Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SELECT PORTFOLIOS
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary Fund:Communications Equipment Portfolio
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks capital appreciation.
Expense [Heading]	rr_ExpenseHeading	Fee Table
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees
(fees paid directly from your investment)	rr_ShareholderFeeOther	none
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Operating Expenses (expenses that you pay each year as a % of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	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 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 110% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	110.00%
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	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 your shareholder 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]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Normally investing primarily in common stocks. Normally investing at least 80% of assets in securities of companies principally engaged in the development, manufacture, or sale of communications equipment. 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. Proposed Reorganization. The Board of Trustees of Fidelity Select Portfolios has unanimously approved an Agreement and Plan of Reorganization ("Agreement") between Communications Equipment Portfolio and Computers Portfolio pursuant to which Communications Equipment Portfolio would be reorganized on a tax-free basis with and into Computers Portfolio. As a result of the proposed Reorganization, shareholders of Communications Equipment Portfolio would receive shares of Computers Portfolio. The Agreement provides for the transfer of all of the assets of Communications Equipment Portfolio in exchange for shares of Computers Portfolio equal in value to the net assets of Communications Equipment Portfolio and the assumption by Computers Portfolio of all of the liabilities of Communications Equipment Portfolio. After the exchange, Communications Equipment Portfolio will distribute the Computers Portfolio shares to its shareholders pro rata, in liquidation of Communications Equipment Portfolio. As a result, shareholders of Communications Equipment Portfolio will become shareholders of Computers Portfolio (these transactions are collectively referred to as the “Reorganization”). A Special Meeting (the “Meeting”) of the Shareholders of Communications Equipment Portfolio is expected to be held during the fourth quarter of 2021 and approval of the Agreement will be voted on at that time. A combined proxy statement and prospectus containing more information with respect to the Reorganization will be provided to shareholders of record of Communications Equipment Portfolio in advance of the meeting. If the Agreement is approved at the Meeting and certain conditions required by the Agreement are satisfied, the Reorganization is expected to take place on or about November 12, 2021. If shareholder approval of the Agreement is delayed due to failure to meet a quorum or otherwise, the Reorganization will become effective, if approved, as soon as practicable thereafter. In connection with seeking shareholder approval of the Agreement, effective the close of business on June 7, 2021, new positions in Communications Equipment Portfolio (the fund) may no longer be opened. Shareholders of the fund on that date may continue to add to their fund positions existing on that date. Investors who did not own shares of the fund on June 7, 2021 generally will not be allowed to buy shares of the fund except that new fund positions may be opened: 1) by participants in most group employer retirement plans (and their successor plans) if a qualifying fund is already established as an investment option under the plans (or under another plan sponsored by the same employer) , 2) by participants in a 401(a) plan covered by a master record keeping services agreement between Fidelity and a national federation of employers that included a qualifying fund as a core investment option , 3) for accounts managed on a discretionary basis by certain registered investment advisers that have discretionary assets of at least $500 million invested in mutual funds and already included the fund in their discretionary account program , 4) by a mutual fund or a qualified tuition program for which Fidelity serves as investment manager, 5) by a portfolio manager of the fund, and 6) by a fee deferral plan offered to trustees of certain Fidelity funds, if the fund is an investment option under the plan. These restrictions generally will apply to investments made directly with Fidelity and investments made through intermediaries. Investors may be required to demonstrate eligibility to buy shares of the fund before an investment is accepted. The foregoing is not a solicitation of any proxy. For a free copy of the Proxy Statement describing the Reorganization (and containing important information about fees, expenses and risk considerations) and a Prospectus for Computers Portfolio, please call 1-800-544-8544. The prospectus/proxy statement will also be available for free on the Securities and Exchange Commission’s web site (www.sec.gov).
Strategy Portfolio Concentration [Text]	rr_StrategyPortfolioConcentration	Normally investing at least 80% of assets in securities of companies principally engaged in the development, manufacture, or sale of communications equipment.
Risk [Heading]	rr_RiskHeading	Principal Investment Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. Communications Equipment Industry Concentration. The communications equipment industry can be significantly affected by failure to obtain, or delays in obtaining, financing or regulatory approval, intense competition, product compatibility, consumer preferences, corporate capital expenditures, and rapid obsolescence. 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. The value of securities of smaller issuers can be more volatile than that of larger issuers. High Portfolio Turnover. High portfolio turnover (more than 100%) may result in increased transaction costs and potentially higher capital gains or losses. The effects of higher than normal portfolio turnover may adversely affect the fund's performance. 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.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money by investing in the fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	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.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	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.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time. The indexes 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.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.fidelity.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]	rr_BarChartHeading	Year-by-Year Returns
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Returns
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	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	rr_PerformanceTableNotRelevantToTaxDeferred	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	rr_PerformanceTableExplanationAfterTaxHigher	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	rr_PerformanceTableNarrativeTextBlock	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.
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | Communications Equipment Portfolio-Default
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.53%
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.34%
Total annual operating expenses	rr_ExpensesOverAssets	0.87%
1 year	rr_ExpenseExampleYear01	$ 89
3 years	rr_ExpenseExampleYear03	278
5 years	rr_ExpenseExampleYear05	482
10 years	rr_ExpenseExampleYear10	$ 1,073
2011	rr_AnnualReturn2011	(16.68%)
2012	rr_AnnualReturn2012	5.97%
2013	rr_AnnualReturn2013	28.16%
2014	rr_AnnualReturn2014	14.97%
2015	rr_AnnualReturn2015	(10.18%)
2016	rr_AnnualReturn2016	19.88%
2017	rr_AnnualReturn2017	11.66%
2018	rr_AnnualReturn2018	3.95%
2019	rr_AnnualReturn2019	6.09%
2020	rr_AnnualReturn2020	8.35%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year-to-Date Return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2021
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	12.45%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Highest Quarter Return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2020
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	18.92%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Lowest Quarter Return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.14%)
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | Return Before Taxes | Communications Equipment Portfolio-Default
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
Past 1 year	rr_AverageAnnualReturnYear01	8.35%
Past 5 years	rr_AverageAnnualReturnYear05	9.85%
Past 10 years	rr_AverageAnnualReturnYear10	6.45%
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | After Taxes on Distributions | Communications Equipment Portfolio-Default
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
Past 1 year	rr_AverageAnnualReturnYear01	8.25%
Past 5 years	rr_AverageAnnualReturnYear05	9.00%
Past 10 years	rr_AverageAnnualReturnYear10	5.70%
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | After Taxes on Distributions and Sales | Communications Equipment Portfolio-Default
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	rr_AverageAnnualReturnYear01	5.02%
Past 5 years	rr_AverageAnnualReturnYear05	7.71%
Past 10 years	rr_AverageAnnualReturnYear10	5.02%
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | SP001
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	S&P 500® Index
Past 1 year	rr_AverageAnnualReturnYear01	18.40%
Past 5 years	rr_AverageAnnualReturnYear05	15.22%
Past 10 years	rr_AverageAnnualReturnYear10	13.88%
02.28 Select Portfolios: Group 7 Information Technology Sector Combo PRO-21 | Communications Equipment Portfolio | F1530
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	MSCI North America IMI + ADR Custom Communications Equipment 25/50 Linked Index
Past 1 year	rr_AverageAnnualReturnYear01	9.47%
Past 5 years	rr_AverageAnnualReturnYear05	9.04%
Past 10 years	rr_AverageAnnualReturnYear10	5.89%