Risk/Return Detail Data - FidelityRealEstateIncomeFund-ETFClassPRO - USD ($) |
12 Months Ended | 60 Months Ended | 120 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 12, 2026 |
Jun. 12, 2026 |
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Jun. 12, 2026 |
Jun. 12, 2026 |
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| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | Fidelity Real Estate Income Fund - ETF Class | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Management Fees (as a percentage of Assets) | 0.53% | |||||||||||||||||
| Distribution and Service (12b-1) Fees | 0.00% | |||||||||||||||||
| Other Expenses (as a percentage of Assets): | [1] | 0.06% | ||||||||||||||||
| Expenses (as a percentage of Assets) | 0.59% | |||||||||||||||||
| Fee Waiver or Reimbursement | [2] | (0.02%) | ||||||||||||||||
| Net Expenses (as a percentage of Assets) | 0.57% | |||||||||||||||||
| Expense Example, with Redemption, 1 Year | $ 58 | |||||||||||||||||
| Expense Example, with Redemption, 3 Years | 186 | |||||||||||||||||
| Expense Example, with Redemption, 5 Years | 326 | |||||||||||||||||
| Expense Example, with Redemption, 10 Years | $ 735 | |||||||||||||||||
| Average Annual Return, Label [Optional Text] | Return Before Taxes | |||||||||||||||||
| Average Annual Return, Percent | 7.17% | 5.14% | 5.82% | |||||||||||||||
| Annual Return [Percent] | 7.17% | 7.93% | 9.32% | (14.54%) | 18.90% | (1.08%) | 17.91% | (0.64%) | 7.30% | 10.21% | ||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Risk/Return [Heading] | Fund Summary Fund /Class: Fidelity® Real Estate Income Fund /ETF Class | |||||||||||||||||
| Objective [Heading] | Investment Objective | |||||||||||||||||
| Objective, Primary [Text Block] | Fidelity® Real Estate Income Fund seeks higher than average income. As a secondary objective, the fund also seeks capital growth. | |||||||||||||||||
| 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's ETF Class. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. | |||||||||||||||||
| Shareholder Fees Caption [Optional Text] | Shareholder fees | |||||||||||||||||
| Shareholder Fee, Other | $ 0 | |||||||||||||||||
| Operating Expenses Caption [Optional Text] | Annual Operating Expenses | |||||||||||||||||
| Fee Waiver or Reimbursement over Assets, Date of Termination | Nov. 30, 2027 | |||||||||||||||||
| 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. During the most recent fiscal year, the fund's portfolio turnover rate was 24 % of the average value of its portfolio. | |||||||||||||||||
| Portfolio Turnover, Rate | 24.00% | |||||||||||||||||
| Other Expenses, New Fund, Based on Estimates [Text] | Based on estimated amounts for the current fiscal year. | |||||||||||||||||
| Expense Example Narrative [Text Block] | This example helps compare the cost of investing in the fund's ETF Class with the cost of investing in other funds or classes. Let's say, hypothetically, that the annual return for ETF Class shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund's ETF Class 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 ETF Class shares at the end of each time period indicated: | |||||||||||||||||
| Strategy [Heading] | Principal Investment Strategies | |||||||||||||||||
| Strategy Narrative [Text Block] | Normally investing at least 80% of assets in debt and income-producing equity securities of companies principally engaged in the real estate industry and other real estate related investments. Debt securities are used by issuers to borrow money. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Debt securities include corporate bonds, government securities (including Treasury securities), repurchase agreements, money market securities, mortgage and other asset-backed securities, loans and loan participations, and other securities, such as hybrids and synthetic securities, believed to have debt-like characteristics (e.g., securities classified as Tier 2 Regulatory capital, securities that rank above share capital in an insolvency waterfall, securities with maturity dates and non-cancellable interest payment structures). Equity securities represent an ownership interest, or the right to acquire an ownership interest, in an issuer. Equity securities include common stocks (including depositary receipts evidencing ownership of common stock), preferred stocks and other preferred securities, convertible securities, rights and warrants, and other securities, such as hybrid securities and trust preferred securities, believed to have equity-like characteristics. Income-producing equity securities are equity securities that pay, or are expected to pay within the next three months, dividends or interest. 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. 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. Normally investing primarily in preferred and common stocks of real estate investment trusts (REITs); debt securities of real estate entities; and commercial and other mortgage-backed securities, with an emphasis on lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Investing in domestic and foreign issuers. Using fundamental analysis of each issuer's financial condition and industry position and market and economic conditions to select investments. | |||||||||||||||||
| Bar Chart and Performance Table [Heading] | Performance | |||||||||||||||||
| Performance Narrative [Text Block] | The following information is intended to help you understand the risks of investing in the fund. The ETF Class shares are a new class of shares for which performance information is not available, and therefore, for periods prior to the inception of the ETF Class shares, the bar chart and table show performance information for the Fidelity® Real Estate Income Fund shares of the fund, a mutual fund class of shares of the fund not offered in this Prospectus. Returns of the ETF Class shares of the fund may vary from the returns of the Fidelity® Real Estate Income Fund shares due to differences in expenses. The information illustrates the changes in the performance of Fidelity® Real Estate Income Fund, a class of shares of the fund, from year to year and compares the performance of this class to the performance of a securities market index, a hypothetical composite of market indexes, and an additional index over various periods of time. The hypothetical composite of market indexes and additional index have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. Visit www.fidelity.com for more recent performance information for Fidelity® Real Estate Income Fund, a class of shares of the fund. Performance history will be available at www.fidelity.com for ETF Class after ETF Class has been in operation for one calendar year. | |||||||||||||||||
| Performance Information Illustrates Variability of Returns [Text] | The information illustrates the changes in the performance of Fidelity® Real Estate Income Fund, a class of shares of the fund, from year to year and compares the performance of this class to the performance of a securities market index, a hypothetical composite of market indexes, and an additional index over various periods of time. | |||||||||||||||||
| Performance One Year or Less [Text] | Performance history will be available at www.fidelity.com for ETF Class after ETF Class has been in operation for one calendar year. | |||||||||||||||||
| Performance Availability Website Address [Text] | www.fidelity.com | |||||||||||||||||
| Performance Past Does Not Indicate Future [Text] | Past performance (before and after taxes) is not an indication of future performance. | |||||||||||||||||
| Bar Chart [Heading] | Year-by-Year Returns | |||||||||||||||||
| Bar Chart, Returns for Class Not Offered in Prospectus [Text] | * The returns shown above are for Fidelity® Real Estate Income Fund, a class of shares of the fund that is not offered through this prospectus. ETF Class would have substantially similar annual returns to Fidelity® Real Estate Income Fund because the classes are invested in the same portfolio of securities. ETF Class's returns would differ from Fidelity® Real Estate Income Fund's returns only to the extent that the classes do not have the same expenses. | |||||||||||||||||
| Year to Date Return, Label [Optional Text] | Year-to-Date Return | |||||||||||||||||
| Bar Chart, Year to Date Return, Date | Mar. 31, 2026 | |||||||||||||||||
| Bar Chart, Year to Date Return | 0.41% | |||||||||||||||||
| Highest Quarterly Return, Label [Optional Text] | Highest Quarter Return | |||||||||||||||||
| Highest Quarterly Return, Date | Jun. 30, 2020 | |||||||||||||||||
| Highest Quarterly Return | 16.84% | |||||||||||||||||
| Lowest Quarterly Return, Label [Optional Text] | Lowest Quarter Return | |||||||||||||||||
| Lowest Quarterly Return, Date | Mar. 31, 2020 | |||||||||||||||||
| Lowest Quarterly Return | (25.55%) | |||||||||||||||||
| Performance Table Heading | Average Annual Returns | |||||||||||||||||
| Performance Table Uses Highest Federal Rate | After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. | |||||||||||||||||
| Performance Table Not Relevant to Tax Deferred | The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). | |||||||||||||||||
| Performance Table Explanation after Tax Higher | Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares. | |||||||||||||||||
| Performance Table Narrative | After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares. | |||||||||||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | After Taxes on Distributions | Fidelity Real Estate Income Fund - ETF Class | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Average Annual Return, Label [Optional Text] | Return After Taxes on Distributions | |||||||||||||||||
| Average Annual Return, Percent | 5.27% | 3.51% | 3.98% | |||||||||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | After Taxes on Distributions and Sales | Fidelity Real Estate Income Fund - ETF Class | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Average Annual Return, Label [Optional Text] | Return After Taxes on Distributions and Sale of Fund Shares | |||||||||||||||||
| Average Annual Return, Percent | 4.34% | 3.35% | 3.82% | |||||||||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | F0663 | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Average Annual Return, Label [Optional Text] | Fidelity Real Estate Income Composite Index℠ | |||||||||||||||||
| Average Annual Return, Percent | 5.81% | 2.11% | 4.01% | |||||||||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | ML038 | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Average Annual Return, Label [Optional Text] | ICE® BofA® US High Yield Constrained Index | |||||||||||||||||
| Average Annual Return, Percent | 8.50% | 4.50% | 6.44% | |||||||||||||||
| FidelityRealEstateIncomeFund-ETFClassPRO | Fidelity Real Estate Income Fund | LB091 | ||||||||||||||||||
| Prospectus Line Items | ||||||||||||||||||
| Average Annual Return, Label [Optional Text] | Bloomberg U.S. Universal Bond Index | |||||||||||||||||
| Average Annual Return, Percent | 7.58% | 0.06% | 2.44% | |||||||||||||||
| Document Type | 485BPOS | |||||||||||||||||
| Registrant Name | Fidelity Securities Fund | |||||||||||||||||
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