Risk/Return Detail Data - FidelitySAIRealEstateFundPro |
Sep. 29, 2025
USD ($)
|
|---|---|
| FidelitySAIRealEstateFundPro | Fidelity SAI Real Estate Fund | Fidelity SAI Real Estate Fund | |
| Prospectus Line Items | |
| Management Fees (as a percentage of Assets) | 0.50% |
| Distribution and Service (12b-1) Fees | 0.00% |
| Other Expenses (as a percentage of Assets): | 0.06% |
| Expenses (as a percentage of Assets) | 0.56% |
| Expense Example, with Redemption, 1 Year | $ 57 |
| Expense Example, with Redemption, 3 Years | 179 |
| Expense Example, with Redemption, 5 Years | 313 |
| Expense Example, with Redemption, 10 Years | $ 701 |
| FidelitySAIRealEstateFundPro | Fidelity SAI Real Estate Fund | |
| Prospectus Line Items | |
| Risk/Return [Heading] | Fund Summary Fund: Fidelity® SAI Real Estate Fund |
| Objective [Heading] | Investment Objective |
| Objective, Primary [Text Block] | 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. |
| Expense Heading [Optional Text] | Fee Table |
| Expense Narrative [Text Block] | The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. |
| Shareholder Fees Caption [Optional Text] | Shareholder fees |
| Shareholder Fee, Other | $ 0 |
| Operating Expenses Caption [Optional Text] | Annual Operating Expenses |
| Portfolio Turnover [Heading] | Portfolio Turnover |
| Portfolio Turnover [Text Block] | 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. For the period from September 4, 2024 to July 31, 2025, the fund's portfolio turnover rate was 15 % (annualized) of the average value of its portfolio. |
| Portfolio Turnover, Rate | 15.00% |
| Expense Example Narrative [Text Block] | 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: |
| Strategy [Heading] | Principal Investment Strategies |
| Strategy Narrative [Text Block] | 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. A real estate entity or real estate related investment is any company that is principally engaged in the real estate industry and includes commercial and residential mortgage-backed securities; debt securities of real estate entities; equity securities of entities whose primary assets are mortgage loans or commercial or residential mortgage-backed securities; REITs that either own properties or make construction loans and preferred stocks of REITs; real estate developers; companies with substantial real estate holdings; and other companies whose products and services are related to the real estate industry, such as building supply manufacturers, mortgage lenders, or mortgage servicing companies. The Adviser considers a company to be principally engaged in the real estate industry if (i) at least 50% of its assets, income, sales or profits are committed to, or derived from, the real estate industry, or (ii) a third party has given the company an industry or sector classification consistent with the real estate industry. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives. 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. |
| Strategy Portfolio Concentration [Text] | Normally investing at least 80% of assets in securities of companies principally engaged in the real estate industry and other real estate related investments. |
| Bar Chart and Performance Table [Heading] | Performance |
| Performance Narrative [Text Block] | Performance history will be available for the fund after the fund has been in operation for one calendar year. |
| Performance One Year or Less [Text] | Performance history will be available for the fund after the fund has been in operation for one calendar year. |
| Document Type | 485BPOS |
| Registrant Name | Fidelity Summer Street Trust |