0000225322 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member rr:RiskLoseMoneyMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member rr:RiskNondiversifiedStatusMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member rr:RiskNotInsuredDepositoryInstitutionMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:ForeignExposureMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:IssuerSpecificChangesMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:MidCapInvestingMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:RealEstateIndustryConcentrationMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:StockMarketVolatilityMember 2024-07-10 2024-07-10 0000225322 fmr:FidelitySAIRealEstateFund-PROMember fmr:S000085735Member fmr:C000251103Member 2024-07-10 2024-07-10 iso4217:USD pure shares 485BPOS 2023-07-31 false 0000225322 N-1A Fidelity Summer Street Trust Fund Summary Fund: Fidelity® SAI Real Estate Fund Investment Objective Fidelity® SAI Real Estate Fund seeks above-average income and long-term capital growth, consistent with reasonable investment risk. The fund seeks to provide a yield that exceeds the composite yield of the S&P 500 ® Index. Fee Table The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. Shareholder fees 0 Annual Operating Expenses 0.0050 0 0.0006 0.0056 Based on estimated amounts for the current fiscal year. This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated: 57 179 Portfolio Turnover 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 fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. Principal Investment Strategies Normally investing primarily in common stocks. Normally investing at least 80% of assets in securities of companies principally engaged in the real estate industry and other real estate related investments. Investing in domestic and foreign issuers. Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments. Normally investing at least 80% of assets in securities of companies principally engaged in the real estate industry and other real estate related investments. Principal Investment Risks Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments. Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry. The value of securities of issuers in the real estate industry can be affected by changes in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, and the management skill and creditworthiness of the issuer. Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. Mid Cap Investing. The value of securities of medium size, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers. In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund. An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency .   You could lose money by investing in the fund. Performance Performance history will be available for the fund after the fund has been in operation for one calendar year. Performance history will be available for the fund after the fund has been in operation for one calendar year. A Based on estimated amounts for the current fiscal year.