| Form N-CSR Cover | 6 Months Ended |
| Jul. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Fidelity Select Portfolios |
| Entity Central Index Key | 0000320351 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jul. 31, 2024 |
| Shareholder Report | 6 Months Ended |
| Jul. 31, 2024 USD ($) shares | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Fidelity Select Portfolios |
| Entity Central Index Key | 0000320351 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jul. 31, 2024 |
| Fidelity Telecom and Utilities Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Telecom and Utilities Fund |
| Class Name | Fidelity® Telecom and Utilities Fund |
| Trading Symbol | FIUIX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains information about Fidelity® Telecom and Utilities Fund for the period February 1, 2024 to July 31, 2024. |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last six months? (based on hypothetical $10,000 investment) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Telecom and Utilities Fund $ 0.74 % |
| Expenses Paid, Amount | $ 40 |
| Expense Ratio, Percent | 0.74% |
| Net Assets | $ 997,883,811 |
| Holdings Count | shares | 33 |
| Investment Company Portfolio Turnover | 46% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of July 31, 2024) KEY FACTS Fund Size $ Number of Holdings 33 Portfolio Turnover 46 % |
| Holdings [Text Block] | TOP INDUSTRIES (% of Fund's net assets) Electric Utilities 51.9 Diversified Telecommunication Services 24.0 Multi-Utilities 10.4 Wireless Telecommunication Services 6.0 Independent Power and Renewable Electricity Producers 3.9 Electrical Equipment 0.9 Gas Utilities 0.7 Capital Markets 0.2 Common Stocks 98.0 Short-Term Investments and Net Other Assets (Liabilities) 2.0 ASSET ALLOCATION (% of Fund's net assets) United States 99.0 United Kingdom 1.0 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Verizon Communications Inc 11.5 AT&T Inc 10.9 NextEra Energy Inc 10.3 PG&E Corp 7.4 Edison International 5.0 Southern Co/The 4.8 Sempra 4.8 Constellation Energy Corp 4.5 T-Mobile US Inc 4.5 Entergy Corp 4.0 67.7 |
| Shareholder Report, Holdings (Details) - Fidelity Telecom and Utilities Fund | Jul. 31, 2024 |
| TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.40% |
| TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.80% |
| TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.80% |
| TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| TI0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 51.90% |
| TI1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 24% |
| TI2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.40% |
| TI3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| TI4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| TI5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| TI6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| TI7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99% |
| United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98% |
| AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
