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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000356349_SupplementTextBlock
SUPPLEMENT TO PROSPECTUS

The date of this supplement is March 27, 2013.

MFS® Global Real Estate Fund

Effective immediately, the sub-section entitled "Performance Table" within the sub-heading entitled “Performance Information” beneath the main heading "Summary of Key Information" is restated in its entirety as follows:
Risk/Return [Heading] rr_RiskReturnHeading MFS® Global Real Estate Fund
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading 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-deferred 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-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.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (for the Periods Ended December 31, 2011)
FTSE EPRA/NAREIT Developed Real Estate Index
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Index Comparison (Reflects no deduction for fees, expenses or taxes) FTSE EPRA/NAREIT Developed Real Estate Index
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (5.82%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 33.50%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
A
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (12.55%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 27.30%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
A | After Taxes on Distributions
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns After Taxes on Distributions
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (13.61%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 20.31%
A | After Taxes on Distributions and Sale of Fund Shares
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (7.46%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 19.97%
B
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel B Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.32%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 28.39%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
C
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel C Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (8.69%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 29.07%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
I
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel I Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (6.89%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 30.35%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
R1
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel R1 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (7.81%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 29.07%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
R2
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel R2 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (7.35%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 29.71%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
R3
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel R3 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (7.12%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 30.03%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
R4
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel R4 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (6.89%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 30.35%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009
R5
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel R5 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (6.89%)
Average Annual Returns, Life rr_AverageAnnualReturnSinceInception 30.35%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 11, 2009