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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
ProspectusDate rr_ProspectusDate May 24, 2011
MFS New Discovery Value Fund (Prospectus Summary) | MFS New Discovery Value 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 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. The annual fund operating expenses are based on
estimated expenses for the current fiscal year expressed as a percentage of the
fund's estimated average net assets during the period.

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 6 of the fund's prospectus and "Waivers of Sales Charges" on page 11 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.
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. 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 6 of the fund's prospectus and "Waivers of Sales Charges" on page 11 of the fund's statement of additional information Part I.
Expense Breakpoint, Minimum Investment Required Amount rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates rr_OtherExpensesNewFundBasedOnEstimates The annual fund operating expenses are based on estimated expenses for the current fiscal year expressed as a percentage of the fund's estimated average net assets during the period.
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 the fund's assets primarily in equity securities. Equity
securities include common stocks, preferred stocks, securities convertible into
stocks, and depositary receipts for those securities.

MFS focuses on investing the fund's assets in the stocks of companies it
believes are undervalued compared to their perceived worth (value companies).

While MFS may invest the fund's assets in companies of any size, MFS generally
focuses on companies with small capitalizations.

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

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 issuers and their potential in light of their current financial
condition, and market, economic, political, and regulatory conditions. Factors
considered may include analysis of an issuer's earnings, cash flows, competitive
position, and management ability. Quantitative models that systematically
evaluate an issuer's valuation, price and earnings momentum, earnings quality,
and other factors 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:

Stock Market/Company Risk:  Stock markets are volatile and can decline
significantly in response to issuer, market, economic, industry, political,
regulatory, geopolitical, and other conditions, as well as to investor
perceptions of these conditions. The price of an equity security can decrease
significantly in response to these conditions, and these conditions can affect a
single issuer or type of security, issuers within a broad market sector,
industry or geographic region, or the market in general.

Value Company Risk:  The stocks of value companies can continue to be
undervalued for long periods of time and not realize their expected value and
can be more volatile than the market in general.

Small Cap Risk:  The stocks of small cap companies can be more volatile than
stocks of larger companies.

Foreign Risk:  Exposure to foreign 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.

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.

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.

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.
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 are not included because the fund has not
had a full calendar year of investment operations.
Performance, One Year or Less rr_PerformanceOneYearOrLess The bar chart and performance table are not included because the fund has not had a full calendar year of investment operations.
MFS New Discovery Value 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 5.75%
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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.36%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 706
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 981
MFS New Discovery Value Fund | B
  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees, Column Name rr_ShareholderFeesColumnName 
B
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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.11%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 614
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 961
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 214
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 661
MFS New Discovery Value Fund | C
  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees, Column Name rr_ShareholderFeesColumnName 
C
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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.11%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 314
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 661
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 214
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 661
MFS New Discovery Value Fund | I
  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees, Column Name rr_ShareholderFeesColumnName 
I
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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.11%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 113
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 353
MFS New Discovery Value 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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.11%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 214
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 661
MFS New Discovery Value 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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.61%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 164
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 508
MFS New Discovery Value 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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.36%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 138
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 431
MFS New Discovery Value 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 0.90%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.11%
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 113
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 $ 353
[1] On shares purchased without an initial sales charge and redeemed within 24 months of purchase.