Prospectus [Table] Risk/Return: Document Type Document Period End Date Registrant Name Entity Central Index Key Amendment Flag Amendment Description Trading Symbol Document Creation Date Document Effective Date Entity Investment Company Type Prospectus Date Document [Axis] Prospectus Performance Measure [Axis] Before Taxes Series [Axis] Series Class [Axis] Average Annual Return, Percent Annual Return [Percent] Share Classes Risk/Return [Heading] Objective [Heading] Objective, Primary [Text Block] Objective, Secondary [Text Block] Expense Heading [Optional Text] Expense Narrative [Text Block] Shareholder Fees Caption [Optional Text] Shareholder Fees [Table] Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses [Table] Expense Footnotes [Text Block] Expenses Deferred Charges [Text Block] Expenses Range of Exchange Fees [Text Block] Expense Example [Heading] Expense Example by Year [Heading] Expense Example Narrative [Text Block] Expense Example by, Year, Caption [Text] Expense Example, With Redemption [Table] Expense Example, No Redemption Narrative [Text Block] Expense Example, No Redemption, By Year, Caption [Text] Expense Example, No Redemption [Table] Expense Example Footnotes [Text Block] Expense Example Closing [Text Block] Portfolio Turnover [Heading] Portfolio Turnover [Text Block] Strategy [Heading] Strategy Narrative [Text Block] Risk [Text Block] Bar Chart and Performance Table [Heading] Performance Narrative [Text Block] Bar Chart Narrative [Text Block] Bar Chart [Heading] Bar Chart [Table] Bar Chart Footnotes [Text Block] Bar Chart Closing [Text Block] Performance Table Heading Performance Table Narrative Performance [Table] Market Index Performance [Table] Performance Table Footnotes Performance Table Closing [Text Block] Supplement to Prospectus [Text Block] Shareholder Fees: Shareholder Fees Column [Optional Text] Operating Expenses: Operating Expenses Column [Optional Text] Expense Example: Expense Example, By Year, Column [Optional Text] Expense Example, No Redemption: Expense Example, No Redemption, By Year, Column [Optional Text] Bar Chart Table: Annual Return Caption [Text] Annual Return, Column [Optional Text] Annual Return, Inception Date Average Annual Return: Fee Waiver or Reimbursement over Assets, Date of Termination Portfolio Turnover, Rate Expense Breakpoint Discounts [Text] Expense Breakpoint, Minimum Investment Required [Amount] Expenses Represent Both Master and Feeder [Text] Expenses Explanation of Nonrecurring Account Fee [Text] Other Expenses, New Fund, Based on Estimates [Text] Acquired Fund Fees and Expenses, Based on Estimates [Text] Expenses Other Expenses Had Extraordinary Expenses Been Included [Text] Expenses Restated to Reflect Current [Text] Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] Strategy Portfolio Concentration [Text] Risk Lose Money [Member] Risk Nondiversified Status [Member] Risk Money Market Fund Price Fluctuates [Member] Risk Money Market Fund May Impose Fees or Suspend Sales [Member] Risk Money Market Fund Sponsor May Not Provide Support [Member] Risk Money Market Fund May Not Preserve Dollar [Member] Risk Not Insured [Member] Risk Not Insured Depository Institution [Member] Performance Information Illustrates Variability of Returns [Text] Performance One Year or Less [Text] Performance Additional Market Index [Text] Performance Availability Phone [Text] Performance Availability Website Address [Text] Performance Past Does Not Indicate Future [Text] Bar Chart Does Not Reflect Sales Loads [Text] Bar Chart, Reason Selected Class Different from Immediately Preceding Period [Text] Bar Chart, Returns for Class Not Offered in Prospectus [Text] Year to Date Return, Label [Optional Text] Bar Chart, Year to Date Return, Date Bar Chart, Year to Date Return Highest Quarterly Return, Label [Optional Text] Highest Quarterly Return, Date Highest Quarterly Return Lowest Quarterly Return, Label [Optional Text] Lowest Quarterly Return, Date Lowest Quarterly Return Performance Table Does Reflect Sales Loads Performance Table Market Index Changed Index No Deduction for Fees, Expenses, or Taxes [Text] Performance Table Uses Highest Federal Rate Performance Table Not Relevant to Tax Deferred Performance Table One Class of after Tax Shown [Text] Performance Table Explanation after Tax Higher Performance Table Footnotes, Reason Performance Information for Class Different from Immediately Preceding Period [Text] Average Annual Return, Caption [Optional Text] Average Annual Return, Column Name [Optional Text] Average Annual Return, Label [Optional Text] Money Market Seven Day Yield, Caption [Optional Text] Money Market Seven Day Yield Column [Optional Text] Money Market Seven Day Yield Phone Money Market Seven Day Yield Money Market Seven Day Tax Equivalent Yield Thirty Day Yield Caption [Optional Text] Thirty Day Yield Column [Optional Text] Thirty Day Yield Phone Thirty Day Yield Thirty Day Tax Equivalent Yield Expense Example, with Redemption, 1 Year Expense Example, with Redemption, 3 Years Expense Example, with Redemption, 5 Years Expense Example, with Redemption, 10 Years Expense Example, No Redemption, 1 Year Expense Example, No Redemption, 3 Years Expense Example, No Redemption, 5 Years Expense Example, No Redemption, 10 Years FidelityEquityMarketNeutralFund-AMCIZPro FidelityEquityMarketNeutralFund-AMCIZPro FidelityHedgedEquityFund-RetailPRO FidelityHedgedEquityFund-RetailPRO FidelityHedgedEquityFund-AMCIZPRO FidelityHedgedEquityFund-AMCIZPRO FidelityMacroOpportunitiesRiskParityFunds-AMCIZComboPRO FidelityMacroOpportunitiesRiskParityFunds-AMCIZComboPRO FidelitySAIMergerArbitrageFund-PRO FidelitySAIMergerArbitrageFund-PRO FidelityMacroOpportunitiesRiskParityFunds-RetailComboPRO FidelityMacroOpportunitiesRiskParityFunds-RetailComboPRO FidelitySAIConvertibleArbitrageFund-PRO FidelitySAIConvertibleArbitrageFund-PRO FidelitySAIManagedFuturesFund-PRO FidelitySAIManagedFuturesFund-PRO FidelityEquityMarketNeutralFund-RetailPRO FidelityEquityMarketNeutralFund-RetailPRO Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Risk Parity Fund Fidelity Risk Parity Fund Fidelity Risk Parity Fund Fidelity SAI Convertible Arbitrage Fund Fidelity SAI Convertible Arbitrage Fund Fidelity SAI Convertible Arbitrage Fund Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Managed Futures Fund Fidelity SAI Managed Futures Fund Fidelity SAI Managed Futures Fund Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Hedged Equity Fund Fidelity Advisor Hedged Equity Fund - Class A Fidelity Advisor Hedged Equity Fund - Class A Fidelity Advisor Hedged Equity Fund - Class A Fidelity Hedged Equity Fund Fidelity Advisor Hedged Equity Fund - Class M Fidelity Advisor Hedged Equity Fund - Class M Fidelity Advisor Hedged Equity Fund - Class M Fidelity Hedged Equity Fund Fidelity Advisor Hedged Equity Fund - Class C Fidelity Advisor Hedged Equity Fund - Class C Fidelity Advisor Hedged Equity Fund - Class C Fidelity Hedged Equity Fund Fidelity Advisor Hedged Equity Fund - Class I Fidelity Advisor Hedged Equity Fund - Class I Fidelity Advisor Hedged Equity Fund - Class I Fidelity Hedged Equity Fund Fidelity Advisor Hedged Equity Fund - Class Z Fidelity Advisor Hedged Equity Fund - Class Z Fidelity Advisor Hedged Equity Fund - Class Z Fidelity Risk Parity Fund Fidelity Risk Parity Fund Fidelity Risk Parity Fund Fidelity Risk Parity Fund Fidelity SAI Convertible Arbitrage Fund Fidelity SAI Convertible Arbitrage Fund Fidelity SAI Convertible Arbitrage Fund Fidelity SAI Convertible Arbitrage Fund Fidelity Risk Parity Fund Fidelity Advisor Risk Parity Fund - Class A Fidelity Advisor Risk Parity Fund - Class A Fidelity Advisor Risk Parity Fund - Class A Fidelity Risk Parity Fund Fidelity Advisor Risk Parity Fund - Class M Fidelity Advisor Risk Parity Fund - Class M Fidelity Advisor Risk Parity Fund - Class M Fidelity Risk Parity Fund Fidelity Advisor Risk Parity Fund - Class C Fidelity Advisor Risk Parity Fund - Class C Fidelity Advisor Risk Parity Fund - Class C Fidelity Risk Parity Fund Fidelity Advisor Risk Parity Fund - Class I Fidelity Advisor Risk Parity Fund - Class I Fidelity Advisor Risk Parity Fund - Class I Fidelity Risk Parity Fund Fidelity Advisor Risk Parity Fund - Class Z Fidelity Advisor Risk Parity Fund - Class Z Fidelity Advisor Risk Parity Fund - Class Z Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity Equity Market Neutral Fund Fidelity Advisor Equity Market Neutral Fund - Class A Fidelity Advisor Equity Market Neutral Fund - Class A Fidelity Advisor Equity Market Neutral Fund - Class A Fidelity Equity Market Neutral Fund Fidelity Advisor Equity Market Neutral Fund - Class M Fidelity Advisor Equity Market Neutral Fund - Class M Fidelity Advisor Equity Market Neutral Fund - Class M Fidelity Equity Market Neutral Fund Fidelity Advisor Equity Market Neutral Fund - Class C Fidelity Advisor Equity Market Neutral Fund - Class C Fidelity Advisor Equity Market Neutral Fund - Class C Fidelity Equity Market Neutral Fund Fidelity Advisor Equity Market Neutral Fund - Class I Fidelity Advisor Equity Market Neutral Fund - Class I Fidelity Advisor Equity Market Neutral Fund - Class I Fidelity Equity Market Neutral Fund Fidelity Advisor Equity Market Neutral Fund - Class Z Fidelity Advisor Equity Market Neutral Fund - Class Z Fidelity Advisor Equity Market Neutral Fund - Class Z Fidelity SAI Merger Arbitrage Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Merger Arbitrage Fund Fidelity SAI Managed Futures Fund Fidelity SAI Managed Futures Fund Fidelity SAI Managed Futures Fund Fidelity SAI Managed Futures Fund IXUYK IXUYK IXUYK SP001 SP001 SP001 IXWWB IXWWB IXWWB IXSSC IXSSC IXSSC MS159 MS159 MS159 LB057 LB057 LB057 LB001 LB001 LB001 OptionsRiskMember OptionsRiskMember OptionsRiskMember AssetAllocationRiskMember AssetAllocationRiskMember AssetAllocationRiskMember CurrencyExposureMember CurrencyExposureMember CurrencyExposureMember SubsidiaryRiskMember SubsidiaryRiskMember SubsidiaryRiskMember ConvertibleArbitrageStrategyMember ConvertibleArbitrageStrategyMember ConvertibleArbitrageStrategyMember InterestRateChangesMember InterestRateChangesMember InterestRateChangesMember ContractsForDifferenceCfdRiskMember ContractsForDifferenceCfdRiskMember ContractsForDifferenceCfdRiskMember QuantitativeInvestingMember QuantitativeInvestingMember QuantitativeInvestingMember ForeignCurrencyTransactionsMember ForeignCurrencyTransactionsMember ForeignCurrencyTransactionsMember ShortSalesAndLeverageRiskMember ShortSalesAndLeverageRiskMember ShortSalesAndLeverageRiskMember CommodityLinkedInvestingMember CommodityLinkedInvestingMember CommodityLinkedInvestingMember MergerArbitrageStrategyMember MergerArbitrageStrategyMember MergerArbitrageStrategyMember FuturesContractRiskMember FuturesContractRiskMember FuturesContractRiskMember PrepaymentMember PrepaymentMember PrepaymentMember MidCapInvestingMember MidCapInvestingMember MidCapInvestingMember USGovernmentObligationsRiskMember USGovernmentObligationsRiskMember USGovernmentObligationsRiskMember GeographicExposureToEuropeMember GeographicExposureToEuropeMember GeographicExposureToEuropeMember SpecialPurposeAcquisitionCompaniesRiskSpacRiskMember SpecialPurposeAcquisitionCompaniesRiskSpacRiskMember SpecialPurposeAcquisitionCompaniesRiskSpacRiskMember InvestingInExchangeTradedFundsEtfsAndEtnsMember InvestingInExchangeTradedFundsEtfsAndEtnsMember InvestingInExchangeTradedFundsEtfsAndEtnsMember ForeignAndEmergingMarketsRiskMember ForeignAndEmergingMarketsRiskMember ForeignAndEmergingMarketsRiskMember LeverageRiskMember LeverageRiskMember LeverageRiskMember InvestingInOtherFundsMember InvestingInOtherFundsMember InvestingInOtherFundsMember IssuerSpecificChangesMember IssuerSpecificChangesMember IssuerSpecificChangesMember StockMarketVolatilityMember StockMarketVolatilityMember StockMarketVolatilityMember SmallCapInvestingMember SmallCapInvestingMember SmallCapInvestingMember CommodityFuturesMember CommodityFuturesMember CommodityFuturesMember CorrelationRiskMember CorrelationRiskMember CorrelationRiskMember HighPortfolioTurnoverMember HighPortfolioTurnoverMember HighPortfolioTurnoverMember InvestingInEtfsAndEtnsMember InvestingInEtfsAndEtnsMember InvestingInEtfsAndEtnsMember ForeignExposureMember ForeignExposureMember ForeignExposureMember SwapsRiskMember SwapsRiskMember SwapsRiskMember Shareholder Fee, Other Management Fees (as a percentage of Assets) Distribution and Service (12b-1) Fees Other Expenses (as a percentage of Assets): Acquired Fund Fees and Expenses Expenses (as a percentage of Assets) Fee Waiver or Reimbursement Net Expenses (as a percentage of Assets) After Taxes on Distributions After Taxes on Distributions and Sales Redemption Fee Redemption Fee (as a percentage of Amount Redeemed) Maximum Cumulative Sales Charge (as a percentage of Offering Price) Maximum Deferred Sales Charge (as a percentage) Risk [Axis] All Risks [Member]