Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Aug. 28, 2011
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	Summary of Key Information
Investment Objective, Heading	rr_ObjectiveHeading	Investment Objective
investment Objective, Primary	rr_ObjectivePrimaryTextBlock	The fund's investment objective is to seek total return with an emphasis on current income, but also considering capital appreciation.
Expense, Heading	rr_ExpenseHeading	Fees and Expenses
Expense, Narrative	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in "Sales Charges and Waivers or Reductions" on page 9 of the fund's prospectus and "Waivers of Sales Charges" on page 14 of the fund's statement of additional information Part I.
Shareholder Fees, Caption	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment):
Operating Expenses, Caption	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover, Heading	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover	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 67% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	67.00%
Expense Breakpoint, Discounts	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required Amount	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 50,000
Expense Example, Heading	rr_ExpenseExampleHeading	Example
Expense Example, Narrative	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	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Investment Strategy, Heading	rr_StrategyHeading	Principal Investment Strategies
Investment Strategy, Narrative	rr_StrategyNarrativeTextBlock	MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in debt instruments. Debt instruments include corporate bonds, U.S. Government securities, collateralized instruments, municipal instruments, foreign government securities, inflation-adjusted bonds, and other obligations to repay money borrowed. MFS primarily invests the fund's assets in investment grade debt instruments, but may also invest in lower quality debt instruments. MFS may invest the fund's assets in foreign securities, including emerging market 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, structured securities, inverse floating rate instruments, and swaps. A team of investment research analysts selects investments for the fund. MFS allocates the fund's assets to analysts by sectors of the debt market. MFS uses a 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 in light of issuers' current financial condition and current market, economic, political, and regulatory conditions. Factors considered may include the instrument's credit quality, collateral characteristics, and indenture provisions, and the issuer's management ability, capital structure, leverage, and ability to meet its current obligations. Quantitative models that systematically evaluate the structure of the debt instrument and its features may also be considered.
Risk, Heading	rr_RiskHeading	Principal Risks
Risk, Narrative	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: Interest Rate Risk: The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes. Credit Risk: The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral and can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, or other conditions. Lower quality debt instruments (commonly referred to as "high yield securities" or "junk bonds") can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments. Foreign and Emerging Markets Risk: Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, political, regulatory, geopolitical, or other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets and less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets. Currency Risk: The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, political, regulatory, geopolitical or other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency. 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. Inflation-Adjusting 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. Municipal Risk: The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market. 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. Liquidity Risk: It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price. 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 to perform in accordance with the terms of the transaction. Investment Selection Risk: The MFS analysis of an investment can be incorrect and 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.
Risk, Lose Money	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 Depository Institution	rr_RiskNotInsuredDepositoryInstitution	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	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	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 Number	rr_PerformanceAvailabilityPhone	1-800-225-2606
Performance, Availability Website Address	rr_PerformanceAvailabilityWebSiteAddress	mfs.com
Performance, Past Does Not Indicate Future	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	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	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	rr_BarChartClosingTextBlock	The total return for the six-month period ended June 30, 2011 was 3.03%. During the period(s) shown in the bar chart, the highest quarterly return was 8.29% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (3.24)% (for the calendar quarter ended September 30, 2008).
Performance Table, Heading	rr_PerformanceTableHeading	Performance Table.
Index No Deduction for Fees, Expenses, Taxes	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-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table, One Class of after Tax Shown	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	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-deferred 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 Returns, Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns (for the Periods Ended December 31, 2010)
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund | A
Risk/Return:	rr_RiskReturnAbstract
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-08-31
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2011
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.03%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.29%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.24%)
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund | B
Risk/Return:	rr_RiskReturnAbstract
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-08-31
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund | 529A
Risk/Return:	rr_RiskReturnAbstract
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-08-31
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund | 529B
Risk/Return:	rr_RiskReturnAbstract
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-08-31
MFS Research Bond Fund (Prospectus Summary) | MFS Research Bond Fund | 529C
Risk/Return:	rr_RiskReturnAbstract
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-08-31
MFS Research Bond Fund | Barclays Capital U.S. Aggregate Bond Index
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Capital U.S. Aggregate Bond Index
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	6.54%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.80%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.84%
MFS Research Bond Fund | A
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	A
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.75%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	rr_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.91%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.10%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.81%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	554
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	743
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	948
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,537
Annual Return 2001	rr_AnnualReturn2001	8.95%
Annual Return 2002	rr_AnnualReturn2002	10.43%
Annual Return 2003	rr_AnnualReturn2003	6.87%
Annual Return 2004	rr_AnnualReturn2004	4.72%
Annual Return 2005	rr_AnnualReturn2005	2.01%
Annual Return 2006	rr_AnnualReturn2006	4.14%
Annual Return 2007	rr_AnnualReturn2007	3.94%
Annual Return 2008	rr_AnnualReturn2008	(6.08%)
Annual Return 2009	rr_AnnualReturn2009	20.71%
Annual Return 2010	rr_AnnualReturn2010	8.29%
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	3.15%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.83%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.69%
MFS Research Bond Fund | A | After Taxes on Distributions
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	1.69%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	2.99%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.69%
MFS Research Bond Fund | A | After Taxes on Distributions and Sales
Risk/Return:	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	2.02%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	3.01%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.65%
MFS Research Bond Fund | B
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	B AND 529B
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%
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.66%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.61%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	564
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	820
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,099
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,765
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	164
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	520
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	899
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,765
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	3.43%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.64%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.50%
MFS Research Bond Fund | C
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	C AND 529C
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%
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.66%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.66%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	269
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	525
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	904
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,969
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	169
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	525
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	904
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,969
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	6.38%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.94%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.32%
MFS Research Bond Fund | I
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	I AND W
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.66%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.66%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	68
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	212
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	370
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	827
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	8.45%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	6.01%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	6.40%
MFS Research Bond Fund | W
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	I AND W
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	W
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.10%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.76%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.76%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	78
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	244
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	424
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	947
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	W Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	8.34%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.91%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	6.25%
MFS Research Bond Fund | 529A
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	529A
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.75%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.15%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.86%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	559
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	768
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	994
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,644
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	3.16%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.61%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.37%
MFS Research Bond Fund | 529B
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	B AND 529B
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%
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.76%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.71%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	574
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	850
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,151
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,875
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	174
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	550
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	951
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,875
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	3.27%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.43%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.25%
MFS Research Bond Fund | 529C
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	C AND 529C
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%
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.76%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.71%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	274
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	550
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	951
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,073
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	174
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	550
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	951
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,073
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	6.27%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.79%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.07%
MFS Research Bond Fund | R1
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	ALL R
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.66%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.66%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	169
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	525
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	904
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,969
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	7.38%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.90%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.16%
MFS Research Bond Fund | R2
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	ALL R
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.16%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.16%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	119
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	370
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	640
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,413
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	7.92%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.43%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.65%
MFS Research Bond Fund | R3
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	ALL R
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.91%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.91%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	93
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	291
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	506
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,124
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	8.19%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.67%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.97%
MFS Research Bond Fund | R4
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees, Column Name	rr_ShareholderFeesColumnName	ALL R
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
Operating Expenses, Column Name	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.16%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.66%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.66%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	68
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	212
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	370
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	$ 827
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	8.45%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	5.97%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	6.28%

[1] On shares purchased without an initial sales charge and redeemed within 24 months of purchase.

[2] MFS Fund Distributors, Inc. ("MFD"), has agreed in writing to waive the Class A and Class 529A service fee to 0.15% of the fund's average daily net assets annually until modified by a vote of the fund's Board of Trustees, but such agreement will continue until at least August 31, 2012. Assets attributable to Class B shares sold prior to May 1, 2006, are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, the fund's distributor, MFD, has agreed in writing to waive the Class B service fee to 0.15% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2012. The fund's distributor, MFD, has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on August 31, 2012, unless MFD elects to extend the waiver.