047 Total Number of Holdings: 90 Portfolio Turnover Rate (%): 15 # 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 97.8 % Money Market Funds 2.2 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.6 % Schneider Electric SE 3.1 % NatWest Group PLC 2.9 % Franco-Nevada Corp. 2.9 % TotalEnergies SE 2.6 % Legrand S.A. 2.5 % Deutsche Boerse AG 2.3 % SAP SE 2.3 % AIB Group PLC 2.2 % Resona Holdings, Inc. 2.2 % Issuer country weightings United Kingdom 18.0 % France 16.3 % Japan 13.4 % United States 9.3 % Germany 8.1 % Switzerland 7.2 % Canada 5.0 % Ireland 4.5 % Spain 4.2 % Other Countries 14.0 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.6 % Schneider Electric SE 3.1 % NatWest Group PLC 2.9 % Franco-Nevada Corp. 2.9 % TotalEnergies SE 2.6 % Legrand S.A. 2.5 % Deutsche Boerse AG 2.3 % SAP SE 2.3 % AIB Group PLC 2.2 % Resona Holdings, Inc. 2.2 % | |
| C000007246 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® International Intrinsic Value Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS International Intrinsic Value Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.14 % | |
| Expenses Paid, Amount | $ 118 | |
| Expense Ratio, Percent | 1.14% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS International Intrinsic Value Portfolio (fund) provided a total return of 6.97 3.82 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 MSCI EAFE Index: The combination of stock selection and an overweight allocation to both the financials and information technology sectors contributed to relative performance. In addition, stock selection within the materials sector supported relative results. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, benefited relative performance. Top detractors from performance relative to the MSCI EAFE Index: The combination of an overweight allocation and security selection within the energy sector detracted from relative performance. Not owning any stocks within the communication services sector also weakened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 6.97 % 4.88 % 7.26 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 3.82 % 4.73 % 5.20 % ∆ 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/sc | |
| Net Assets | $ 1,348,257,083 | |
| Holdings Count | Holding | 90 | |
| Advisory Fees Paid, Amount | $ 11,923,047 | [10] |
| Investment Company Portfolio Turnover | 15% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 1,348,257,083 Total Management Fee ($)#: 11,923,047 Total Number of Holdings: 90 Portfolio Turnover Rate (%): 15 # 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 97.8 % Money Market Funds 2.2 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.6 % Schneider Electric SE 3.1 % NatWest Group PLC 2.9 % Franco-Nevada Corp. 2.9 % TotalEnergies SE 2.6 % Legrand S.A. 2.5 % Deutsche Boerse AG 2.3 % SAP SE 2.3 % AIB Group PLC 2.2 % Resona Holdings, Inc. 2.2 % Issuer country weightings United Kingdom 18.0 % France 16.3 % Japan 13.4 % United States 9.3 % Germany 8.1 % Switzerland 7.2 % Canada 5.0 % Ireland 4.5 % Spain 4.2 % Other Countries 14.0 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.6 % Schneider Electric SE 3.1 % NatWest Group PLC 2.9 % Franco-Nevada Corp. 2.9 % TotalEnergies SE 2.6 % Legrand S.A. 2.5 % Deutsche Boerse AG 2.3 % SAP SE 2.3 % AIB Group PLC 2.2 % Resona Holdings, Inc. 2.2 % | |
| C000007247 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Massachusetts Investors Growth Stock Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Massachusetts Investors Growth Stock Portfolio 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 insurancefunds.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 | insurancefunds.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 Initial Class $ 0.73 % | |
| Expenses Paid, Amount | $ 79 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Massachusetts Investors Growth Stock Portfolio (fund) provided a total return of 16.27 23.81 ® ® 33.36% 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 Russell 1000 ® Security selection within the industrials sector benefited relative performance. Top detractors from performance relative to the Russell 1000 ® Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. The combination of stock selection and an overweight allocation to the consumer staples sector also hindered relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class 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. | |
| 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. 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 Initial Class 16.27 % 12.43 % 13.18 % Comparative Benchmark(s) Russell 3000 ® 23.81 % 13.86 % 12.55 % Russell 1000 ® 33.36 % 18.96 % 16.78 % + Effective May 1, 2024, the Russell 3000 ® ® ® ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Russell 3000 ® ® ® | |
| Material Change Date | Aug. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 993,188,129 | |
| Holdings Count | Holding | 55 | |
| Advisory Fees Paid, Amount | $ 7,425,841 | [11] |
| Investment Company Portfolio Turnover | 19% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 993,188,129 Total Management Fee ($)#: 7,425,841 Total Number of Holdings: 55 Portfolio Turnover Rate (%): 19 # 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 38.1 % Financials 14.1 % Health Care 11.7 % Industrials 8.7 % Consumer Discretionary 7.8 % Communication Services 7.5 % Consumer Staples 6.4 % Utilities 2.0 % Real Estate 1.7 % Materials 1.1 % Top ten holdings Microsoft Corp. 13.4 % Apple, Inc. 5.8 % NVIDIA Corp. 5.5 % Visa, Inc., "A" 4.4 % Alphabet, Inc., "A" 4.2 % Accenture PLC, "A" 3.5 % Aon PLC 2.5 % Salesforce, Inc. 2.4 % Church & Dwight Co., Inc. 2.4 % Agilent Technologies, Inc. 2.2 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 13.4 % Apple, Inc. 5.8 % NVIDIA Corp. 5.5 % Visa, Inc., "A" 4.4 % Alphabet, Inc., "A" 4.2 % Accenture PLC, "A" 3.5 % Aon PLC 2.5 % Salesforce, Inc. 2.4 % Church & Dwight Co., Inc. 2.4 % Agilent Technologies, Inc. 2.2 % | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.72% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.72% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007248 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Massachusetts Investors Growth Stock Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Massachusetts Investors Growth Stock Portfolio 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 insurancefunds.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 | insurancefunds.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 Service Class $ 0.98 % | |
| Expenses Paid, Amount | $ 106 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Massachusetts Investors Growth Stock Portfolio (fund) provided a total return of 15.98 23.81 ® ® 33.36% 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 Russell 1000 ® Security selection within the industrials sector benefited relative performance. Top detractors from performance relative to the Russell 1000 ® Security selection within both the information technology and consumer discretionary sectors detracted from relative performance. The combination of stock selection and an overweight allocation to the consumer staples sector also hindered relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class 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. | |
| 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. 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 Service Class 15.98 % 12.16 % 12.91 % Comparative Benchmark(s) Russell 3000 ® 23.81 % 13.86 % 12.55 % Russell 1000 ® 33.36 % 18.96 % 16.78 % + Effective May 1, 2024, the Russell 3000 ® ® ® ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Russell 3000 ® ® ® | |
| Material Change Date | Aug. 01, 2024 | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 993,188,129 | |
| Holdings Count | Holding | 55 | |
| Advisory Fees Paid, Amount | $ 7,425,841 | [12] |
| Investment Company Portfolio Turnover | 19% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 993,188,129 Total Management Fee ($)#: 7,425,841 Total Number of Holdings: 55 Portfolio Turnover Rate (%): 19 # 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 38.1 % Financials 14.1 % Health Care 11.7 % Industrials 8.7 % Consumer Discretionary 7.8 % Communication Services 7.5 % Consumer Staples 6.4 % Utilities 2.0 % Real Estate 1.7 % Materials 1.1 % Top ten holdings Microsoft Corp. 13.4 % Apple, Inc. 5.8 % NVIDIA Corp. 5.5 % Visa, Inc., "A" 4.4 % Alphabet, Inc., "A" 4.2 % Accenture PLC, "A" 3.5 % Aon PLC 2.5 % Salesforce, Inc. 2.4 % Church & Dwight Co., Inc. 2.4 % Agilent Technologies, Inc. 2.2 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 13.4 % Apple, Inc. 5.8 % NVIDIA Corp. 5.5 % Visa, Inc., "A" 4.4 % Alphabet, Inc., "A" 4.2 % Accenture PLC, "A" 3.5 % Aon PLC 2.5 % Salesforce, Inc. 2.4 % Church & Dwight Co., Inc. 2.4 % Agilent Technologies, Inc. 2.2 % | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.97% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total operating expenses do not exceed 0.97% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007249 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Blended Research® Core Equity Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Blended Research Core Equity Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.44 % | |
| Expenses Paid, Amount | $ 50 | |
| Expense Ratio, Percent | 0.44% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Blended Research Core Equity Portfolio (fund) provided a total return of 25.50 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 utilities, financials, communication services, and information technology sectors benefited relative performance. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within both the consumer staples and industrials sectors held back relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 25.50 % 15.15 % 12.32 % 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/ic | |
| Net Assets | $ 404,487,610 | |
| Holdings Count | Holding | 106 | |
| Advisory Fees Paid, Amount | $ 1,603,717 | [13] |
| Investment Company Portfolio Turnover | 40% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 404,487,610 Total Management Fee ($)#: 1,603,717 Total Number of Holdings: 106 Portfolio Turnover Rate (%): 40 # 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 99.4 % Money Market Funds 0.6 % Equity sectors Information Technology 31.2 % Financials 13.9 % Health Care 10.6 % Consumer Discretionary 10.4 % Communication Services 10.2 % Industrials 7.3 % Consumer Staples 5.5 % Utilities 3.1 % Energy 3.0 % Real Estate 2.9 % Materials 1.3 % Top ten holdings NVIDIA Corp. 7.9 % Apple, Inc. 7.0 % Microsoft Corp. 6.6 % Amazon.com, Inc. 4.8 % Meta Platforms, Inc., "A" 4.0 % Alphabet, Inc., "A" 2.6 % Visa, Inc., "A" 2.3 % AbbVie, Inc. 1.9 % Johnson & Johnson 1.7 % Alphabet, Inc., "C" 1.7 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings NVIDIA Corp. 7.9 % Apple, Inc. 7.0 % Microsoft Corp. 6.6 % Amazon.com, Inc. 4.8 % Meta Platforms, Inc., "A" 4.0 % Alphabet, Inc., "A" 2.6 % Visa, Inc., "A" 2.3 % AbbVie, Inc. 1.9 % Johnson & Johnson 1.7 % Alphabet, Inc., "C" 1.7 % | |
| C000007250 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Blended Research® Core Equity Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Blended Research Core Equity Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 0.69 % | |
| Expenses Paid, Amount | $ 78 | |
| Expense Ratio, Percent | 0.69% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Blended Research Core Equity Portfolio (fund) provided a total return of 25.18 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 utilities, financials, communication services, and information technology sectors benefited relative performance. Top detractors from performance relative to the Standard & Poor's 500 Stock Index: Stock selection within both the consumer staples and industrials sectors held back relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 25.18 % 14.86 % 12.04 % 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/sc | |
| Net Assets | $ 404,487,610 | |
| Holdings Count | Holding | 106 | |
| Advisory Fees Paid, Amount | $ 1,603,717 | [14] |
| Investment Company Portfolio Turnover | 40% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 404,487,610 Total Management Fee ($)#: 1,603,717 Total Number of Holdings: 106 Portfolio Turnover Rate (%): 40 # 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 99.4 % Money Market Funds 0.6 % Equity sectors Information Technology 31.2 % Financials 13.9 % Health Care 10.6 % Consumer Discretionary 10.4 % Communication Services 10.2 % Industrials 7.3 % Consumer Staples 5.5 % Utilities 3.1 % Energy 3.0 % Real Estate 2.9 % Materials 1.3 % Top ten holdings NVIDIA Corp. 7.9 % Apple, Inc. 7.0 % Microsoft Corp. 6.6 % Amazon.com, Inc. 4.8 % Meta Platforms, Inc., "A" 4.0 % Alphabet, Inc., "A" 2.6 % Visa, Inc., "A" 2.3 % AbbVie, Inc. 1.9 % Johnson & Johnson 1.7 % Alphabet, Inc., "C" 1.7 % MFS uses the Global Industry Classification Standard (GICS ® | |
| Largest Holdings [Text Block] | Top ten holdings NVIDIA Corp. 7.9 % Apple, Inc. 7.0 % Microsoft Corp. 6.6 % Amazon.com, Inc. 4.8 % Meta Platforms, Inc., "A" 4.0 % Alphabet, Inc., "A" 2.6 % Visa, Inc., "A" 2.3 % AbbVie, Inc. 1.9 % Johnson & Johnson 1.7 % Alphabet, Inc., "C" 1.7 % | |
| C000007255 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® U.S. Government Money Market Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS U.S. Government Money Market Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.45 % | |
| Expenses Paid, Amount | $ 46 | |
| Expense Ratio, Percent | 0.45% | |
| Net Assets | $ 273,619,492 | |
| Holdings Count | Holding | 21 | |
| Advisory Fees Paid, Amount | $ 1,068,642 | [15] |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 273,619,492 Total Management Fee ($)#: $ Total Number of Holdings: 21 # | |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 12/31/24) Portfolio structure U.S. Treasury and U.S. Government Agency Securities and Equivalents 71.0 % Repurchase Agreements, collateralized by U.S. Treasury and/or U.S. Government Agency Securities 29.0 % Composition including fixed income credit quality A-1+ 55.3 % A-1 44.7 % Maturity breakdown 0 - 7 days 35.3 % 8 - 29 days 17.5 % 30 - 59 days 28.3 % 60 - 89 days 12.4 % 90 - 365 days 6.5 % Ratings are assigned to portfolio securities utilizing ratings from Moody’s, Fitch, and Standard & Poor’s rating agencies and applying the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. Ratings are shown in the S&P scale. All ratings are subject to change. The fund did not hold unrated securities. The fund is not rated by these agencies. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned to portfolio securities utilizing ratings from Moody’s, Fitch, and Standard & Poor’s rating agencies and applying the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. Ratings are shown in the S&P scale. All ratings are subject to change. The fund did not hold unrated securities. The fund is not rated by these agencies. | |
| C000007256 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® U.S. Government Money Market Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS U.S. Government Money Market Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 0.45 % | |
| Expenses Paid, Amount | $ 46 | |
| Expense Ratio, Percent | 0.45% | |
| Net Assets | $ 273,619,492 | |
| Holdings Count | Holding | 21 | |
| Advisory Fees Paid, Amount | $ 1,068,642 | [16] |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 273,619,492 Total Management Fee ($)#: $ Total Number of Holdings: 21 # | |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 12/31/24) Portfolio structure U.S. Treasury and U.S. Government Agency Securities and Equivalents 71.0 % Repurchase Agreements, collateralized by U.S. Treasury and/or U.S. Government Agency Securities 29.0 % Composition including fixed income credit quality A-1+ 55.3 % A-1 44.7 % Maturity breakdown 0 - 7 days 35.3 % 8 - 29 days 17.5 % 30 - 59 days 28.3 % 60 - 89 days 12.4 % 90 - 365 days 6.5 % Ratings are assigned to portfolio securities utilizing ratings from Moody’s, Fitch, and Standard & Poor’s rating agencies and applying the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. Ratings are shown in the S&P scale. All ratings are subject to change. The fund did not hold unrated securities. The fund is not rated by these agencies. | |
| Credit Ratings Selection [Text Block] | Ratings are assigned to portfolio securities utilizing ratings from Moody’s, Fitch, and Standard & Poor’s rating agencies and applying the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. Ratings are shown in the S&P scale. All ratings are subject to change. The fund did not hold unrated securities. The fund is not rated by these agencies. | |
| C000007261 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Research International Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Research International Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.89 % | |
| Expenses Paid, Amount | $ 90 | |
| Expense Ratio, Percent | 0.89% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Research International Portfolio (fund) provided a total return of 3.09 3.82 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 MSCI EAFE Index: Stock selection within the energy sector contributed to relative performance. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, benefited relative performance. Top detractors from performance relative to the MSCI EAFE Index: Security selection within the health care and consumer cyclicals sectors detracted from 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 Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 3.09 % 3.89 % 5.21 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 3.82 % 4.73 % 5.20 % ∆ 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/ic | |
| Net Assets | $ 462,775,150 | |
| Holdings Count | Holding | 111 | |
| Advisory Fees Paid, Amount | $ 4,202,495 | [17] |
| Investment Company Portfolio Turnover | 22% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 462,775,150 Total Management Fee ($)#: 4,202,495 Total Number of Holdings: 111 Portfolio Turnover Rate (%): 22 # 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 97.0 % Money Market Funds 3.0 % Top ten holdings Schneider Electric SE 3.7 % Linde PLC 2.9 % Roche Holding AG 2.6 % Hitachi Ltd. 2.5 % Novo Nordisk A.S., "B" 2.4 % Nestle S.A. 2.0 % LVMH Moet Hennessy Louis Vuitton SE 2.0 % NatWest Group PLC 1.7 % Aon PLC 1.6 % ASML Holding N.V. 1.6 % Issuer country weightings Japan 19.2 % France 13.8 % United Kingdom 12.7 % United States 11.5 % Switzerland 7.9 % Germany 6.0 % Netherlands 4.8 % Australia 3.6 % Denmark 3.0 % Other Countries 17.5 % | |
| Largest Holdings [Text Block] | Top ten holdings Schneider Electric SE 3.7 % Linde PLC 2.9 % Roche Holding AG 2.6 % Hitachi Ltd. 2.5 % Novo Nordisk A.S., "B" 2.4 % Nestle S.A. 2.0 % LVMH Moet Hennessy Louis Vuitton SE 2.0 % NatWest Group PLC 1.7 % Aon PLC 1.6 % ASML Holding N.V. 1.6 % | |
| C000007262 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Research International Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Research International Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.14 % | |
| Expenses Paid, Amount | $ 116 | |
| Expense Ratio, Percent | 1.14% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Research International Portfolio (fund) provided a total return of 2.78 3.82 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 MSCI EAFE Index: Stock selection within the energy sector contributed to relative performance. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, benefited relative performance. Top detractors from performance relative to the MSCI EAFE Index: Security selection within the health care and consumer cyclicals sectors detracted from 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 Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 2.78 % 3.64 % 4.95 % Comparative Benchmark(s) MSCI EAFE (Europe, Australasia, Far East) Index (net div) ∆ 3.82 % 4.73 % 5.20 % ∆ 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/sc | |
| Net Assets | $ 462,775,150 | |
| Holdings Count | Holding | 111 | |
| Advisory Fees Paid, Amount | $ 4,202,495 | [18] |
| Investment Company Portfolio Turnover | 22% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 462,775,150 Total Management Fee ($)#: 4,202,495 Total Number of Holdings: 111 Portfolio Turnover Rate (%): 22 # 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 97.0 % Money Market Funds 3.0 % Top ten holdings Schneider Electric SE 3.7 % Linde PLC 2.9 % Roche Holding AG 2.6 % Hitachi Ltd. 2.5 % Novo Nordisk A.S., "B" 2.4 % Nestle S.A. 2.0 % LVMH Moet Hennessy Louis Vuitton SE 2.0 % NatWest Group PLC 1.7 % Aon PLC 1.6 % ASML Holding N.V. 1.6 % Issuer country weightings Japan 19.2 % France 13.8 % United Kingdom 12.7 % United States 11.5 % Switzerland 7.9 % Germany 6.0 % Netherlands 4.8 % Australia 3.6 % Denmark 3.0 % Other Countries 17.5 % | |
| Largest Holdings [Text Block] | Top ten holdings Schneider Electric SE 3.7 % Linde PLC 2.9 % Roche Holding AG 2.6 % Hitachi Ltd. 2.5 % Novo Nordisk A.S., "B" 2.4 % Nestle S.A. 2.0 % LVMH Moet Hennessy Louis Vuitton SE 2.0 % NatWest Group PLC 1.7 % Aon PLC 1.6 % ASML Holding N.V. 1.6 % | |
| C000007263 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Research Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Research Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.85 % | |
| Expenses Paid, Amount | $ 91 | |
| Expense Ratio, Percent | 0.85% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Global Research Portfolio (fund) provided a total return of 15.21 17.49 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 MSCI All Country World Index: Security selection within the technology sector contributed to relative performance. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within both the consumer cyclicals and energy sectors detracted from 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 Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 15.21 % 9.33 % 9.45 % Comparative Benchmark(s) MSCI All Country World Index (net div) ∆ 17.49 % 10.06 % 9.23 % ∆ 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/ic | |
| Net Assets | $ 75,163,746 | |
| Holdings Count | Holding | 135 | |
| Advisory Fees Paid, Amount | $ 566,666 | [19] |
| Investment Company Portfolio Turnover | 21% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 75,163,746 Total Management Fee ($)#: 566,666 Total Number of Holdings: 135 Portfolio Turnover Rate (%): 21 # 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 99.4 % Money Market Funds 0.6 % Top ten holdings Microsoft Corp. 4.9 % Amazon.com, Inc. 3.7 % NVIDIA Corp. 3.6 % Alphabet, Inc., "A" 3.5 % Visa, Inc., "A" 2.6 % Meta Platforms, Inc., "A" 2.5 % Taiwan Semiconductor Manufacturing Co. Ltd. 2.0 % Apple, Inc. 1.6 % Salesforce, Inc. 1.5 % Hitachi Ltd. 1.3 % Issuer country weightings United States 66.7 % France 5.0 % United Kingdom 4.7 % Japan 4.3 % Switzerland 3.4 % Taiwan 2.0 % Canada 1.9 % China 1.7 % Netherlands 1.5 % Other Countries 8.8 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 4.9 % Amazon.com, Inc. 3.7 % NVIDIA Corp. 3.6 % Alphabet, Inc., "A" 3.5 % Visa, Inc., "A" 2.6 % Meta Platforms, Inc., "A" 2.5 % Taiwan Semiconductor Manufacturing Co. Ltd. 2.0 % Apple, Inc. 1.6 % Salesforce, Inc. 1.5 % Hitachi Ltd. 1.3 % | |
| C000007264 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Research Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Research Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.10 % | |
| Expenses Paid, Amount | $ 118 | |
| Expense Ratio, Percent | 1.10% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Global Research Portfolio (fund) provided a total return of 14.95 17.49 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 MSCI All Country World Index: Security selection within the technology sector contributed to relative performance. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection within both the consumer cyclicals and energy sectors detracted from 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 Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 14.95 % 9.06 % 9.17 % Comparative Benchmark(s) MSCI All Country World Index (net div) ∆ 17.49 % 10.06 % 9.23 % ∆ 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/sc | |
| Net Assets | $ 75,163,746 | |
| Holdings Count | Holding | 135 | |
| Advisory Fees Paid, Amount | $ 566,666 | [20] |
| Investment Company Portfolio Turnover | 21% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 75,163,746 Total Management Fee ($)#: 566,666 Total Number of Holdings: 135 Portfolio Turnover Rate (%): 21 # 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 99.4 % Money Market Funds 0.6 % Top ten holdings Microsoft Corp. 4.9 % Amazon.com, Inc. 3.7 % NVIDIA Corp. 3.6 % Alphabet, Inc., "A" 3.5 % Visa, Inc., "A" 2.6 % Meta Platforms, Inc., "A" 2.5 % Taiwan Semiconductor Manufacturing Co. Ltd. 2.0 % Apple, Inc. 1.6 % Salesforce, Inc. 1.5 % Hitachi Ltd. 1.3 % Issuer country weightings United States 66.7 % France 5.0 % United Kingdom 4.7 % Japan 4.3 % Switzerland 3.4 % Taiwan 2.0 % Canada 1.9 % China 1.7 % Netherlands 1.5 % Other Countries 8.8 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 4.9 % Amazon.com, Inc. 3.7 % NVIDIA Corp. 3.6 % Alphabet, Inc., "A" 3.5 % Visa, Inc., "A" 2.6 % Meta Platforms, Inc., "A" 2.5 % Taiwan Semiconductor Manufacturing Co. Ltd. 2.0 % Apple, Inc. 1.6 % Salesforce, Inc. 1.5 % Hitachi Ltd. 1.3 % | |
| C000007267 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 ~ Initial Class $ 0.67 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses. | |
| Expenses Paid, Amount | $ 68 | [21] |
| Expense Ratio, Percent | 0.67% | [21] |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Income Portfolio (fund) provided a total return of 3.25 1.25 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 Bloomberg U.S. Aggregate Bond Index: The fund’s exposure to both the collateralized mortgage obligations (CMO) and municipal sectors, for which the benchmark has no exposure, supported relative performance. The combination of security selection and overweight allocations to both the industrials and financial institutions sectors also benefited relative returns. From a credit quality perspective, the fund’s out-of-benchmark exposure to non-investment grade bonds further strengthened relative results. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund's overweight allocation to AAA-rated credit issues detracted from relative performance. Security selection within the mortgage-backed securities (MBS) agency fixed rate sector also weakened relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 3.25 % 1.04 % 2.66 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.25 % (0.33 ) % 1.35 % ∆ 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/ic | |
| Net Assets | $ 35,109,822 | |
| Holdings Count | Holding | 212 | |
| Advisory Fees Paid, Amount | $ 164,892 | [22] |
| Investment Company Portfolio Turnover | 85% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 35,109,822 Average Effective Maturity (yrs): 8.5 Total Number of Holdings: 212 Average Effective Duration (yrs): 6.0 Total Management Fee ($)#: 164,892 Portfolio Turnover Rate (%): 85 # 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 Fixed Income 98.8 % Money Market Funds 1.2 % Composition including fixed income credit quality AAA 9.7 % AA 6.6 % A 12.5 % BBB 27.3 % BB 7.5 % B 4.5 % CCC 0.7 % C 0.0 % U.S. Government 26.5 % Federal Agencies 1.6 % Not Rated 1.9 % Money Market Funds 1.2 % 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. | |
| C000007268 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Income Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Income Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 ~ Service Class $ 0.92 % ˜ Expenses are direct expenses and do not include underlying fund fees and expenses. | |
| Expenses Paid, Amount | $ 93 | [23] |
| Expense Ratio, Percent | 0.92% | [23] |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Income Portfolio (fund) provided a total return of 2.91 1.25 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 Bloomberg U.S. Aggregate Bond Index: The fund’s exposure to both the collateralized mortgage obligations (CMO) and municipal sectors, for which the benchmark has no exposure, supported relative performance. The combination of security selection and overweight allocations to both the industrials and financial institutions sectors also benefited relative returns. From a credit quality perspective, the fund’s out-of-benchmark exposure to non-investment grade bonds further strengthened relative results. Top detractors from performance relative to the Bloomberg U.S. Aggregate Bond Index: The fund's overweight allocation to AAA-rated credit issues detracted from relative performance. Security selection within the mortgage-backed securities (MBS) agency fixed rate sector also weakened relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 2.91 % 0.78 % 2.41 % Comparative Benchmark(s) Bloomberg U.S. Aggregate Bond Index ∆ 1.25 % (0.33 ) % 1.35 % ∆ 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/sc | |
| Net Assets | $ 35,109,822 | |
| Holdings Count | Holding | 212 | |
| Advisory Fees Paid, Amount | $ 164,892 | [24] |
| Investment Company Portfolio Turnover | 85% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 35,109,822 Average Effective Maturity (yrs): 8.5 Total Number of Holdings: 212 Average Effective Duration (yrs): 6.0 Total Management Fee ($)#: 164,892 Portfolio Turnover Rate (%): 85 # 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 Fixed Income 98.8 % Money Market Funds 1.2 % Composition including fixed income credit quality AAA 9.7 % AA 6.6 % A 12.5 % BBB 27.3 % BB 7.5 % B 4.5 % CCC 0.7 % C 0.0 % U.S. Government 26.5 % Federal Agencies 1.6 % Not Rated 1.9 % Money Market Funds 1.2 % 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. | |
| C000007271 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Technology Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Technology Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.86 % | |
| Expenses Paid, Amount | $ 102 | |
| Expense Ratio, Percent | 0.86% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Technology Portfolio (fund) provided a total return of 36.80 25.02 36.08% 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 North American Technology Sector Index: Security selection within the software industry contributed to relative performance. An underweight allocation and, to a lesser extent, stock selection within the technology hardware, storage & peripherals industry further supported relative returns. Top detractors to performance relative to the Standard & Poor's North American Technology Sector Index: Security selection within the interactive media & services industry detracted from relative performance. The fund’s cash and/or cash equivalents position during the period also hurt relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class 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. | |
| 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. 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 Initial Class 36.80 % 17.76 % 18.03 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 25.02 % 14.53 % 13.10 % Standard & Poor's North American Technology Sector Index +∆ 36.08 % 21.06 % 20.70 % + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the Standard & Poor's North American Technology Sector Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Standard & Poor's North American Technology Sector Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the Standard & Poor's North American Technology Sector Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Standard & Poor's North American Technology Sector Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 180,795,051 | |
| Holdings Count | Holding | 58 | |
| Advisory Fees Paid, Amount | $ 1,197,542 | [25] |
| Investment Company Portfolio Turnover | 47% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 180,795,051 Total Management Fee ($)#: 1,197,542 Total Number of Holdings: 58 Portfolio Turnover Rate (%): 47 # 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 97.5 % Money Market Funds 2.5 % Top ten holdings Meta Platforms, Inc., "A" 10.1 % Alphabet, Inc., "A" 8.0 % NVIDIA Corp. 7.6 % Microsoft Corp. 7.4 % Apple, Inc. 6.2 % Broadcom, Inc. 4.2 % Salesforce, Inc. 3.6 % Oracle Corp. 3.0 % ServiceNow, Inc. 2.9 % Accenture PLC, "A" 2.4 % Top five industries Computer Software 29.4 % Electronics 21.6 % Internet 20.9 % Computer Software - Systems 16.8 % Business Services 5.4 % For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). | |
| Largest Holdings [Text Block] | Top ten holdings Meta Platforms, Inc., "A" 10.1 % Alphabet, Inc., "A" 8.0 % NVIDIA Corp. 7.6 % Microsoft Corp. 7.4 % Apple, Inc. 6.2 % Broadcom, Inc. 4.2 % Salesforce, Inc. 3.6 % Oracle Corp. 3.0 % ServiceNow, Inc. 2.9 % Accenture PLC, "A" 2.4 % | |
| C000007272 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Technology Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Technology Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.11 % | |
| Expenses Paid, Amount | $ 131 | |
| Expense Ratio, Percent | 1.11% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Technology Portfolio (fund) provided a total return of 36.45 25.02 36.08% 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 North American Technology Sector Index: Security selection within the software industry contributed to relative performance. An underweight allocation and, to a lesser extent, stock selection within the technology hardware, storage & peripherals industry further supported relative returns. Top detractors to performance relative to the Standard & Poor's North American Technology Sector Index: Security selection within the interactive media & services industry detracted from relative performance. The fund’s cash and/or cash equivalents position during the period also hurt relative results. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class 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. | |
| 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. 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 Service Class 36.45 % 17.46 % 17.75 % Comparative Benchmark(s) Standard & Poor's 500 Stock Index +∆ 25.02 % 14.53 % 13.10 % Standard & Poor's North American Technology Sector Index +∆ 36.08 % 21.06 % 20.70 % + Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the Standard & Poor's North American Technology Sector Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Standard & Poor's North American Technology Sector Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Standard & Poor's 500 Stock Index replaced the Standard & Poor's North American Technology Sector Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Standard & Poor's North American Technology Sector Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 180,795,051 | |
| Holdings Count | Holding | 58 | |
| Advisory Fees Paid, Amount | $ 1,197,542 | [26] |
| Investment Company Portfolio Turnover | 47% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 180,795,051 Total Management Fee ($)#: 1,197,542 Total Number of Holdings: 58 Portfolio Turnover Rate (%): 47 # 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 97.5 % Money Market Funds 2.5 % Top ten holdings Meta Platforms, Inc., "A" 10.1 % Alphabet, Inc., "A" 8.0 % NVIDIA Corp. 7.6 % Microsoft Corp. 7.4 % Apple, Inc. 6.2 % Broadcom, Inc. 4.2 % Salesforce, Inc. 3.6 % Oracle Corp. 3.0 % ServiceNow, Inc. 2.9 % Accenture PLC, "A" 2.4 % Top five industries Computer Software 29.4 % Electronics 21.6 % Internet 20.9 % Computer Software - Systems 16.8 % Business Services 5.4 % For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). | |
| Largest Holdings [Text Block] | Top ten holdings Meta Platforms, Inc., "A" 10.1 % Alphabet, Inc., "A" 8.0 % NVIDIA Corp. 7.6 % Microsoft Corp. 7.4 % Apple, Inc. 6.2 % Broadcom, Inc. 4.2 % Salesforce, Inc. 3.6 % Oracle Corp. 3.0 % ServiceNow, Inc. 2.9 % Accenture PLC, "A" 2.4 % | |
| C000007281 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Core Equity Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Core Equity Portfolio 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 insurancefunds.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 | insurancefunds.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 Initial Class $ 0.80 % | |
| Expenses Paid, Amount | $ 88 | |
| Expense Ratio, Percent | 0.80% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Core Equity Portfolio (fund) provided a total return of 20.11 23.81 ® 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 Russell 3000 ® Security selection within both the health care and energy sectors benefited relative performance. Top detractors from performance relative to the Russell 3000 ® Stock selection within the technology, capital goods, and consumer cyclicals 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 Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 20.11 % 12.73 % 12.46 % Comparative Benchmark(s) Russell 3000 ® 23.81 % 13.86 % 12.55 % ∆ 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/ic | |
| Net Assets | $ 283,158,336 | |
| Holdings Count | Holding | 185 | |
| Advisory Fees Paid, Amount | $ 2,040,723 | [27] |
| Investment Company Portfolio Turnover | 33% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 283,158,336 Total Management Fee ($)#: 2,040,723 Total Number of Holdings: 185 Portfolio Turnover Rate (%): 33 # 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 99.6 % Money Market Funds 0.5 % Securities Sold Short (0.1 ) % Global equity sectors Technology 37.6 % Financial Services 14.3 % Consumer Cyclicals 13.0 % Capital Goods 12.4 % Health Care 11.0 % Energy 6.1 % Consumer Staples 3.4 % Telecommunications and Cable Television 1.7 % Top ten holdings Microsoft Corp. 6.8 % Amazon.com, Inc. 5.1 % NVIDIA Corp. 4.6 % Alphabet, Inc., "A" 3.7 % Apple, Inc. 2.9 % Meta Platforms, Inc., "A" 2.5 % JPMorgan Chase & Co. 1.9 % Visa, Inc., "A" 1.8 % Marvell Technology, Inc. 1.6 % Johnson & Johnson 1.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 6.8 % Amazon.com, Inc. 5.1 % NVIDIA Corp. 4.6 % Alphabet, Inc., "A" 3.7 % Apple, Inc. 2.9 % Meta Platforms, Inc., "A" 2.5 % JPMorgan Chase & Co. 1.9 % Visa, Inc., "A" 1.8 % Marvell Technology, Inc. 1.6 % Johnson & Johnson 1.4 % | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as short sale dividend and interest expenses incurred in connection with the fund’s investment activity), such that total operating expenses do not exceed 0.78% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Initial Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as short sale dividend and interest expenses incurred in connection with the fund’s investment activity), such that total operating expenses do not exceed 0.78% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007282 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Core Equity Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Core Equity Portfolio 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 insurancefunds.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 | insurancefunds.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 Service Class $ 1.05 % | |
| Expenses Paid, Amount | $ 115 | |
| Expense Ratio, Percent | 1.05% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Core Equity Portfolio (fund) provided a total return of 19.87 23.81 ® 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 Russell 3000 ® Security selection within both the health care and energy sectors benefited relative performance. Top detractors from performance relative to the Russell 3000 ® Stock selection within the technology, capital goods, and consumer cyclicals 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 Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 19.87 % 12.45 % 12.18 % Comparative Benchmark(s) Russell 3000 ® 23.81 % 13.86 % 12.55 % ∆ 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/sc | |
| Net Assets | $ 283,158,336 | |
| Holdings Count | Holding | 185 | |
| Advisory Fees Paid, Amount | $ 2,040,723 | [28] |
| Investment Company Portfolio Turnover | 33% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 283,158,336 Total Management Fee ($)#: 2,040,723 Total Number of Holdings: 185 Portfolio Turnover Rate (%): 33 # 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 99.6 % Money Market Funds 0.5 % Securities Sold Short (0.1 ) % Global equity sectors Technology 37.6 % Financial Services 14.3 % Consumer Cyclicals 13.0 % Capital Goods 12.4 % Health Care 11.0 % Energy 6.1 % Consumer Staples 3.4 % Telecommunications and Cable Television 1.7 % Top ten holdings Microsoft Corp. 6.8 % Amazon.com, Inc. 5.1 % NVIDIA Corp. 4.6 % Alphabet, Inc., "A" 3.7 % Apple, Inc. 2.9 % Meta Platforms, Inc., "A" 2.5 % JPMorgan Chase & Co. 1.9 % Visa, Inc., "A" 1.8 % Marvell Technology, Inc. 1.6 % Johnson & Johnson 1.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 6.8 % Amazon.com, Inc. 5.1 % NVIDIA Corp. 4.6 % Alphabet, Inc., "A" 3.7 % Apple, Inc. 2.9 % Meta Platforms, Inc., "A" 2.5 % JPMorgan Chase & Co. 1.9 % Visa, Inc., "A" 1.8 % Marvell Technology, Inc. 1.6 % Johnson & Johnson 1.4 % | |
| Material Fund Change [Text Block] | MATERIAL FUND CHANGES This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as short sale dividend and interest expenses incurred in connection with the fund’s investment activity), such that total operating expenses do not exceed 1.03% annually of the class’s average daily net assets. This written agreement will continue until modified by the fund’s Board Trustees, but such agreement will continue at least until April 30, 2026. | |
| Material Fund Change Expenses [Text Block] | Effective August 1, 2024, for Service Class shares, the investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as short sale dividend and interest expenses incurred in connection with the fund’s investment activity), such that total operating expenses do not exceed 1.03% annually of the class’s average daily net assets. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the fund since January 1, 2024. For more complete information, you may review the fund's next prospectus, which we expect to be available on April 30, 2025 at insurancefunds.mfs.com | |
| Updated Prospectus Phone Number | 1‑800‑225‑2606 | |
| Updated Prospectus Web Address | insurancefunds.mfs.com | |
| C000007285 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Emerging Markets Equity Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Emerging Markets Equity Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 1.23 % | |
| Expenses Paid, Amount | $ 130 | |
| Expense Ratio, Percent | 1.23% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Emerging Markets Equity Portfolio (fund) provided a total return of 11.61 7.50 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 MSCI Emerging Markets Index: Security selection within the information technology, communication services, health care, consumer discretionary, and energy sectors contributed to relative performance. An underweight allocation to the materials sector also supported relative results. Top detractors from performance relative to the MSCI Emerging Markets Index: An overweight position in the consumer staples sector detracted from 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 Initial Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Initial Class 11.61 % 0.49 % 3.40 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 7.50 % 1.70 % 3.64 % ∆ 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/ic | |
| Net Assets | $ 34,718,552 | |
| Holdings Count | Holding | 99 | |
| Advisory Fees Paid, Amount | $ 373,791 | [29] |
| Investment Company Portfolio Turnover | 35% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 34,718,552 Total Management Fee ($)#: 373,791 Total Number of Holdings: 99 Portfolio Turnover Rate (%): 35 # 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 98.0 % Money Market Funds 2.0 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.9 % Tencent Holdings Ltd. 6.2 % Samsung Electronics Co. Ltd. 3.6 % Alibaba Group Holding Ltd. 3.2 % Infosys Ltd. 2.6 % China Construction Bank Corp. 2.2 % Tata Consultancy Services Ltd. 2.0 % HDFC Bank Ltd. 2.0 % Delta Electronics, Inc. 1.9 % Ping An Insurance Co. of China Ltd., "H" 1.8 % Issuer country weightings China 27.2 % India 15.8 % Taiwan 15.3 % South Korea 11.2 % Brazil 5.1 % Indonesia 3.5 % Mexico 2.9 % United States 2.3 % Thailand 2.3 % Other Countries 14.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.9 % Tencent Holdings Ltd. 6.2 % Samsung Electronics Co. Ltd. 3.6 % Alibaba Group Holding Ltd. 3.2 % Infosys Ltd. 2.6 % China Construction Bank Corp. 2.2 % Tata Consultancy Services Ltd. 2.0 % HDFC Bank Ltd. 2.0 % Delta Electronics, Inc. 1.9 % Ping An Insurance Co. of China Ltd., "H" 1.8 % | |
| C000007286 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Emerging Markets Equity Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Emerging Markets Equity Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 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 December 31, 2024, Service Class shares of the MFS Emerging Markets Equity Portfolio (fund) provided a total return of 11.31 7.50 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 MSCI Emerging Markets Index: Security selection within the information technology, communication services, health care, consumer discretionary, and energy sectors contributed to relative performance. An underweight allocation to the materials sector also supported relative results. Top detractors from performance relative to the MSCI Emerging Markets Index: An overweight position in the consumer staples sector detracted from 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 Service Class over a ten year period or since inception, if shorter, in comparison to a broad measure of market performance. | |
| 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. 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 Service Class 11.31 % 0.24 % 3.14 % Comparative Benchmark(s) MSCI Emerging Markets Index (net div) ∆ 7.50 % 1.70 % 3.64 % ∆ 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/sc | |
| Net Assets | $ 34,718,552 | |
| Holdings Count | Holding | 99 | |
| Advisory Fees Paid, Amount | $ 373,791 | [30] |
| Investment Company Portfolio Turnover | 35% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 34,718,552 Total Management Fee ($)#: 373,791 Total Number of Holdings: 99 Portfolio Turnover Rate (%): 35 # 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 98.0 % Money Market Funds 2.0 % Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.9 % Tencent Holdings Ltd. 6.2 % Samsung Electronics Co. Ltd. 3.6 % Alibaba Group Holding Ltd. 3.2 % Infosys Ltd. 2.6 % China Construction Bank Corp. 2.2 % Tata Consultancy Services Ltd. 2.0 % HDFC Bank Ltd. 2.0 % Delta Electronics, Inc. 1.9 % Ping An Insurance Co. of China Ltd., "H" 1.8 % Issuer country weightings China 27.2 % India 15.8 % Taiwan 15.3 % South Korea 11.2 % Brazil 5.1 % Indonesia 3.5 % Mexico 2.9 % United States 2.3 % Thailand 2.3 % Other Countries 14.4 % | |
| Largest Holdings [Text Block] | Top ten holdings Taiwan Semiconductor Manufacturing Co. Ltd. 9.9 % Tencent Holdings Ltd. 6.2 % Samsung Electronics Co. Ltd. 3.6 % Alibaba Group Holding Ltd. 3.2 % Infosys Ltd. 2.6 % China Construction Bank Corp. 2.2 % Tata Consultancy Services Ltd. 2.0 % HDFC Bank Ltd. 2.0 % Delta Electronics, Inc. 1.9 % Ping An Insurance Co. of China Ltd., "H" 1.8 % | |
| C000007287 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Governments Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Governments Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.70 % | |
| Expenses Paid, Amount | $ 68 | |
| Expense Ratio, Percent | 0.70% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Global Governments Portfolio (fund) provided a total return of ‑4.54%, at net asset value. This compares with a return of ‑1.69% for the fund’s benchmark, the Bloomberg Global Aggregate Index. The fund's other benchmark, the JPMorgan Global Government Bond Index (Unhedged), generated a return of ‑3.65%. 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 JPMorgan Global Government Bond Index: The fund’s overweight allocation to Italian securities, and underweight allocation to French-issued securities, contributed to relative performance. Favorable bond selection within Spain and the US also strengthened relative results. Top detractors from performance relative to the JPMorgan Global Government Bond Index: The fund's longer duration stance, particularly along the Mexican, Australian, and Great Britain yield curves, held back relative performance. Additionally, the fund's foreign exchange allocation decisions, most notably from its overweight exposure to developed market currencies, including the Japanese Yen and Norwegian Krone, further weakened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Initial Class 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. | |
| 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. 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 Initial Class (4.54 ) % (3.71 ) % (1.07 ) % Comparative Benchmark(s) Bloomberg Global Aggregate Index +∆ (1.69 ) % (1.96 ) % 0.15 % JPMorgan Global Government Bond Index (Unhedged) +∆ (3.65 ) % (3.18 ) % (0.54 ) % + Effective May 1, 2024, the Bloomberg Global Aggregate Index replaced the JPMorgan Global Government Bond Index (Unhedged) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the JPMorgan Global Government Bond Index (Unhedged) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg Global Aggregate Index replaced the JPMorgan Global Government Bond Index (Unhedged) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the JPMorgan Global Government Bond Index (Unhedged) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 83,389,940 | |
| Holdings Count | Holding | 71 | |
| Advisory Fees Paid, Amount | $ 644,818 | [31] |
| Investment Company Portfolio Turnover | 93% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 83,389,940 Average Effective Maturity (yrs): 9.5 Total Number of Holdings: 71 Average Effective Duration (yrs): 7.4 Total Management Fee ($)#: 644,818 Portfolio Turnover Rate (%): 93 # 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 Fixed Income 95.5 % Money Market Funds 4.5 % Issuer country weightings United States 49.0 % Japan 11.0 % Italy 10.6 % Germany 4.5 % United Kingdom 3.8 % Spain 3.6 % Greece 2.7 % Canada 2.5 % South Korea 2.3 % Other Countries 10.0 % Composition including fixed income credit quality AAA 10.2 % AA 7.4 % A 10.7 % BBB 15.4 % BB 0.7 % U.S. Government 41.9 % Federal Agencies 1.6 % Not Rated 7.6 % Money Market Funds 4.5 % 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. | |
| C000007288 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Governments Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Governments Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 0.95 % | |
| Expenses Paid, Amount | $ 93 | |
| Expense Ratio, Percent | 0.95% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Global Governments Portfolio (fund) provided a total return of ‑4.76%, at net asset value. This compares with a return of ‑1.69% for the fund’s benchmark, the Bloomberg Global Aggregate Index. The fund's other benchmark, the JPMorgan Global Government Bond Index (Unhedged), generated a return of ‑3.65%. 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 JPMorgan Global Government Bond Index: The fund’s overweight allocation to Italian securities, and underweight allocation to French-issued securities, contributed to relative performance. Favorable bond selection within Spain and the US also strengthened relative results. Top detractors from performance relative to the JPMorgan Global Government Bond Index: The fund's longer duration stance, particularly along the Mexican, Australian, and Great Britain yield curves, held back relative performance. Additionally, the fund's foreign exchange allocation decisions, most notably from its overweight exposure to developed market currencies, including the Japanese Yen and Norwegian Krone, further weakened relative returns. | |
| Performance Past Does Not Indicate Future [Text] | The fund’s past performance is not a good predictor of the fund’s future performance. | |
| Line Graph [Table Text Block] | FUND PERFORMANCE The fund’s past performance is not a good predictor of the fund’s future performance. Growth of a Hypothetical $10,000 Investment This graph shows the performance of a hypothetical $10,000 investment in Service Class 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. | |
| 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. 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 Service Class (4.76 ) % (3.95 ) % (1.32 ) % Comparative Benchmark(s) Bloomberg Global Aggregate Index +∆ (1.69 ) % (1.96 ) % 0.15 % JPMorgan Global Government Bond Index (Unhedged) +∆ (3.65 ) % (3.18 ) % (0.54 ) % + Effective May 1, 2024, the Bloomberg Global Aggregate Index replaced the JPMorgan Global Government Bond Index (Unhedged) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the JPMorgan Global Government Bond Index (Unhedged) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. ∆ Source: FactSet Research Systems Inc. | |
| No Deduction of Taxes [Text Block] | The graph and table below do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares. | |
| Performance Table Market Index Changed [Text Block] | Effective May 1, 2024, the Bloomberg Global Aggregate Index replaced the JPMorgan Global Government Bond Index (Unhedged) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the JPMorgan Global Government Bond Index (Unhedged) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 83,389,940 | |
| Holdings Count | Holding | 71 | |
| Advisory Fees Paid, Amount | $ 644,818 | [32] |
| Investment Company Portfolio Turnover | 93% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 83,389,940 Average Effective Maturity (yrs): 9.5 Total Number of Holdings: 71 Average Effective Duration (yrs): 7.4 Total Management Fee ($)#: 644,818 Portfolio Turnover Rate (%): 93 # 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 Fixed Income 95.5 % Money Market Funds 4.5 % Issuer country weightings United States 49.0 % Japan 11.0 % Italy 10.6 % Germany 4.5 % United Kingdom 3.8 % Spain 3.6 % Greece 2.7 % Canada 2.5 % South Korea 2.3 % Other Countries 10.0 % Composition including fixed income credit quality AAA 10.2 % AA 7.4 % A 10.7 % BBB 15.4 % BB 0.7 % U.S. Government 41.9 % Federal Agencies 1.6 % Not Rated 7.6 % Money Market Funds 4.5 % 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. | |
| C000007289 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.88 % | |
| Expenses Paid, Amount | $ 93 | |
| Expense Ratio, Percent | 0.88% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Global Growth Portfolio (fund) provided a total return of 11.07 17.49 24.23% 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 MSCI All Country World Index: An underweight allocation to the materials sector aided relative performance. In addition, not owning any stocks within the energy sector supported relative returns. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection in the consumer discretionary, consumer staples, communication services and information technology 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 Initial Class 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. | |
| 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. 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 Initial Class 11.07 % 9.24 % 10.76 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 17.49 % 10.06 % 9.23 % MSCI All Country World Growth Index (net div) +∆ 24.23 % 13.07 % 11.88 % + Effective March 1, 2024, the MSCI All Country World Index (net div) replaced the MSCI All Country World Growth Index (net div) because MFS believes the MSCI All Country World Index (net div) better reflects MFS’ implementation of fund’s investment strategy. ∆ 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 (net div) replaced the MSCI All Country World Growth Index (net div) because MFS believes the MSCI All Country World Index (net div) better reflects MFS’ implementation of fund’s investment strategy. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/ic | |
| Net Assets | $ 51,158,181 | |
| Holdings Count | Holding | 73 | |
| Advisory Fees Paid, Amount | $ 462,926 | [33] |
| Investment Company Portfolio Turnover | 21% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 51,158,181 Total Management Fee ($)#: 462,926 Total Number of Holdings: 73 Portfolio Turnover Rate (%): 21 # 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 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 6.4 % Visa, Inc., "A" 4.0 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.3 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.9 % Apple, Inc. 2.4 % Salesforce, Inc. 2.3 % Tencent Holdings Ltd. 2.3 % HDFC Bank Ltd. 2.2 % Agilent Technologies, Inc. 2.1 % Issuer country weightings United States 71.6 % Canada 5.2 % France 4.4 % China 3.8 % Taiwan 3.3 % Japan 2.4 % India 2.3 % Switzerland 1.7 % South Korea 1.3 % Other Countries 4.0 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 6.4 % Visa, Inc., "A" 4.0 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.3 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.9 % Apple, Inc. 2.4 % Salesforce, Inc. 2.3 % Tencent Holdings Ltd. 2.3 % HDFC Bank Ltd. 2.2 % Agilent Technologies, Inc. 2.1 % | |
| C000007290 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Growth Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Growth Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.13 % | |
| Expenses Paid, Amount | $ 119 | |
| Expense Ratio, Percent | 1.13% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Global Growth Portfolio (fund) provided a total return of 10.78 17.49 24.23% 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 MSCI All Country World Index: An underweight allocation to the materials sector aided relative performance. In addition, not owning any stocks within the energy sector supported relative returns. During the reporting period, the fund's relative currency exposure, resulting primarily from differences between the fund's and the benchmark's exposures to holdings of securities denominated in foreign currencies, was another contributor to relative performance. Top detractors from performance relative to the MSCI All Country World Index: Security selection in the consumer discretionary, consumer staples, communication services and information technology 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 Service Class 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. | |
| 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. 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 Service Class 10.78 % 8.97 % 10.48 % Comparative Benchmark(s) MSCI All Country World Index (net div) +∆ 17.49 % 10.06 % 9.23 % MSCI All Country World Growth Index (net div) +∆ 24.23 % 13.07 % 11.88 % + Effective March 1, 2024, the MSCI All Country World Index (net div) replaced the MSCI All Country World Growth Index (net div) because MFS believes the MSCI All Country World Index (net div) better reflects MFS’ implementation of fund’s investment strategy. ∆ 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 (net div) replaced the MSCI All Country World Growth Index (net div) because MFS believes the MSCI All Country World Index (net div) better reflects MFS’ implementation of fund’s investment strategy. | |
| Updated Performance Information Location [Text Block] | Visit mfs.com/perf/sc | |
| Net Assets | $ 51,158,181 | |
| Holdings Count | Holding | 73 | |
| Advisory Fees Paid, Amount | $ 462,926 | [34] |
| Investment Company Portfolio Turnover | 21% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 51,158,181 Total Management Fee ($)#: 462,926 Total Number of Holdings: 73 Portfolio Turnover Rate (%): 21 # 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 98.9 % Money Market Funds 1.1 % Top ten holdings Microsoft Corp. 6.4 % Visa, Inc., "A" 4.0 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.3 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.9 % Apple, Inc. 2.4 % Salesforce, Inc. 2.3 % Tencent Holdings Ltd. 2.3 % HDFC Bank Ltd. 2.2 % Agilent Technologies, Inc. 2.1 % Issuer country weightings United States 71.6 % Canada 5.2 % France 4.4 % China 3.8 % Taiwan 3.3 % Japan 2.4 % India 2.3 % Switzerland 1.7 % South Korea 1.3 % Other Countries 4.0 % | |
| Largest Holdings [Text Block] | Top ten holdings Microsoft Corp. 6.4 % Visa, Inc., "A" 4.0 % Taiwan Semiconductor Manufacturing Co. Ltd., ADR 3.3 % NVIDIA Corp. 3.1 % Accenture PLC, "A" 2.9 % Apple, Inc. 2.4 % Salesforce, Inc. 2.3 % Tencent Holdings Ltd. 2.3 % HDFC Bank Ltd. 2.2 % Agilent Technologies, Inc. 2.1 % | |
| C000007291 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Tactical Allocation Portfolio | |
| Class Name | Initial Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Tactical Allocation Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Initial Class $ 0.78 % | |
| Expenses Paid, Amount | $ 80 | |
| Expense Ratio, Percent | 0.78% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Initial Class shares of the MFS Global Tactical Allocation Portfolio (fund) provided a total return of 5.00 7.99 The fund’s investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from a combination of (1) individual security selection of a combination of debt instruments and equity securities and (2) a tactical asset allocation overlay primarily using derivative instruments to manage the fund’s exposure to asset classes (e.g. equity and fixed income), markets (e.g. U.S. and foreign countries), and currencies (e.g. U.S. dollar and Japanese yen). Derivatives include futures, forward contracts, options, swaps and certain complex structured securities. 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 MFS Global Tactical Allocation Blended Index: Within the equity portion of the fund, the combination of an overweight position and stock selection within the financials sector supported relative performance. Within the fixed income portion of the fund, an overweight exposure and bond selection within both the industrials and financial institutions sectors, and an underweight allocation to the treasury sector, benefited relative results. From a credit quality perspective, bond selection within BBB-rated securities, and the fund's exposure to BB-rated bonds, for which the benchmark has no exposure, also supported relative returns. The fund's yield curve positioning, particularly to the USD yield curve, was another area of relative strength. Within the fund’s tactical overlay, long exposures to the South Korean and Canadian equity markets, and a short exposure to the Australian equity market, via holdings of equity index futures, contributed to relative performance. The fund's lesser exposure to the long end of the yield curve, via holdings of interest rate swaps, also supported relative returns. From a currency perspective, the fund's short exposure to the euro further boosted relative results. Top detractors from performance relative to the MFS Global Tactical Allocation Blended Index: Within the equity portion of the fund, stock selection and an underweight position in the information technology sector held back relative performance. Security selection within both the communication services and consumer discretionary sectors also weighed on relative results. There were no factors within the fixed income portion of the fund that materially detracted from relative performance. Within the fund’s tactical overlay, long exposures to the Mexican and Spanish equity markets, via holdings of equity index futures, and a greater exposure to the short end of the yield curve, hurt relative returns. From a currency perspective, the fund's greater exposures to both the Norwegian and Swedish krona further dampened 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 Initial Class 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. | |
| 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. 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 Initial Class 5.00 % 3.13 % 3.92 % Comparative Benchmark(s) Bloomberg Global Aggregate Index ∆ (1.69 ) % (1.96 ) % 0.15 % MFS Global Tactical Allocation Blended Index ∆ 7.99 % 4.10 % 4.74 % ∆ 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/ic | |
| Net Assets | $ 342,456,614 | |
| Holdings Count | Holding | 1,004 | |
| Advisory Fees Paid, Amount | $ 2,659,448 | [35] |
| Investment Company Portfolio Turnover | 97% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 342,456,614 Total Management Fee ($)#: 2,659,448 Total Number of Holdings: 1,004 Portfolio Turnover Rate (%): 97 # | |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 12/31/24) Portfolio Structure Tactical Overlay (b) Active Security Selection (a) Long Short Net Market Exposure (c) Fixed Income U.S. 33.0 % 46.9 % (18.5 ) % 61.4 % Emerging Markets 14.3 % 0.0 % 0.0 % 14.3 % United Kingdom 3.5 % 3.6 % 0.0 % 7.1 % Asia/Pacific ex-Japan 1.5 % 4.7 % 0.0 % 6.2 % Europe ex-U.K. 10.3 % 0.0 % (4.6 ) % 5.7 % Japan 4.7 % 0.5 % 0.0 % 5.2 % North America ex-U.S. 4.4 % 0.0 % (1.1 ) % 3.3 % Supranational 1.5 % 0.0 % 0.0 % 1.5 % Total 73.2 % 55.7 % (24.2 ) % 104.7 % Equity Europe ex-U.K. 6.3 % 8.1 % (1.3 ) % 13.1 % U.S. Large Cap 11.6 % 0.1 % (2.3 ) % 9.4 % U.S. Small/Mid Cap 7.4 % 0.0 % (2.0 ) % 5.4 % Emerging Markets 1.9 % 7.1 % (5.3 ) % 3.7 % North America ex-U.S. 0.8 % 2.7 % 0.0 % 3.5 % United Kingdom 2.9 % 0.0 % (0.2 ) % 2.7 % Japan 2.4 % 0.0 % (1.8 ) % 0.6 % Asia/Pacific ex-Japan 0.6 % 1.6 % (2.5 ) % (0.3 ) % Total 33.9 % 19.6 % (15.4 ) % 38.1 % Real Estate-related U.S. 0.7 % 0.0 % 0.0 % 0.7 % Non-U.S. 0.3 % 0.0 % 0.0 % 0.3 % Total 1.0 % 0.0 % 0.0 % 1.0 % Fixed Income (Inflation-adjusted) U.S. 0.7 % 0.0 % 0.0 % 0.7 % Cash Cash & Cash Equivalents (d) 1.9 % Other (e) (46.4 ) % Total Net Exposure Summary 100.0 % (a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio. | |
| Exposure Basis Explanation [Text Block] | (a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio. | |
| C000007292 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | MFS® Global Tactical Allocation Portfolio | |
| Class Name | Service Class | |
| No Trading Symbol Flag | true | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about MFS Global Tactical Allocation Portfolio 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 insurancefunds.mfs.com | |
| Additional Information Phone Number | 1‑800‑225‑2606 | |
| Additional Information Email | orderliterature@mfs.com | |
| Additional Information Website | insurancefunds.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 Service Class $ 1.03 % | |
| Expenses Paid, Amount | $ 105 | |
| Expense Ratio, Percent | 1.03% | |
| Factors Affecting Performance [Text Block] | MANAGEMENT'S DISCUSSION OF FUND PERFORMANCE For the twelve months ended December 31, 2024, Service Class shares of the MFS Global Tactical Allocation Portfolio (fund) provided a total return of 4.68 7.99 The fund’s investment objective is to seek total return. MFS seeks to achieve the fund’s objective by generating returns from a combination of (1) individual security selection of a combination of debt instruments and equity securities and (2) a tactical asset allocation overlay primarily using derivative instruments to manage the fund’s exposure to asset classes (e.g. equity and fixed income), markets (e.g. U.S. and foreign countries), and currencies (e.g. U.S. dollar and Japanese yen). Derivatives include futures, forward contracts, options, swaps and certain complex structured securities. 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 MFS Global Tactical Allocation Blended Index: Within the equity portion of the fund, the combination of an overweight position and stock selection within the financials sector supported relative performance. Within the fixed income portion of the fund, an overweight exposure and bond selection within both the industrials and financial institutions sectors, and an underweight allocation to the treasury sector, benefited relative results. From a credit quality perspective, bond selection within BBB-rated securities, and the fund's exposure to BB-rated bonds, for which the benchmark has no exposure, also supported relative returns. The fund's yield curve positioning, particularly to the USD yield curve, was another area of relative strength. Within the fund’s tactical overlay, long exposures to the South Korean and Canadian equity markets, and a short exposure to the Australian equity market, via holdings of equity index futures, contributed to relative performance. The fund's lesser exposure to the long end of the yield curve, via holdings of interest rate swaps, also supported relative returns. From a currency perspective, the fund's short exposure to the euro further boosted relative results. Top detractors from performance relative to the MFS Global Tactical Allocation Blended Index: Within the equity portion of the fund, stock selection and an underweight position in the information technology sector held back relative performance. Security selection within both the communication services and consumer discretionary sectors also weighed on relative results. There were no factors within the fixed income portion of the fund that materially detracted from relative performance. Within the fund’s tactical overlay, long exposures to the Mexican and Spanish equity markets, via holdings of equity index futures, and a greater exposure to the short end of the yield curve, hurt relative returns. From a currency perspective, the fund's greater exposures to both the Norwegian and Swedish krona further dampened 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 Service Class 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. | |
| 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. 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 Service Class 4.68 % 2.87 % 3.66 % Comparative Benchmark(s) Bloomberg Global Aggregate Index ∆ (1.69 ) % (1.96 ) % 0.15 % MFS Global Tactical Allocation Blended Index ∆ 7.99 % 4.10 % 4.74 % ∆ 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/sc | |
| Net Assets | $ 342,456,614 | |
| Holdings Count | Holding | 1,004 | |
| Advisory Fees Paid, Amount | $ 2,659,448 | [36] |
| Investment Company Portfolio Turnover | 97% | |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 12/31/24 Net Assets ($): 342,456,614 Total Management Fee ($)#: 2,659,448 Total Number of Holdings: 1,004 Portfolio Turnover Rate (%): 97 # | |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL NET ASSETS AS OF 12/31/24) Portfolio Structure Tactical Overlay (b) Active Security Selection (a) Long Short Net Market Exposure (c) Fixed Income U.S. 33.0 % 46.9 % (18.5 ) % 61.4 % Emerging Markets 14.3 % 0.0 % 0.0 % 14.3 % United Kingdom 3.5 % 3.6 % 0.0 % 7.1 % Asia/Pacific ex-Japan 1.5 % 4.7 % 0.0 % 6.2 % Europe ex-U.K. 10.3 % 0.0 % (4.6 ) % 5.7 % Japan 4.7 % 0.5 % 0.0 % 5.2 % North America ex-U.S. 4.4 % 0.0 % (1.1 ) % 3.3 % Supranational 1.5 % 0.0 % 0.0 % 1.5 % Total 73.2 % 55.7 % (24.2 ) % 104.7 % Equity Europe ex-U.K. 6.3 % 8.1 % (1.3 ) % 13.1 % U.S. Large Cap 11.6 % 0.1 % (2.3 ) % 9.4 % U.S. Small/Mid Cap 7.4 % 0.0 % (2.0 ) % 5.4 % Emerging Markets 1.9 % 7.1 % (5.3 ) % 3.7 % North America ex-U.S. 0.8 % 2.7 % 0.0 % 3.5 % United Kingdom 2.9 % 0.0 % (0.2 ) % 2.7 % Japan 2.4 % 0.0 % (1.8 ) % 0.6 % Asia/Pacific ex-Japan 0.6 % 1.6 % (2.5 ) % (0.3 ) % Total 33.9 % 19.6 % (15.4 ) % 38.1 % Real Estate-related U.S. 0.7 % 0.0 % 0.0 % 0.7 % Non-U.S. 0.3 % 0.0 % 0.0 % 0.3 % Total 1.0 % 0.0 % 0.0 % 1.0 % Fixed Income (Inflation-adjusted) U.S. 0.7 % 0.0 % 0.0 % 0.7 % Cash Cash & Cash Equivalents (d) 1.9 % Other (e) (46.4 ) % Total Net Exposure Summary 100.0 % (a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio. | |
| Exposure Basis Explanation [Text Block] | (a) Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time. (b) Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions. (c) For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts. (d) Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. (e) Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. Portfolio Composition presents the value of securities, including equivalent exposure of derivative positions. Equivalent exposure is a reasonable approximation of the amount of the underlying asset the portfolio would have to hold to have the same price sensitivity of the derivative contract. Bonds include any accrued interest amounts. Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio. | |
| [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.[15]Includes the effect of any management fee waivers, if applicable.[16]Includes the effect of any management fee waivers, if applicable.[17]Includes the effect of any management fee waivers, if applicable.[18]Includes the effect of any management fee waivers, if applicable.[19]Includes the effect of any management fee waivers, if applicable.[20]Includes the effect of any management fee waivers, if applicable.[21]Expenses are direct expenses and do not include underlying fund fees and expenses.[22]Includes the effect of any management fee waivers, if applicable.[23]Expenses are direct expenses and do not include underlying fund fees and expenses.[24]Includes the effect of any management fee waivers, if applicable.[25]Includes the effect of any management fee waivers, if applicable.[26]Includes the effect of any management fee waivers, if applicable.[27]Includes the effect of any management fee waivers, if applicable.[28]Includes the effect of any management fee waivers, if applicable.[29]Includes the effect of any management fee waivers, if applicable.[30]Includes the effect of any management fee waivers, if applicable.[31]Includes the effect of any management fee waivers, if applicable.[32]Includes the effect of any management fee waivers, if applicable.[33]Includes the effect of any management fee waivers, if applicable.[34]Includes the effect of any management fee waivers, if applicable.[35]Includes the effect of any management fee waivers, if applicable.[36]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 | ||
| C000007237 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 12,847 | $ 12,847 | $ 12,847 | $ 12,472 | $ 11,431 | $ 13,666 | $ 13,860 | $ 12,535 | $ 10,934 | $ 11,272 | $ 10,595 | $ 9,969 | $ 10,000 | |
| Average Annual Return, Percent | 3% | 0.49% | 2.54% | |||||||||||
| C000007238 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 12,519 | $ 12,519 | $ 12,519 | 12,190 | 11,195 | 13,426 | 13,653 | 12,373 | 10,811 | 11,181 | 10,537 | 9,942 | 10,000 | |
| Average Annual Return, Percent | 2.70% | 0.23% | 2.27% | |||||||||||
| C000007239 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 10,675 | $ 10,675 | $ 10,675 | 10,593 | 10,171 | 11,592 | 11,815 | 11,106 | 10,426 | 10,377 | 10,152 | 10,047 | 10,000 | |
| Average Annual Return, Percent | 0.77% | (0.79%) | 0.66% | |||||||||||
| C000007240 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 10,413 | $ 10,413 | $ 10,413 | 10,358 | 9,974 | 11,392 | 11,641 | 10,970 | 10,315 | 10,298 | 10,093 | 10,026 | 10,000 | |
| Average Annual Return, Percent | 0.53% | (1.04%) | 0.41% | |||||||||||
| C000007241 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 15,138 | $ 15,138 | $ 15,138 | 14,158 | 12,595 | 14,075 | 13,601 | 12,942 | 11,273 | 11,631 | 10,902 | 9,578 | 10,000 | |
| Average Annual Return, Percent | 6.92% | 3.18% | 4.23% | |||||||||||
| C000007242 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 14,774 | $ 14,774 | $ 14,774 | 13,869 | 12,330 | 13,820 | 13,406 | 12,786 | 11,173 | 11,547 | 10,862 | 9,558 | 10,000 | |
| Average Annual Return, Percent | 6.53% | 2.93% | 3.98% | |||||||||||
| C000007243 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 21,260 | $ 21,260 | $ 21,260 | 19,505 | 17,002 | 19,992 | 18,296 | 15,795 | 12,408 | 13,638 | 10,282 | 10,032 | 10,000 | |
| Average Annual Return, Percent | 9% | 6.12% | 7.83% | |||||||||||
| C000007244 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 20,727 | $ 20,727 | $ 20,727 | 19,058 | 16,660 | 19,642 | 18,021 | 15,603 | 12,275 | 13,534 | 10,226 | 10,010 | 10,000 | |
| Average Annual Return, Percent | 8.76% | 5.84% | 7.56% | |||||||||||
| C000007245 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 20,671 | $ 20,671 | $ 20,671 | 19,274 | 16,382 | 21,430 | 19,384 | 16,084 | 12,771 | 14,109 | 11,097 | 10,665 | 10,000 | |
| Average Annual Return, Percent | 7.25% | 5.15% | 7.53% | |||||||||||
| C000007246 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 20,153 | $ 20,153 | $ 20,153 | 18,841 | 16,053 | 21,053 | 19,091 | 15,882 | 12,640 | 14,001 | 11,040 | 10,632 | 10,000 | |
| Average Annual Return, Percent | 6.97% | 4.88% | 7.26% | |||||||||||
| C000007247 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 34,494 | $ 34,494 | $ 34,494 | 29,668 | 23,924 | 29,631 | 23,522 | 19,197 | 13,717 | 13,607 | 10,595 | 9,988 | 10,000 | |
| Average Annual Return, Percent | 16.27% | 12.43% | 13.18% | |||||||||||
| C000007248 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 33,666 | $ 33,666 | $ 33,666 | 29,027 | 23,465 | 29,130 | 23,182 | 18,971 | 13,591 | 13,513 | 10,549 | 9,967 | 10,000 | |
| Average Annual Return, Percent | 15.98% | 12.16% | 12.91% | |||||||||||
| C000007249 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 31,948 | $ 31,948 | $ 31,948 | 25,456 | 19,806 | 23,580 | 18,205 | 15,784 | 12,219 | 13,244 | 10,967 | 10,113 | 10,000 | |
| Average Annual Return, Percent | 25.50% | 15.15% | 12.32% | |||||||||||
| C000007250 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 31,156 | $ 31,156 | $ 31,156 | 24,890 | 19,414 | 23,169 | 17,935 | 15,587 | 12,095 | 13,145 | 10,912 | 10,087 | 10,000 | |
| Average Annual Return, Percent | 25.18% | 14.86% | 12.04% | |||||||||||
| C000007261 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 16,617 | $ 16,617 | $ 16,617 | 16,119 | 14,263 | 17,305 | 15,510 | 13,732 | 10,725 | 12,489 | 9,735 | 9,804 | 10,000 | |
| Average Annual Return, Percent | 3.09% | 3.89% | 5.21% | |||||||||||
| C000007262 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 16,210 | $ 16,210 | $ 16,210 | 15,770 | 13,977 | 17,004 | 15,282 | 13,559 | 10,620 | 12,395 | 9,691 | 9,780 | 10,000 | |
| Average Annual Return, Percent | 2.78% | 3.64% | 4.95% | |||||||||||
| C000007263 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 24,667 | $ 24,667 | $ 24,667 | 21,409 | 17,949 | 21,802 | 18,397 | 15,793 | 11,968 | 13,126 | 10,458 | 9,919 | 10,000 | |
| Average Annual Return, Percent | 15.21% | 9.33% | 9.45% | |||||||||||
| C000007264 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 24,056 | $ 24,056 | $ 24,056 | 20,927 | 17,590 | 21,421 | 18,123 | 15,591 | 11,846 | 13,026 | 10,407 | 9,891 | 10,000 | |
| Average Annual Return, Percent | 14.95% | 9.06% | 9.17% | |||||||||||
| C000007267 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 13,001 | $ 13,001 | $ 13,001 | 12,592 | 11,703 | 13,562 | 13,499 | 12,345 | 11,062 | 11,286 | 10,623 | 9,815 | 10,000 | |
| Average Annual Return, Percent | 3.25% | 1.04% | 2.66% | |||||||||||
| C000007268 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 12,686 | $ 12,686 | $ 12,686 | 12,327 | 11,482 | 13,327 | 13,314 | 12,202 | 10,964 | 11,200 | 10,577 | 9,794 | 10,000 | |
| Average Annual Return, Percent | 2.91% | 0.78% | 2.41% | |||||||||||
| C000007271 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 52,491 | $ 52,491 | $ 52,491 | 38,370 | 24,878 | 38,690 | 34,033 | 23,177 | 17,022 | 16,733 | 12,038 | 11,075 | 10,000 | |
| Average Annual Return, Percent | 36.80% | 17.76% | 18.03% | |||||||||||
| C000007272 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 51,228 | $ 51,228 | $ 51,228 | 37,544 | 24,409 | 38,051 | 33,546 | 22,913 | 16,863 | 16,610 | 11,980 | 11,053 | 10,000 | |
| Average Annual Return, Percent | 36.45% | 17.46% | 17.75% | |||||||||||
| C000007281 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 32,345 | $ 32,345 | $ 32,345 | 26,930 | 21,869 | 26,435 | 21,095 | 17,771 | 13,342 | 13,874 | 11,114 | 9,979 | 10,000 | |
| Average Annual Return, Percent | 20.11% | 12.73% | 12.46% | |||||||||||
| C000007282 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 31,567 | $ 31,567 | $ 31,567 | 26,334 | 21,446 | 25,990 | 20,783 | 17,555 | 13,212 | 13,772 | 11,062 | 9,960 | 10,000 | |
| Average Annual Return, Percent | 19.87% | 12.45% | 12.18% | |||||||||||
| C000007285 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 13,965 | $ 13,965 | $ 13,965 | 12,512 | 11,283 | 14,054 | 15,071 | 13,631 | 11,310 | 13,142 | 9,527 | 8,711 | 10,000 | |
| Average Annual Return, Percent | 11.61% | 0.49% | 3.40% | |||||||||||
| C000007286 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 13,626 | $ 13,626 | $ 13,626 | 12,241 | 11,057 | 13,812 | 14,856 | 13,464 | 11,203 | 13,047 | 9,478 | 8,692 | 10,000 | |
| Average Annual Return, Percent | 11.31% | 0.24% | 3.14% | |||||||||||
| C000007287 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 8,978 | $ 8,978 | $ 8,978 | 9,405 | 9,192 | 11,105 | 11,996 | 10,847 | 10,225 | 10,339 | 9,664 | 9,634 | 10,000 | |
| Average Annual Return, Percent | (4.54%) | (3.71%) | (1.07%) | |||||||||||
| C000007288 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 8,754 | $ 8,754 | $ 8,754 | 9,191 | 9,010 | 10,905 | 11,818 | 10,710 | 10,124 | 10,259 | 9,614 | 9,614 | 10,000 | |
| Average Annual Return, Percent | (4.76%) | (3.95%) | (1.32%) | |||||||||||
| C000007289 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 27,789 | $ 27,789 | $ 27,789 | 25,020 | 20,680 | 25,565 | 21,570 | 17,862 | 13,133 | 13,800 | 10,444 | 9,846 | 10,000 | |
| Average Annual Return, Percent | 11.07% | 9.24% | 10.76% | |||||||||||
| C000007290 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 27,099 | $ 27,099 | $ 27,099 | 24,463 | 20,268 | 25,120 | 21,250 | 17,636 | 13,000 | 13,694 | 10,392 | 9,818 | 10,000 | |
| Average Annual Return, Percent | 10.78% | 8.97% | 10.48% | |||||||||||
| C000007291 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Initial Class | |||||||||||||
| Account Value | $ 14,693 | $ 14,693 | $ 14,693 | 13,993 | 12,764 | 13,754 | 13,381 | 12,597 | 10,994 | 11,512 | 10,387 | 9,777 | 10,000 | |
| Average Annual Return, Percent | 5% | 3.13% | 3.92% | |||||||||||
| C000007292 [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Service Class | |||||||||||||
| Account Value | $ 14,324 | $ 14,324 | $ 14,324 | 13,683 | 12,513 | 13,520 | 13,179 | 12,435 | 10,879 | 11,428 | 10,334 | 9,751 | 10,000 | |
| Average Annual Return, Percent | 4.68% | 2.87% | 3.66% | |||||||||||
| 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 | $ 11,432 | $ 11,432 | $ 11,432 | 11,291 | 10,699 | 12,299 | 12,492 | 11,620 | 10,688 | 10,687 | 10,321 | 10,055 | 10,000 | |
| Average Annual Return, Percent | [1],[2],[3],[4] | 1.25% | (0.33%) | 1.35% | ||||||||||
| MSCI All Country World ex US Index net div [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | MSCI All Country World (ex-US) Index (net div) | |||||||||||||
| Account Value | $ 15,985 | $ 15,985 | $ 15,985 | 15,147 | 13,101 | 15,597 | 14,465 | 13,073 | 10,759 | 12,538 | 9,858 | 9,434 | 10,000 | |
| Average Annual Return, Percent | [5],[6] | 5.53% | 4.10% | 4.80% | ||||||||||
| MSCI EAFE Europe Australasia Far East Index net div [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | MSCI EAFE (Europe, Australasia, Far East) Index (net div) | |||||||||||||
| Account Value | $ 16,598 | $ 16,598 | $ 16,598 | 15,987 | 13,521 | 15,805 | 14,205 | 13,176 | 10,798 | 12,526 | 10,018 | 9,919 | 10,000 | |
| Average Annual Return, Percent | [7] | 3.82% | 4.73% | 5.20% | ||||||||||
| Russell 3000 Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index | |||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | 26,334 | 20,907 | 25,877 | 20,593 | 17,035 | 13,002 | 13,721 | 11,327 | 10,048 | 10,000 | |
| Average Annual Return, Percent | [8],[9] | 23.81% | 13.86% | 12.55% | ||||||||||
| 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 | [10],[11] | 25.02% | 14.53% | 13.10% | ||||||||||
| 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 | $ 24,183 | $ 24,183 | $ 24,183 | 20,584 | 16,844 | 20,633 | 17,406 | 14,973 | 11,827 | 13,056 | 10,531 | 9,764 | 10,000 | |
| Average Annual Return, Percent | [12],[13] | 17.49% | 10.06% | 9.23% | ||||||||||
| MSCI Emerging Markets Index net div [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | MSCI Emerging Markets Index (net div) | |||||||||||||
| Account Value | $ 14,293 | $ 14,293 | $ 14,293 | 13,295 | 12,105 | 15,149 | 15,544 | 13,139 | 11,095 | 12,987 | 9,460 | 8,508 | 10,000 | |
| Average Annual Return, Percent | [14] | 7.50% | 1.70% | 3.64% | ||||||||||
| Bloomberg Global Aggregate Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Bloomberg Global Aggregate Index | |||||||||||||
| Account Value | $ 10,151 | $ 10,151 | $ 10,151 | 10,326 | 9,767 | 11,662 | 12,238 | 11,208 | 10,490 | 10,618 | 9,887 | 9,685 | 10,000 | |
| Average Annual Return, Percent | [15],[16] | (1.69%) | (1.96%) | 0.15% | ||||||||||
| Bloomberg U S Credit Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Credit Index | |||||||||||||
| Account Value | $ 12,543 | $ 12,543 | $ 12,543 | 12,294 | 11,364 | 13,410 | 13,556 | 12,397 | 10,894 | 11,129 | 10,481 | 9,923 | 10,000 | |
| Average Annual Return, Percent | [2],[4] | 2.03% | 0.23% | 2.29% | ||||||||||
| Bloomberg U S Government Mortgage Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Government/Mortgage Index | |||||||||||||
| Account Value | $ 10,915 | $ 10,915 | $ 10,915 | 10,825 | 10,364 | 11,793 | 12,005 | 11,287 | 10,585 | 10,488 | 10,245 | 10,113 | 10,000 | |
| Average Annual Return, Percent | [3],[17] | 0.83% | (0.67%) | 0.88% | ||||||||||
| Bloomberg U S Corporate High Yield 2 Issuer Capped Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index | |||||||||||||
| Account Value | $ 16,546 | $ 16,546 | $ 16,546 | 15,293 | 13,481 | 15,178 | 14,419 | 13,470 | 11,783 | 12,033 | 11,194 | 9,557 | 10,000 | |
| Average Annual Return, Percent | [1],[18] | 8.19% | 4.20% | 5.16% | ||||||||||
| MSCI All Country World ex US Growth Index net div [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | MSCI All Country World (ex-US) Growth Index (net div) | |||||||||||||
| Account Value | $ 16,840 | $ 16,840 | $ 16,840 | 16,027 | 14,055 | 18,266 | 17,381 | 14,223 | 11,169 | 13,052 | 9,887 | 9,875 | 10,000 | |
| Average Annual Return, Percent | [5],[6] | 5.07% | 3.44% | 5.35% | ||||||||||
| Russell 1000 Growth Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 1000® Growth Index | |||||||||||||
| Account Value | $ 47,152 | $ 47,152 | $ 47,152 | 35,358 | 24,782 | 34,971 | 27,408 | 19,790 | 14,510 | 14,733 | 11,314 | 10,567 | 10,000 | |
| Average Annual Return, Percent | [8],[9] | 33.36% | 18.96% | 16.78% | ||||||||||
| Standard And Poor s North American Technology Sector Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Standard & Poor's North American Technology Sector Index | |||||||||||||
| Account Value | $ 65,639 | $ 65,639 | $ 65,639 | 48,237 | 29,937 | 46,313 | 36,640 | 25,242 | 17,691 | 17,196 | 12,481 | 10,991 | 10,000 | |
| Average Annual Return, Percent | [10],[19] | 36.08% | 21.06% | 20.70% | ||||||||||
| JPMorgan Global Government Bond Index Unhedged [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | JPMorgan Global Government Bond Index (Unhedged) | |||||||||||||
| Account Value | $ 9,469 | $ 9,469 | $ 9,469 | 9,828 | 9,449 | 11,414 | 12,207 | 11,129 | 10,497 | 10,567 | 9,892 | 9,739 | 10,000 | |
| Average Annual Return, Percent | [15],[16] | (3.65%) | (3.18%) | (0.54%) | ||||||||||
| 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 | $ 30,726 | $ 30,726 | $ 30,726 | 24,734 | 18,566 | 26,006 | 22,208 | 16,623 | 12,525 | 13,633 | 10,487 | 10,155 | 10,000 | |
| Average Annual Return, Percent | [12],[20] | 24.23% | 13.07% | 11.88% | ||||||||||
| MFS Global Tactical Allocation Blended Index [Member] | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | MFS Global Tactical Allocation Blended Index | |||||||||||||
| Account Value | $ 15,893 | $ 15,893 | $ 15,893 | $ 14,717 | $ 13,060 | $ 15,184 | $ 14,332 | $ 13,002 | $ 11,331 | $ 11,576 | $ 10,525 | $ 10,010 | $ 10,000 | |
| Average Annual Return, Percent | [21] | 7.99% | 4.10% | 4.74% | ||||||||||
| [1]Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Corporate High-Yield 2% Issuer Capped Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[2]Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Credit Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Credit Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[3]Effective May 1, 2024, the Bloomberg U.S. Aggregate Bond Index replaced the Bloomberg U.S. Government/Mortgage Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the Bloomberg U.S. Government/Mortgage Index as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[4]Source: FactSet Research Systems Inc.[5]Effective May 1, 2024, the MSCI All Country World (ex-US) Index (net div) replaced the MSCI All Country World (ex-US) Growth Index (net div) as a broad measure of market performance in accordance with new regulatory disclosure requirements. The fund continues to use the MSCI All Country World (ex-US) Growth Index (net div) as an additional benchmark that MFS believes more closely reflects the market segments in which the fund invests.[6]Source: FactSet Research Systems Inc.[7]Source: FactSet Research Systems Inc.[8]Effective May 1, 2024, the Russell 3000 ® ® ® | ||||||||||||||
| Shareholder Report, Holdings (Details) | Dec. 31, 2024 | |
| C000007237 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007237 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.70% | |
| C000007237 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 50.30% | |
| C000007237 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.90% | |
| C000007237 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007237 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007237 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007237 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007237 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | |
| C000007237 [Member] | AUSTRALIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007237 [Member] | BERMUDA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007237 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.60% | |
| C000007237 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.40% | |
| C000007237 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007237 [Member] | IRELAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007237 [Member] | ITALY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007237 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007237 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 72.80% | |
| C000007237 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.60% | |
| C000007237 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007237 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007238 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007238 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.70% | |
| C000007238 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 50.30% | |
| C000007238 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.90% | |
| C000007238 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007238 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007238 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007238 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007238 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | |
| C000007238 [Member] | AUSTRALIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007238 [Member] | BERMUDA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007238 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.60% | |
| C000007238 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.40% | |
| C000007238 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007238 [Member] | IRELAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007238 [Member] | ITALY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007238 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007238 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 72.80% | |
| C000007238 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.60% | |
| C000007238 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007238 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007239 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007239 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0% | |
| C000007239 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007239 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007239 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | |
| C000007239 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 89.80% | |
| C000007239 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007239 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 24% | |
| C000007239 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.20% | |
| C000007240 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007240 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0% | |
| C000007240 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007240 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007240 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | |
| C000007240 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 89.80% | |
| C000007240 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007240 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 24% | |
| C000007240 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.20% | |
| C000007241 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007241 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 44.40% | |
| C000007241 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 37.80% | |
| C000007241 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007241 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007241 [Member] | Standard & Poor's, CCC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.80% | |
| C000007241 [Member] | Standard & Poor's, CC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | |
| C000007241 [Member] | Standard & Poor's, C Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | |
| C000007241 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.60% | [1] |
| C000007241 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007241 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.20% | |
| C000007241 [Member] | Non Fixed Income [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.20% | |
| C000007242 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007242 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 44.40% | |
| C000007242 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 37.80% | |
| C000007242 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007242 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007242 [Member] | Standard & Poor's, CCC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.80% | |
| C000007242 [Member] | Standard & Poor's, CC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | |
| C000007242 [Member] | Standard & Poor's, C Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | |
| C000007242 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.60% | [2] |
| C000007242 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007242 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.20% | |
| C000007242 [Member] | Non Fixed Income [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.20% | |
| C000007243 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007243 [Member] | SAP SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007243 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007243 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007243 [Member] | Roche Holding AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007243 [Member] | Nestle S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007243 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007243 [Member] | Linde PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007243 [Member] | EssilorLuxottica [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007243 [Member] | Amadeus IT Group S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007243 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 24.70% | |
| C000007243 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007243 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007243 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.40% | |
| C000007243 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007243 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007243 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.60% | |
| C000007243 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15% | |
| C000007243 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.10% | |
| C000007243 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007243 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007243 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98% | |
| C000007244 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007244 [Member] | SAP SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007244 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007244 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007244 [Member] | Roche Holding AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007244 [Member] | Nestle S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007244 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007244 [Member] | Linde PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007244 [Member] | EssilorLuxottica [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007244 [Member] | Amadeus IT Group S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007244 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 24.70% | |
| C000007244 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007244 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007244 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.40% | |
| C000007244 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007244 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007244 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.60% | |
| C000007244 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15% | |
| C000007244 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.10% | |
| C000007244 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007244 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007244 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98% | |
| C000007245 [Member] | SAP SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007245 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007245 [Member] | AIB Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007245 [Member] | Resona Holdings Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007245 [Member] | Franco Nevada Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007245 [Member] | Deutsche Boerse AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007245 [Member] | Legrand S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007245 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007245 [Member] | NatWest Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007245 [Member] | TotalEnergies SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007245 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14% | |
| C000007245 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5% | |
| C000007245 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.20% | |
| C000007245 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | |
| C000007245 [Member] | IRELAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007245 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | |
| C000007245 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.30% | |
| C000007245 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.10% | |
| C000007245 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | |
| C000007245 [Member] | SPAIN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007245 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007245 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.80% | |
| C000007246 [Member] | SAP SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007246 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007246 [Member] | AIB Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007246 [Member] | Resona Holdings Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007246 [Member] | Franco Nevada Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007246 [Member] | Deutsche Boerse AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007246 [Member] | Legrand S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007246 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007246 [Member] | NatWest Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007246 [Member] | TotalEnergies SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007246 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14% | |
| C000007246 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5% | |
| C000007246 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.20% | |
| C000007246 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | |
| C000007246 [Member] | IRELAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007246 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | |
| C000007246 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.30% | |
| C000007246 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.10% | |
| C000007246 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | |
| C000007246 [Member] | SPAIN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007246 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007246 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.80% | |
| C000007247 [Member] | Aon PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007247 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007247 [Member] | Church And Dwight Co Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007247 [Member] | Agilent Technologies Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007247 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | |
| C000007247 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.80% | |
| C000007247 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007247 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007247 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007247 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007247 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.10% | |
| C000007247 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.70% | |
| C000007247 [Member] | Real Estate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007247 [Member] | Communications Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.50% | |
| C000007247 [Member] | Consumer Discretionary Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.80% | |
| C000007247 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.40% | |
| C000007247 [Member] | Materials Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007247 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.70% | |
| C000007247 [Member] | Information Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 38.10% | |
| C000007247 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007247 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | |
| C000007247 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.10% | |
| C000007248 [Member] | Aon PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007248 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007248 [Member] | Church And Dwight Co Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007248 [Member] | Agilent Technologies Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007248 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | |
| C000007248 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.80% | |
| C000007248 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007248 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007248 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007248 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007248 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.10% | |
| C000007248 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.70% | |
| C000007248 [Member] | Real Estate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007248 [Member] | Communications Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.50% | |
| C000007248 [Member] | Consumer Discretionary Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.80% | |
| C000007248 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.40% | |
| C000007248 [Member] | Materials Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007248 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.70% | |
| C000007248 [Member] | Information Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 38.10% | |
| C000007248 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007248 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | |
| C000007248 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.10% | |
| C000007249 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.60% | |
| C000007249 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007249 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007249 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007249 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007249 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | |
| C000007249 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007249 [Member] | AbbVie Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007249 [Member] | Johnson And Johnson [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007249 [Member] | Alphabet Inc C [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007249 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.90% | |
| C000007249 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.60% | |
| C000007249 [Member] | Real Estate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007249 [Member] | Communications Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007249 [Member] | Consumer Discretionary Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.40% | |
| C000007249 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007249 [Member] | Materials Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007249 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.30% | |
| C000007249 [Member] | Information Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | |
| C000007249 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007249 [Member] | Energy Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007249 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007249 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.40% | |
| C000007250 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.60% | |
| C000007250 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7% | |
| C000007250 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007250 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007250 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007250 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | |
| C000007250 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007250 [Member] | AbbVie Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007250 [Member] | Johnson And Johnson [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007250 [Member] | Alphabet Inc C [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007250 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.90% | |
| C000007250 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.60% | |
| C000007250 [Member] | Real Estate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007250 [Member] | Communications Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007250 [Member] | Consumer Discretionary Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.40% | |
| C000007250 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.50% | |
| C000007250 [Member] | Materials Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007250 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.30% | |
| C000007250 [Member] | Information Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | |
| C000007250 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007250 [Member] | Energy Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007250 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007250 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.40% | |
| C000007255 [Member] | Zero To 7 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 35.30% | |
| C000007255 [Member] | Thirty To 59 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 28.30% | |
| C000007255 [Member] | Sixty To 89 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.40% | |
| C000007255 [Member] | Ninety To 365 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.50% | |
| C000007255 [Member] | Eight To 29 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 17.50% | |
| C000007255 [Member] | Fixed Income Credit Quality A One Plus [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 55.30% | |
| C000007255 [Member] | Fixed Income Credit Quality A One [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 44.70% | |
| C000007255 [Member] | U S Treasury and U S Government Agency Securities and Equivalents [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 71% | |
| C000007255 [Member] | Repurchase Agreements collateralized by U S Treasury and or U S Government Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 29% | |
| C000007256 [Member] | Zero To 7 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 35.30% | |
| C000007256 [Member] | Thirty To 59 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 28.30% | |
| C000007256 [Member] | Sixty To 89 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.40% | |
| C000007256 [Member] | Ninety To 365 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.50% | |
| C000007256 [Member] | Eight To 29 days [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 17.50% | |
| C000007256 [Member] | Fixed Income Credit Quality A One Plus [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 55.30% | |
| C000007256 [Member] | Fixed Income Credit Quality A One [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 44.70% | |
| C000007256 [Member] | U S Treasury and U S Government Agency Securities and Equivalents [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 71% | |
| C000007256 [Member] | Repurchase Agreements collateralized by U S Treasury and or U S Government Agency Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 29% | |
| C000007261 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007261 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007261 [Member] | Roche Holding AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007261 [Member] | Nestle S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007261 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007261 [Member] | Linde PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007261 [Member] | NatWest Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007261 [Member] | Aon PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007261 [Member] | Novo Nordisk A S B [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007261 [Member] | ASML Holding N V [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007261 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 17.50% | |
| C000007261 [Member] | AUSTRALIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007261 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007261 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.70% | |
| C000007261 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.20% | |
| C000007261 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.50% | |
| C000007261 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6% | |
| C000007261 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.80% | |
| C000007261 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | |
| C000007261 [Member] | DENMARK | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007261 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007261 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97% | |
| C000007262 [Member] | Schneider Electric SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007262 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007262 [Member] | Roche Holding AG [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007262 [Member] | Nestle S A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007262 [Member] | LVMH Moet Hennessy Louis Vuitton SE [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007262 [Member] | Linde PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007262 [Member] | NatWest Group PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007262 [Member] | Aon PLC [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007262 [Member] | Novo Nordisk A S B [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007262 [Member] | ASML Holding N V [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007262 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 17.50% | |
| C000007262 [Member] | AUSTRALIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007262 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.90% | |
| C000007262 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.70% | |
| C000007262 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.20% | |
| C000007262 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.50% | |
| C000007262 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6% | |
| C000007262 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.80% | |
| C000007262 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | |
| C000007262 [Member] | DENMARK | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007262 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007262 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97% | |
| C000007263 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007263 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007263 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.50% | |
| C000007263 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.90% | |
| C000007263 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007263 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007263 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007263 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007263 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007263 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007263 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.80% | |
| C000007263 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007263 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007263 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.70% | |
| C000007263 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.30% | |
| C000007263 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 66.70% | |
| C000007263 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5% | |
| C000007263 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.50% | |
| C000007263 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007263 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007263 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007263 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.40% | |
| C000007264 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007264 [Member] | Hitachi Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007264 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.50% | |
| C000007264 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.90% | |
| C000007264 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007264 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007264 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007264 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007264 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007264 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007264 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8.80% | |
| C000007264 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007264 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007264 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.70% | |
| C000007264 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.30% | |
| C000007264 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 66.70% | |
| C000007264 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5% | |
| C000007264 [Member] | NETHERLANDS | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.50% | |
| C000007264 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007264 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007264 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.60% | |
| C000007264 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.40% | |
| C000007267 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.50% | |
| C000007267 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.30% | |
| C000007267 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.50% | |
| C000007267 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007267 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.60% | |
| C000007267 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007267 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.70% | |
| C000007267 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007267 [Member] | Standard & Poor's, CCC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007267 [Member] | Standard & Poor's, C Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0% | |
| C000007267 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.80% | |
| C000007267 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007267 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 26.50% | |
| C000007267 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007268 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.50% | |
| C000007268 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.30% | |
| C000007268 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.50% | |
| C000007268 [Member] | Fitch, B Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007268 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.60% | |
| C000007268 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007268 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.70% | |
| C000007268 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007268 [Member] | Standard & Poor's, CCC Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007268 [Member] | Standard & Poor's, C Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0% | |
| C000007268 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.80% | |
| C000007268 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.20% | |
| C000007268 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 26.50% | |
| C000007268 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007271 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007271 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.40% | |
| C000007271 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.20% | |
| C000007271 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007271 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8% | |
| C000007271 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007271 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.10% | |
| C000007271 [Member] | Broadcom Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007271 [Member] | Oracle Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007271 [Member] | ServiceNow Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007271 [Member] | Electronics [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.60% | |
| C000007271 [Member] | Internet [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 20.90% | |
| C000007271 [Member] | Computer Software Systems [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.80% | |
| C000007271 [Member] | Computer Software [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 29.40% | |
| C000007271 [Member] | Business Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000007271 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007271 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.50% | |
| C000007272 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007272 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.40% | |
| C000007272 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.20% | |
| C000007272 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007272 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 8% | |
| C000007272 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007272 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.10% | |
| C000007272 [Member] | Broadcom Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | |
| C000007272 [Member] | Oracle Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3% | |
| C000007272 [Member] | ServiceNow Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007272 [Member] | Electronics [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.60% | |
| C000007272 [Member] | Internet [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 20.90% | |
| C000007272 [Member] | Computer Software Systems [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.80% | |
| C000007272 [Member] | Computer Software [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 29.40% | |
| C000007272 [Member] | Business Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.40% | |
| C000007272 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007272 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 97.50% | |
| C000007281 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.80% | |
| C000007281 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007281 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.60% | |
| C000007281 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.80% | |
| C000007281 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007281 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007281 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007281 [Member] | Johnson And Johnson [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.40% | |
| C000007281 [Member] | JPMorgan Chase And Co [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007281 [Member] | Marvell Technology Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007281 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.30% | |
| C000007281 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11% | |
| C000007281 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007281 [Member] | Energy Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.10% | |
| C000007281 [Member] | Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 37.60% | |
| C000007281 [Member] | Consumer Cyclicals [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13% | |
| C000007281 [Member] | Telecommunications and Cable Television [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007281 [Member] | Capital Goods [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.40% | |
| C000007281 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000007281 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.60% | |
| C000007281 [Member] | Securities Sold Short [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (0.10%) | |
| C000007282 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.80% | |
| C000007282 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007282 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.60% | |
| C000007282 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.80% | |
| C000007282 [Member] | Alphabet Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | |
| C000007282 [Member] | Amazon com Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007282 [Member] | Meta Platforms Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007282 [Member] | Johnson And Johnson [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.40% | |
| C000007282 [Member] | JPMorgan Chase And Co [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007282 [Member] | Marvell Technology Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007282 [Member] | Financial Services Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.30% | |
| C000007282 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11% | |
| C000007282 [Member] | Consumer Staples Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.40% | |
| C000007282 [Member] | Energy Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.10% | |
| C000007282 [Member] | Technology Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 37.60% | |
| C000007282 [Member] | Consumer Cyclicals [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13% | |
| C000007282 [Member] | Telecommunications and Cable Television [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007282 [Member] | Capital Goods [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.40% | |
| C000007282 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.50% | |
| C000007282 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 99.60% | |
| C000007282 [Member] | Securities Sold Short [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | (0.10%) | |
| C000007285 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.90% | |
| C000007285 [Member] | Tencent Holdings Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.20% | |
| C000007285 [Member] | Samsung Electronics Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007285 [Member] | Alibaba Group Holding Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.20% | |
| C000007285 [Member] | Infosys Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007285 [Member] | China Construction Bank Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007285 [Member] | Tata Consultancy Services Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007285 [Member] | HDFC Bank Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007285 [Member] | Delta Electronics Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007285 [Member] | Ping An Insurance Co of China Ltd H [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.80% | |
| C000007285 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.40% | |
| C000007285 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007285 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.30% | |
| C000007285 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.20% | |
| C000007285 [Member] | THAILAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007285 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.20% | |
| C000007285 [Member] | MEXICO | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007285 [Member] | BRAZIL | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007285 [Member] | INDONESIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007285 [Member] | INDIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.80% | |
| C000007285 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007285 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98% | |
| C000007286 [Member] | Taiwan Semiconductor Manufacturing Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.90% | |
| C000007286 [Member] | Tencent Holdings Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.20% | |
| C000007286 [Member] | Samsung Electronics Co Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007286 [Member] | Alibaba Group Holding Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.20% | |
| C000007286 [Member] | Infosys Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.60% | |
| C000007286 [Member] | China Construction Bank Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007286 [Member] | Tata Consultancy Services Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007286 [Member] | HDFC Bank Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007286 [Member] | Delta Electronics Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.90% | |
| C000007286 [Member] | Ping An Insurance Co of China Ltd H [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.80% | |
| C000007286 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.40% | |
| C000007286 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007286 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.30% | |
| C000007286 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 27.20% | |
| C000007286 [Member] | THAILAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007286 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.20% | |
| C000007286 [Member] | MEXICO | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007286 [Member] | BRAZIL | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | |
| C000007286 [Member] | INDONESIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.50% | |
| C000007286 [Member] | INDIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.80% | |
| C000007286 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2% | |
| C000007286 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98% | |
| C000007287 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10% | |
| C000007287 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.70% | |
| C000007287 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.40% | |
| C000007287 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007287 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.40% | |
| C000007287 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007287 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007287 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007287 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007287 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007287 [Member] | ITALY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.60% | |
| C000007287 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11% | |
| C000007287 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 49% | |
| C000007287 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007287 [Member] | SPAIN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007287 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007287 [Member] | GREECE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.70% | |
| C000007287 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 95.50% | |
| C000007287 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007287 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 41.90% | |
| C000007287 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007288 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10% | |
| C000007288 [Member] | Fitch, A Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.70% | |
| C000007288 [Member] | Fitch, BBB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 15.40% | |
| C000007288 [Member] | Fitch, BB Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.70% | |
| C000007288 [Member] | Fitch, AA Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.40% | |
| C000007288 [Member] | Money Market Funds Quality [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007288 [Member] | Moody's, Aaa Rating [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.20% | |
| C000007288 [Member] | Not Rated [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | |
| C000007288 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.50% | |
| C000007288 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007288 [Member] | ITALY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.60% | |
| C000007288 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11% | |
| C000007288 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 49% | |
| C000007288 [Member] | GERMANY | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007288 [Member] | SPAIN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.60% | |
| C000007288 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007288 [Member] | GREECE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.70% | |
| C000007288 [Member] | Fixed Income Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 95.50% | |
| C000007288 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.50% | |
| C000007288 [Member] | US Government Debt Securities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 41.90% | |
| C000007288 [Member] | Federal Agencies [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.60% | |
| C000007289 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007289 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007289 [Member] | Agilent Technologies Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.10% | |
| C000007289 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.40% | |
| C000007289 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007289 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007289 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007289 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007289 [Member] | Tencent Holdings Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007289 [Member] | HDFC Bank Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007289 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007289 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | |
| C000007289 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007289 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007289 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 71.60% | |
| C000007289 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007289 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007289 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007289 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007289 [Member] | INDIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007289 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007289 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.90% | |
| C000007290 [Member] | Taiwan Semiconductor Manufacturing Co Ltd ADR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007290 [Member] | Salesforce Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007290 [Member] | Agilent Technologies Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.10% | |
| C000007290 [Member] | Microsoft Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.40% | |
| C000007290 [Member] | Apple Inc [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007290 [Member] | NVIDIA Corp [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.10% | |
| C000007290 [Member] | Visa Inc A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007290 [Member] | Accenture PLC A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.90% | |
| C000007290 [Member] | Tencent Holdings Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007290 [Member] | HDFC Bank Ltd [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | |
| C000007290 [Member] | Other Countries [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | |
| C000007290 [Member] | CANADA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | |
| C000007290 [Member] | SWITZERLAND | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.70% | |
| C000007290 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.40% | |
| C000007290 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 71.60% | |
| C000007290 [Member] | FRANCE | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.40% | |
| C000007290 [Member] | TAIWAN | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.30% | |
| C000007290 [Member] | CHINA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.80% | |
| C000007290 [Member] | KOREA, REPUBLIC OF | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.30% | |
| C000007290 [Member] | INDIA | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | |
| C000007290 [Member] | Money Market Funds [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 1.10% | |
| C000007290 [Member] | Equity [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 98.90% | |
| C000007291 [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Long Exposure | 100% | [3],[4] |
| C000007291 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.50% | [4],[5] |
| Percent of Total Long Exposure | 3.60% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 7.10% | [3],[4] |
| C000007291 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.70% | [4],[5] |
| Percent of Total Long Exposure | 0.50% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 5.20% | [3],[4] |
| C000007291 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 33% | [4],[5] |
| Percent of Total Long Exposure | 46.90% | [4] |
| Percent of Total Short Exposure | (18.50%) | [4] |
| Percent of Net Long Exposure | 61.40% | [3],[4] |
| C000007291 [Member] | Defined Benefit Plan, Equity Securities, US, Large Cap [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.60% | [4],[5] |
| Percent of Total Long Exposure | 0.10% | [4] |
| Percent of Total Short Exposure | (2.30%) | [4] |
| Percent of Net Long Exposure | 9.40% | [3],[4] |
| C000007291 [Member] | Cash and Cash Equivalents [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Long Exposure | 1.90% | [3],[4],[6] |
| C000007291 [Member] | Other Investments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Short Exposure | (46.40%) | [3],[4],[7] |
| C000007291 [Member] | Equity Emerging Markets [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | [4],[5] |
| Percent of Total Long Exposure | 7.10% | [4] |
| Percent of Total Short Exposure | (5.30%) | [4] |
| Percent of Net Long Exposure | 3.70% | [3],[4] |
| C000007291 [Member] | U S Small Mid Cap [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.40% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | (2.00%) | [4] |
| Percent of Net Long Exposure | 5.40% | [3],[4] |
| C000007291 [Member] | Asia Pacific ex Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.50% | [4],[5] |
| Percent of Total Long Exposure | 4.70% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 6.20% | [3],[4] |
| C000007291 [Member] | Europe ex U K [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 10.30% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | (4.60%) | [4] |
| Percent of Net Long Exposure | 5.70% | [3],[4] |
| C000007291 [Member] | North America ex U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.40% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | (1.10%) | [4] |
| Percent of Net Long Exposure | 3.30% | [3],[4] |
| C000007291 [Member] | Supranational [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.50% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 1.50% | [3],[4] |
| C000007291 [Member] | Equity Europe ex U K [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.30% | [4],[5] |
| Percent of Total Long Exposure | 8.10% | [4] |
| Percent of Total Short Exposure | (1.30%) | [4] |
| Percent of Net Long Exposure | 13.10% | [3],[4] |
| C000007291 [Member] | Equity North America ex U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.80% | [4],[5] |
| Percent of Total Long Exposure | 2.70% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 3.50% | [3],[4] |
| C000007291 [Member] | Emerging Markets [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 14.30% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 14.30% | [3],[4] |
| C000007291 [Member] | Fixed Income Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 73.20% | [4],[5] |
| Percent of Total Long Exposure | 55.70% | [4] |
| Percent of Total Short Exposure | (24.20%) | [4] |
| Percent of Net Long Exposure | 104.70% | [3],[4] |
| C000007291 [Member] | Equity Asia Pacific ex Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.60% | [4],[5] |
| Percent of Total Long Exposure | 1.60% | [4] |
| Percent of Total Short Exposure | (2.50%) | [4] |
| Percent of Net Short Exposure | (0.30%) | [3],[4] |
| C000007291 [Member] | Equity United Kingdom [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.90% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | (0.20%) | [4] |
| Percent of Net Long Exposure | 2.70% | [3],[4] |
| C000007291 [Member] | Equity Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.40% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | (1.80%) | [4] |
| Percent of Net Long Exposure | 0.60% | [3],[4] |
| C000007291 [Member] | Equity Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 33.90% | [4],[5] |
| Percent of Total Long Exposure | 19.60% | [4] |
| Percent of Total Short Exposure | (15.40%) | [4] |
| Percent of Net Long Exposure | 38.10% | [3],[4] |
| C000007291 [Member] | Real Estate related U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 0.70% | [3],[4] |
| C000007291 [Member] | Real Estate related Non U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.30% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 0.30% | [3],[4] |
| C000007291 [Member] | Real Estate related Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 1% | [3],[4] |
| C000007291 [Member] | Fixed Income Inflation adjusted U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | [4],[5] |
| Percent of Total Long Exposure | 0% | [4] |
| Percent of Total Short Exposure | 0% | [4] |
| Percent of Net Long Exposure | 0.70% | [3],[4] |
| C000007292 [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Long Exposure | 100% | [8],[9] |
| C000007292 [Member] | UNITED KINGDOM | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.50% | [9],[10] |
| Percent of Total Long Exposure | 3.60% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 7.10% | [8],[9] |
| C000007292 [Member] | JAPAN | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.70% | [9],[10] |
| Percent of Total Long Exposure | 0.50% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 5.20% | [8],[9] |
| C000007292 [Member] | UNITED STATES | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 33% | [9],[10] |
| Percent of Total Long Exposure | 46.90% | [9] |
| Percent of Total Short Exposure | (18.50%) | [9] |
| Percent of Net Long Exposure | 61.40% | [8],[9] |
| C000007292 [Member] | Defined Benefit Plan, Equity Securities, US, Large Cap [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.60% | [9],[10] |
| Percent of Total Long Exposure | 0.10% | [9] |
| Percent of Total Short Exposure | (2.30%) | [9] |
| Percent of Net Long Exposure | 9.40% | [8],[9] |
| C000007292 [Member] | Cash and Cash Equivalents [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Long Exposure | 1.90% | [8],[9],[11] |
| C000007292 [Member] | Other Investments [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Short Exposure | (46.40%) | [8],[9],[12] |
| C000007292 [Member] | Equity Emerging Markets [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | [9],[10] |
| Percent of Total Long Exposure | 7.10% | [9] |
| Percent of Total Short Exposure | (5.30%) | [9] |
| Percent of Net Long Exposure | 3.70% | [8],[9] |
| C000007292 [Member] | U S Small Mid Cap [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.40% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | (2.00%) | [9] |
| Percent of Net Long Exposure | 5.40% | [8],[9] |
| C000007292 [Member] | Asia Pacific ex Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.50% | [9],[10] |
| Percent of Total Long Exposure | 4.70% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 6.20% | [8],[9] |
| C000007292 [Member] | Europe ex U K [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 10.30% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | (4.60%) | [9] |
| Percent of Net Long Exposure | 5.70% | [8],[9] |
| C000007292 [Member] | North America ex U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.40% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | (1.10%) | [9] |
| Percent of Net Long Exposure | 3.30% | [8],[9] |
| C000007292 [Member] | Supranational [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.50% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 1.50% | [8],[9] |
| C000007292 [Member] | Equity Europe ex U K [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.30% | [9],[10] |
| Percent of Total Long Exposure | 8.10% | [9] |
| Percent of Total Short Exposure | (1.30%) | [9] |
| Percent of Net Long Exposure | 13.10% | [8],[9] |
| C000007292 [Member] | Equity North America ex U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.80% | [9],[10] |
| Percent of Total Long Exposure | 2.70% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 3.50% | [8],[9] |
| C000007292 [Member] | Emerging Markets [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 14.30% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 14.30% | [8],[9] |
| C000007292 [Member] | Fixed Income Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 73.20% | [9],[10] |
| Percent of Total Long Exposure | 55.70% | [9] |
| Percent of Total Short Exposure | (24.20%) | [9] |
| Percent of Net Long Exposure | 104.70% | [8],[9] |
| C000007292 [Member] | Equity Asia Pacific ex Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.60% | [9],[10] |
| Percent of Total Long Exposure | 1.60% | [9] |
| Percent of Total Short Exposure | (2.50%) | [9] |
| Percent of Net Short Exposure | (0.30%) | [8],[9] |
| C000007292 [Member] | Equity United Kingdom [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.90% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | (0.20%) | [9] |
| Percent of Net Long Exposure | 2.70% | [8],[9] |
| C000007292 [Member] | Equity Japan [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.40% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | (1.80%) | [9] |
| Percent of Net Long Exposure | 0.60% | [8],[9] |
| C000007292 [Member] | Equity Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 33.90% | [9],[10] |
| Percent of Total Long Exposure | 19.60% | [9] |
| Percent of Total Short Exposure | (15.40%) | [9] |
| Percent of Net Long Exposure | 38.10% | [8],[9] |
| C000007292 [Member] | Real Estate related U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 0.70% | [8],[9] |
| C000007292 [Member] | Real Estate related Non U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.30% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 0.30% | [8],[9] |
| C000007292 [Member] | Real Estate related Total [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 1% | [8],[9] |
| C000007292 [Member] | Fixed Income Inflation adjusted U S [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | [9],[10] |
| Percent of Total Long Exposure | 0% | [9] |
| Percent of Total Short Exposure | 0% | [9] |
| Percent of Net Long Exposure | 0.70% | [8],[9] |
| [1]The fund invests a portion of its assets in Exchange-Traded Funds (ETFs) or Options on ETFs to gain fixed income exposure. Percentages include the direct exposure from investing in ETFs or Options on ETFs and not the indirect exposure to the underlying holdings.[2]The fund invests a portion of its assets in Exchange-Traded Funds (ETFs) or Options on ETFs to gain fixed income exposure. Percentages include the direct exposure from investing in ETFs or Options on ETFs and not the indirect exposure to the underlying holdings.[3]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[4]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[5]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[6]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[7]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions.[8]For purposes of this presentation, the components include the value of securities, less any securities sold short, and reflect the impact of the equivalent exposure of all derivative positions. These amounts may be negative from time to time. The bond component will include any accrued interest amounts.[9]Represents the tactical overlay portion of the portfolio which is how the fund manages its exposure to markets and currencies through the use of derivative positions. Percentages reflect the equivalent exposure of those derivative positions.[10]Represents the actively managed portion of the portfolio and for purposes of this presentation, components include the value of securities, less any securities sold short. The bond component will include any accrued interest amounts. This also reflects the equivalent exposure of certain derivative positions. These amounts may be negative from time to time.[11]Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities.[12]Other includes currency derivatives and/or the offsetting of the leverage produced by derivative positions. | ||
