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Label Element Value
MFS Inflation-Adjusted Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MFS Inflation-Adjusted Bond Fund Summary of Key Information
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return that exceeds the rate of inflation over the long-term, with an emphasis on current income, but also considering capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

 

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 11 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Feb. 29, 2024
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 86% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 86.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

 

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in inflation-adjusted debt instruments and other instruments with similar economic characteristics.

 

MFS generally focuses the fund’s investments in inflation-adjusted debt instruments issued by the U.S. Treasury. MFS may also invest the fund’s assets in other inflation-adjusted debt instruments and non-inflation-adjusted debt instruments, including corporate bonds, foreign government securities, securitized instruments, and other debt instruments.

 

MFS generally invests substantially all of the fund’s assets in investment grade quality debt instruments.

 

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

 

MFS may invest the fund’s assets in foreign securities.

 

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, and swaps.

 

MFS allocates the fund’s assets across maturities and types of debt instruments based on its evaluation of macroeconomic factors, including interest rates, inflation rates, and monetary and fiscal policies.

 

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative screening tools that systematically evaluate instruments may also be considered. In structuring the fund, MFS also considers top-down factors.

 

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

 

The principal risks of investing in the fund are:

 

Investment Selection Risk: MFS' investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

 

Debt Market Risk: Debt markets can be volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single instrument, issuer, or borrower, a particular type of instrument, issuer, or borrower, a segment of the debt markets or the debt markets generally. Certain events can have a dramatic adverse effect on debt markets and may lead to periods of high volatility and reduced liquidity in a debt market or segment of a debt market.

 

Interest Rate Risk: In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities or durations, or that do not pay current interest.

 

Credit Risk: The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or other entity responsible for payment, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in, or perceptions of, the financial condition of the issuer, borrower, counterparty, or other entity, or underlying collateral or assets, or changes in, or perceptions of, specific or general market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.

 

U.S. Government securities not supported as to the payment of principal or interest by the U.S. Treasury are subject to greater credit risk than are U.S. Government securities supported by the U.S. Treasury.

 

Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

 

Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging markets or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

 

Focus Risk: Issuers in a single country or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the countries and regions to which the fund is exposed. If MFS invests a significant percentage of the fund's assets in a single issuer or small number of issuers, the fund’s performance could be more volatile than the performance of more diversified funds.

 

Prepayment/Extension Risk: Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

 

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost. Derivatives can involve leverage.

 

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

 

Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability or willingness to perform in accordance with the terms of the transaction.

 

Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

 

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares. These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would.
Risk Lose Money [Text] rr_RiskLoseMoney As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
RIsk Not Insured [Text] rr_RiskNotInsured An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

 

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-225-2606
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress mfs.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Class A Bar Chart.
Bar Chart Narrative [Text Block] rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the period(s) shown in the bar chart, the highest quarterly return was 4.52% (for the calendar quarter ended March 31, 2016) and the lowest quarterly return was (7.09)% (for the calendar quarter ended June 30, 2013).
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.52%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.09%)
Performance Table Heading rr_PerformanceTableHeading Performance Table.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (Reflects no deduction for fees, expenses, or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax

 

returns for the fund’s other classes of shares will vary from the returns shown.
Average Annual Return, Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (For the Periods Ended December 31, 2022)
MFS Inflation-Adjusted Bond Fund | Bloomberg U.S. Treasury Inflation Protected Securities Index  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.85%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.11%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.12%
MFS Inflation-Adjusted Bond Fund | A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.25%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.82%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.65%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 489
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 659
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,380
Annual Return 2013 rr_AnnualReturn2013 (9.38%)
Annual Return 2014 rr_AnnualReturn2014 2.74%
Annual Return 2015 rr_AnnualReturn2015 (2.35%)
Annual Return 2016 rr_AnnualReturn2016 3.98%
Annual Return 2017 rr_AnnualReturn2017 2.41%
Annual Return 2018 rr_AnnualReturn2018 (1.97%)
Annual Return 2019 rr_AnnualReturn2019 7.99%
Annual Return 2020 rr_AnnualReturn2020 10.25%
Annual Return 2021 rr_AnnualReturn2021 4.50%
Annual Return 2022 rr_AnnualReturn2022 (11.91%)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (15.65%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.57%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (0.04%)
MFS Inflation-Adjusted Bond Fund | A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (18.11%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 (0.92%)
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (1.09%)
MFS Inflation-Adjusted Bond Fund | A | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (9.22%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 (0.15%)
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (0.46%)
MFS Inflation-Adjusted Bond Fund | B  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 4.00%
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.57%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.40%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 543 [3]
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 779 [3]
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,039 [3]
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,651 [3]
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 143 [3]
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 479 [3]
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 839 [3]
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,651 [3]
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (15.91%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.33%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (0.20%)
MFS Inflation-Adjusted Bond Fund | C  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.57%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 253 [3]
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 489 [3]
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 849 [3]
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,660 [3]
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 153 [3]
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 489 [3]
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 849 [3]
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,660 [3]
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (13.62%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.55%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (0.28%)
MFS Inflation-Adjusted Bond Fund | I  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.57%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 176
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 311
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 707
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.85%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.58%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.52%
MFS Inflation-Adjusted Bond Fund | R1  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.57%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 153
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 489
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 849
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,861
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (12.67%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.56%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 (0.46%)
MFS Inflation-Adjusted Bond Fund | R2  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.07%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 333
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 583
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,299
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (12.33%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.07%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.03%
MFS Inflation-Adjusted Bond Fund | R3  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.82%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 255
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 448
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,007
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (12.10%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.33%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.28%
MFS Inflation-Adjusted Bond Fund | R4  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.57%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 176
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 311
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 707
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.78%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.56%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.53%
MFS Inflation-Adjusted Bond Fund | R6  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.44%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.49%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 150
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 267
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 609
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.84%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.66%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.62%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
[2] Massachusetts Financial Services Company (MFS) has agreed in writing to reduce its management fee to 0.40% of the fund's average daily net assets annually up to $1 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least February 29, 2024. MFS has agreed in writing to waive at least 0.01% of the fund's management fee as part of an agreement pursuant to which MFS has agreed to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least February 29, 2024. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class A and Class B service fee to 0.15% of each class' average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least February 29, 2024.
[3] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.