v3.26.1
Risk/Return Detail Data - FidelitySeriesLargeCapValueIndexFund-PRO - USD ($)
 12 Months Ended 36 Months Ended 48 Months Ended 60 Months Ended 96 Months Ended 120 Months Ended
Apr. 01, 2026
Apr. 01, 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
Apr. 01, 2026
Apr. 01, 2026
Apr. 01, 2026
Apr. 01, 2026
Apr. 01, 2026
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund | Fidelity Series Large Cap Value Index Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.00%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.00%                                
Expenses (as a percentage of Assets) 0.00%                                
Expense Example, with Redemption, 1 Year $ 0                                
Expense Example, with Redemption, 3 Years 0                                
Expense Example, with Redemption, 5 Years 0                                
Expense Example, with Redemption, 10 Years $ 0                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   15.89%                         11.35%   10.55%
Annual Return [Percent]     15.89% 14.35% 11.59% (7.53%) 25.19% 2.86% 26.60% (8.23%) 13.68% 17.19%          
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® Series Large Cap Value Index Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® Series Large Cap Value Index Fund seeks to provide investment results that correspond to the total return of stocks of large capitalization United States companies.                                
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. During the most recent fiscal year, the fund's portfolio turnover rate was 17 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 17.00%                                
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 at least 80% of assets in securities of companies in the Russell 1000® Value Index. The Russell 1000 ® Value Index is a market capitalization-weighted index designed to measure the performance of the large-cap value segment of the U.S. equity market. It includes those Russell 1000 ® Index companies with lower price-to-book ratios and lower expected growth rates. The stocks of these companies are often called "value" stocks. Effective March 24, 2025, the Russell 1000 ® Value Index applies a capping methodology. Index constituents are capped quarterly so that no more than 22.5% of the index weight may be allocated to a single constituent, and the sum of the weights of all constituents representing more than 4.5% of the index should not exceed 45% of the total index weight. For periods prior to March 24, 2025, the index was uncapped. 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. Lending securities to earn income for the fund.                                
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 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 additional index has 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. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.                                
Performance Information Illustrates Variability of Returns [Text] 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] 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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2020                                
Highest Quarterly Return 16.24%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Mar. 31, 2020                                
Lowest Quarterly Return (26.69%)                                
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.                                
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund | After Taxes on Distributions | Fidelity Series Large Cap Value Index Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   14.84%                         10.07%   9.33%
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund | After Taxes on Distributions and Sales | Fidelity Series Large Cap Value Index Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   10.03%                         8.69%   8.29%
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund | RS005                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Russell 1000® Value Index                              
Average Annual Return, Percent   15.91%                         11.33%   10.53%
FidelitySeriesLargeCapValueIndexFund-PRO | Fidelity Series Large Cap Value Index Fund | RS001                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Russell 1000® Index                              
Average Annual Return, Percent   17.37%                         13.59%   14.59%
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | Fidelity SAI Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.20%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.01%                                
Expenses (as a percentage of Assets) 0.21%                                
Fee Waiver or Reimbursement [1] (0.01%)                                
Net Expenses (as a percentage of Assets) 0.20%                                
Expense Example, with Redemption, 1 Year $ 20                                
Expense Example, with Redemption, 3 Years 66                                
Expense Example, with Redemption, 5 Years 117                                
Expense Example, with Redemption, 10 Years $ 266                                
Annual Return, Inception Date Nov. 06, 2023                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   3.26%                     3.60% [2]        
Annual Return [Percent]     3.26% 3.30%                          
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® SAI Conservative Income Municipal Bond Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® SAI Conservative Income Municipal Bond Fund seeks to provide a high level of income, exempt from federal income tax, consistent with preservation of capital.                                
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                                
Fee Waiver or Reimbursement over Assets, Date of Termination May 31, 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 64 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 64.00%                                
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 at least 80% of assets in U.S. dollar-denominated municipal money market securities and high quality investment-grade municipal debt securities whose interest is exempt from federal income tax. Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Municipal money market securities are high-quality, short-term debt securities that pay a fixed, variable, or floating interest rate, and include variable rate demand notes, commercial paper, and municipal notes. Municipal securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. High quality investment grade securities in which the fund invests include securities or issuers (i) rated at least A- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO) or similarly rated by the Adviser, and (ii) for securities with a credit maturity within one year, rated at least BBB or its equivalent by all NRSROs that rate the security and similarly rated by the Adviser. 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. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). Normally maintaining a dollar-weighted average maturity of one year or less. Normally investing in securities with a maximum maturity of four years. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities 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 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, 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.                                
Performance Information Illustrates Variability of Returns [Text] 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, a hypothetical composite of market indexes, and an additional index over various periods of time.                                
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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Sep. 30, 2024                                
Highest Quarterly Return 1.25%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Dec. 31, 2024                                
Lowest Quarterly Return 0.55%                                
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 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. 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.                                
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | After Taxes on Distributions | Fidelity SAI Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   3.26%                     3.59% [2]        
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | After Taxes on Distributions and Sales | Fidelity SAI Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   3.17%                     3.53% [2]        
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                     5.58%        
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | LB319                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond 1 Year (1-2 Y) Index                              
Average Annual Return, Percent   3.47%                     3.63%        
FidelitySAIConservativeIncomeMunicipalBondFund-PRO | Fidelity SAI Conservative Income Municipal Bond Fund | F1872                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Fidelity Conservative Income Municipal Bond Composite Index℠                              
Average Annual Return, Percent   3.16%                     3.41%        
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class A                                  
Prospectus Line Items                                  
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 4.00%                                
Maximum Deferred Sales Charge (as a percentage) [3] 0.00%                                
Management Fees (as a percentage of Assets) 0.48%                                
Distribution and Service (12b-1) Fees 0.25%                                
Other Expenses (as a percentage of Assets): 0.83%                                
Expenses (as a percentage of Assets) 1.56%                                
Fee Waiver or Reimbursement [4] (0.94%)                                
Net Expenses (as a percentage of Assets) 0.62%                                
Expense Example, with Redemption, 1 Year $ 461                                
Expense Example, with Redemption, 3 Years 753                                
Expense Example, with Redemption, 5 Years 1,100                                
Expense Example, with Redemption, 10 Years 2,078                                
Expense Example, No Redemption, 1 Year 461                                
Expense Example, No Redemption, 3 Years 753                                
Expense Example, No Redemption, 5 Years 1,100                                
Expense Example, No Redemption, 10 Years $ 2,078                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   0.94%                       2.32% [5]      
Annual Return [Percent]     5.15% 1.02% 5.99%                        
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class M                                  
Prospectus Line Items                                  
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 4.00%                                
Maximum Deferred Sales Charge (as a percentage) [3] 0.00%                                
Management Fees (as a percentage of Assets) 0.51%                                
Distribution and Service (12b-1) Fees 0.25%                                
Other Expenses (as a percentage of Assets): 0.87%                                
Expenses (as a percentage of Assets) 1.63%                                
Fee Waiver or Reimbursement [4] (1.01%)                                
Net Expenses (as a percentage of Assets) 0.62%                                
Expense Example, with Redemption, 1 Year $ 461                                
Expense Example, with Redemption, 3 Years 765                                
Expense Example, with Redemption, 5 Years 1,127                                
Expense Example, with Redemption, 10 Years 2,145                                
Expense Example, No Redemption, 1 Year 461                                
Expense Example, No Redemption, 3 Years 765                                
Expense Example, No Redemption, 5 Years 1,127                                
Expense Example, No Redemption, 10 Years $ 2,145                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   0.94%                       2.32% [6]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class C                                  
Prospectus Line Items                                  
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                                
Maximum Deferred Sales Charge (as a percentage) [7] 1.00%                                
Management Fees (as a percentage of Assets) 0.52%                                
Distribution and Service (12b-1) Fees 1.00%                                
Other Expenses (as a percentage of Assets): 0.82%                                
Expenses (as a percentage of Assets) 2.34%                                
Fee Waiver or Reimbursement [4] (0.97%)                                
Net Expenses (as a percentage of Assets) 1.37%                                
Expenses Deferred Charges [Text Block] On Class C shares redeemed less than one year after purchase.                                
Expense Example, with Redemption, 1 Year $ 239                                
Expense Example, with Redemption, 3 Years 605                                
Expense Example, with Redemption, 5 Years 1,131                                
Expense Example, with Redemption, 10 Years 2,378                                
Expense Example, No Redemption, 1 Year 139                                
Expense Example, No Redemption, 3 Years 605                                
Expense Example, No Redemption, 5 Years 1,131                                
Expense Example, No Redemption, 10 Years $ 2,378                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   3.36%                       2.69% [8]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class I                                  
Prospectus Line Items                                  
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                                
Maximum Deferred Sales Charge (as a percentage) 0.00%                                
Management Fees (as a percentage of Assets) 0.52%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.80%                                
Expenses (as a percentage of Assets) 1.32%                                
Fee Waiver or Reimbursement [4] (0.95%)                                
Net Expenses (as a percentage of Assets) 0.37%                                
Expense Example, with Redemption, 1 Year $ 38                                
Expense Example, with Redemption, 3 Years 291                                
Expense Example, with Redemption, 5 Years 600                                
Expense Example, with Redemption, 10 Years 1,477                                
Expense Example, No Redemption, 1 Year 38                                
Expense Example, No Redemption, 3 Years 291                                
Expense Example, No Redemption, 5 Years 600                                
Expense Example, No Redemption, 10 Years $ 1,477                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   5.31%                       3.71% [9]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class Z                                  
Prospectus Line Items                                  
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                                
Maximum Deferred Sales Charge (as a percentage) 0.00%                                
Management Fees (as a percentage of Assets) 0.39%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.70%                                
Expenses (as a percentage of Assets) 1.09%                                
Fee Waiver or Reimbursement [4] (0.78%)                                
Net Expenses (as a percentage of Assets) 0.31%                                
Expense Example, with Redemption, 1 Year $ 32                                
Expense Example, with Redemption, 3 Years 242                                
Expense Example, with Redemption, 5 Years 498                                
Expense Example, with Redemption, 10 Years 1,234                                
Expense Example, No Redemption, 1 Year 32                                
Expense Example, No Redemption, 3 Years 242                                
Expense Example, No Redemption, 5 Years 498                                
Expense Example, No Redemption, 10 Years $ 1,234                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   5.37%                       3.77% [10]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund /Class: Fidelity® Sustainable Intermediate Municipal Income Fund /Fidelity Advisor® Sustainable Intermediate Municipal Income Fund A, M, C, I, Z                                  
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® Sustainable Intermediate Municipal Income Fund seeks as high a level of current income, exempt from federal income tax, as is consistent with the preservation of capital.                                
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. 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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 39 of the prospectus and in the sales charge waiver appendix to the prospectus.                                
Shareholder Fees Caption [Optional Text] Shareholder fees                                
Operating Expenses Caption [Optional Text] Annual Operating Expenses                                
Fee Waiver or Reimbursement over Assets, Date of Termination May 31, 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 16 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 16.00%                                
Expenses Deferred Charges [Text Block] Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 0.75% and 0.25%, respectively.                                
Expense Breakpoint Discounts [Text] You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 39 of the prospectus                                
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000                                
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 and if you hold your shares:                                
Strategy [Heading] Principal Investment Strategies                                
Strategy Narrative [Text Block] Normally investing at least 80% of assets in municipal securities (i) whose interest is exempt from federal income tax and (ii) that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have positive environmental, social and governance (ESG) characteristics. The municipal securities in which the fund invests are normally investment-grade (those of medium and high quality). Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. 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. Evaluating each security in which the fund invests using both a traditional municipal bond credit, structure and relative value analysis and a consideration of the Adviser's judgment about the security's ESG characteristics. When assessing a security's ESG characteristics and its eligibility for purchase, the Adviser considers the following, where available: (i) the sustainability practices of the security's issuer or obligor, as applicable (each, an "issuer"), based on an evaluation of such issuer's individual ESG profile; (ii) information on a security's use of proceeds; and (iii) any third-party designation as a green, sustainable or sustainability-linked bond. A security's positive ESG characteristics can be determined under any of those three factors. Using the Adviser's proprietary ESG ratings process to evaluate the current state of an issuer's sustainability practices using a data-driven framework that includes both proprietary and third-party data, and also provide a qualitative forward-looking assessment of an issuer's sustainability outlook provided by the Adviser's fundamental research analysts and ESG team. The Adviser's ESG ratings of issuers are derived from multiple factors, including an issuer's environmental profile, which may include, but is not limited to, carbon and toxic emissions, water management, waste management, and vulnerability to the physical impacts of climate change. An assessment of an issuer's social profile includes, but is not limited to, its approach to quality health care access, housing affordability, human capital management, community reinvestment, and safety. An assessment of an issuer's governance profile includes, but is not limited to, its principles of management, oversight and transparency, governance efficiency and structure, and consideration of anticompetitive practices. These factors are weighted based on how material the Adviser believes each factor is to an issuer's financial outlook, effectiveness at service delivery, and long-term sustainability, and not all factors may be applicable to all issuers. Issuers with an above average ESG rating as determined by the Adviser are considered to have positive ESG characteristics and well-managed ESG risks. Assessing a security's use of proceeds by considering factors that provide ESG characteristics, such as energy efficiency, environmentally sustainable management, and providing access to quality health care, essential services and affordable housing. The Adviser will generally consider bonds that finance education, health care, affordable housing, clean energy, municipal water and sewer, public transportation, and designated green bonds, among others, as having positive ESG characteristics. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). In addition to focusing on municipal securities with positive ESG characteristics, the Adviser analyzes the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Normally maintaining a dollar-weighted average maturity between three and 10 years. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.                                
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 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 additional index has 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 institutional.fidelity.com for more recent performance information.                                
Performance Information Illustrates Variability of Returns [Text] 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] institutional.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 Narrative [Text Block] The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.                                
Bar Chart Does Not Reflect Sales Loads [Text] The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 7.08%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Sep. 30, 2023                                
Lowest Quarterly Return (2.85%)                                
Performance Table Heading Average Annual Returns                                
Performance Table Does Reflect Sales Loads Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges.                                
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 One Class of after Tax Shown [Text] After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary.                                
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 Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. 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. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. 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.                                
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | After Taxes on Distributions | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class A                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   0.94%                       2.32% [5]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | After Taxes on Distributions and Sales | Fidelity Advisor Sustainable Intermediate Municipal Income Fund - Class A                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   1.69%                       2.39% [5]      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                       2.79%      
FidelitySustainableIntermediateMunicipalIncomeFund-AMCIZPRO | Fidelity Sustainable Intermediate Municipal Income Fund | IXWQ5                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg 3-15 Year Blend (2-17) Municipal Bond Index                              
Average Annual Return, Percent   5.30%                       3.15%      
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund | Fidelity Sustainable Intermediate Municipal Income Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.43%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.78%                                
Expenses (as a percentage of Assets) 1.21%                                
Fee Waiver or Reimbursement [11] (0.84%)                                
Net Expenses (as a percentage of Assets) 0.37%                                
Expense Example, with Redemption, 1 Year $ 38                                
Expense Example, with Redemption, 3 Years 271                                
Expense Example, with Redemption, 5 Years 555                                
Expense Example, with Redemption, 10 Years $ 1,365                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   5.31%                       3.71% [12]      
Annual Return [Percent]     5.31% 1.37% 6.25%                        
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund /Class: Fidelity® Sustainable Intermediate Municipal Income Fund /Fidelity® Sustainable Intermediate Municipal Income Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® Sustainable Intermediate Municipal Income Fund seeks as high a level of current income, exempt from federal income tax, as is consistent with the preservation of capital.                                
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. 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 May 31, 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 16 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 16.00%                                
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 at least 80% of assets in municipal securities (i) whose interest is exempt from federal income tax and (ii) that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have positive environmental, social and governance (ESG) characteristics. The municipal securities in which the fund invests are normally investment-grade (those of medium and high quality). Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. 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. Evaluating each security in which the fund invests using both a traditional municipal bond credit, structure and relative value analysis and a consideration of the Adviser's judgment about the security's ESG characteristics. When assessing a security's ESG characteristics and its eligibility for purchase, the Adviser considers the following, where available: (i) the sustainability practices of the security's issuer or obligor, as applicable (each, an "issuer"), based on an evaluation of such issuer's individual ESG profile; (ii) information on a security's use of proceeds; and (iii) any third-party designation as a green, sustainable or sustainability-linked bond. A security's positive ESG characteristics can be determined under any of those three factors. Using the Adviser's proprietary ESG ratings process to evaluate the current state of an issuer's sustainability practices using a data-driven framework that includes both proprietary and third-party data, and also provide a qualitative forward-looking assessment of an issuer's sustainability outlook provided by the Adviser's fundamental research analysts and ESG team. The Adviser's ESG ratings of issuers are derived from multiple factors, including an issuer's environmental profile, which may include, but is not limited to, carbon and toxic emissions, water management, waste management, and vulnerability to the physical impacts of climate change. An assessment of an issuer's social profile includes, but is not limited to, its approach to quality health care access, housing affordability, human capital management, community reinvestment, and safety. An assessment of an issuer's governance profile includes, but is not limited to, its principles of management, oversight and transparency, governance efficiency and structure, and consideration of anticompetitive practices. These factors are weighted based on how material the Adviser believes each factor is to an issuer's financial outlook, effectiveness at service delivery, and long-term sustainability, and not all factors may be applicable to all issuers. Issuers with an above average ESG rating as determined by the Adviser are considered to have positive ESG characteristics and well-managed ESG risks. Assessing a security's use of proceeds by considering factors that provide ESG characteristics, such as energy efficiency, environmentally sustainable management, and providing access to quality health care, essential services and affordable housing. The Adviser will generally consider bonds that finance education, health care, affordable housing, clean energy, municipal water and sewer, public transportation, and designated green bonds, among others, as having positive ESG characteristics. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). In addition to focusing on municipal securities with positive ESG characteristics, the Adviser analyzes the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Normally maintaining a dollar-weighted average maturity between three and 10 years. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.                                
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 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 additional index has 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] 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] 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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 7.15%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Sep. 30, 2023                                
Lowest Quarterly Return (2.79%)                                
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 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. 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.                                
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund | After Taxes on Distributions | Fidelity Sustainable Intermediate Municipal Income Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   5.30%                       3.71% [12]      
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund | After Taxes on Distributions and Sales | Fidelity Sustainable Intermediate Municipal Income Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   4.43%                       3.53% [12]      
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                       2.79%      
FidelitySustainableIntermediateMunicipalIncomeFund-RetailPRO | Fidelity Sustainable Intermediate Municipal Income Fund | IXWQ5                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg 3-15 Year Blend (2-17) Municipal Bond Index                              
Average Annual Return, Percent   5.30%                       3.15%      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.20%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.40%                                
Expenses (as a percentage of Assets) 0.60%                                
Fee Waiver or Reimbursement [13] (0.40%)                                
Net Expenses (as a percentage of Assets) 0.20%                                
Expense Example, with Redemption, 1 Year $ 20                                
Expense Example, with Redemption, 3 Years 138                                
Expense Example, with Redemption, 5 Years 281                                
Expense Example, with Redemption, 10 Years $ 698                                
Annual Return, Inception Date Jun. 16, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   3.24%                       3.06% [14]      
Annual Return [Percent]     3.24% 3.32% 3.63%                        
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® SAI Sustainable Conservative Income Municipal Bond Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® SAI Sustainable Conservative Income Municipal Bond Fund seeks to provide a high level of income, exempt from federal income tax, consistent with preservation of capital.                                
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                                
Fee Waiver or Reimbursement over Assets, Date of Termination May 31, 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 70 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 70.00%                                
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 at least 80% of assets in U.S. dollar-denominated municipal money market securities and high quality investment-grade municipal debt securities (i) whose interest is exempt from federal income tax and (ii) that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have positive environmental, social and governance (ESG) characteristics. Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Municipal money market securities are high-quality, short-term debt securities that pay a fixed, variable, or floating interest rate, and include variable rate demand notes, commercial paper, and municipal notes. Municipal securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. High quality investment grade securities in which the fund invests include securities or issuers (i) rated at least A- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO) or similarly rated by the Adviser, and (ii) for securities with a credit maturity within one year, rated at least BBB or its equivalent by all NRSROs that rate the security and similarly rated by the Adviser. 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. Evaluating each security in which the fund invests using both a traditional municipal bond credit, structure and relative value analysis and a consideration of the Adviser's judgment about the security's ESG characteristics. When assessing a security's ESG characteristics and its eligibility for purchase, the Adviser considers the following, where available: (i) the sustainability practices of the security's issuer or obligor, as applicable (each, an "issuer"), based on an evaluation of such issuer's individual ESG profile; (ii) information on a security's use of proceeds; and (iii) any third-party designation as a green, sustainable or sustainability-linked bond. A security's positive ESG characteristics can be determined under any of those three factors. Using the Adviser's proprietary ESG ratings process to evaluate the current state of an issuer's sustainability practices using a data-driven framework that includes both proprietary and third-party data, and also provide a qualitative forward-looking assessment of an issuer's sustainability outlook provided by the Adviser's fundamental research analysts and ESG team. The Adviser's ESG ratings of issuers are derived from multiple factors, including an issuer's environmental profile, which may include, but is not limited to, carbon and toxic emissions, water management, waste management, and vulnerability to the physical impacts of climate change. An assessment of an issuer's social profile includes, but is not limited to, its approach to quality health care access, housing affordability, human capital management, community reinvestment, and safety. An assessment of an issuer's governance profile includes, but is not limited to, its principles of management, oversight and transparency, governance efficiency and structure, and consideration of anticompetitive practices. These factors are weighted based on how material the Adviser believes each factor is to an issuer's financial outlook, effectiveness at service delivery, and long-term sustainability, and not all factors may be applicable to all issuers. Issuers with an above average ESG rating as determined by the Adviser are considered to have positive ESG characteristics and well-managed ESG risks. Assessing a security's use of proceeds by considering factors that provide ESG characteristics, such as energy efficiency, environmentally sustainable management, and providing access to quality health care, essential services and affordable housing. The Adviser will generally consider bonds that finance education, health care, affordable housing, clean energy, municipal water and sewer, public transportation, and designated green bonds, among others, as having positive ESG characteristics. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). In addition to focusing on municipal securities with positive ESG characteristics, the Adviser analyzes the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Normally maintaining a dollar-weighted average maturity of one year or less. Normally investing in securities with a maximum maturity of four years. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.                                
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 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, 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.                                
Performance Information Illustrates Variability of Returns [Text] 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, a hypothetical composite of market indexes, and an additional index over various periods of time.                                
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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 1.60%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Sep. 30, 2023                                
Lowest Quarterly Return 0.53%                                
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 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. 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.                                
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | After Taxes on Distributions | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   3.23%                       3.05% [14]      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | After Taxes on Distributions and Sales | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   3.15%                       3.04% [14]      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                       3.78%      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | IXV4E                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Fidelity Conservative Income Municipal Bond Composite Index℠                              
Average Annual Return, Percent   3.16%                       2.92%      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Conservative Income Municipal Bond Fund | LB319                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond 1 Year (1-2 Y) Index                              
Average Annual Return, Percent   3.47%                       2.80%      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund | Fidelity SAI Sustainable Municipal Income Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.33%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.20%                                
Expenses (as a percentage of Assets) 0.53%                                
Fee Waiver or Reimbursement [15] (0.17%)                                
Net Expenses (as a percentage of Assets) 0.36%                                
Expense Example, with Redemption, 1 Year $ 37                                
Expense Example, with Redemption, 3 Years 147                                
Expense Example, with Redemption, 5 Years 273                                
Expense Example, with Redemption, 10 Years $ 643                                
Annual Return, Inception Date Apr. 13, 2022                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   4.66%                       3.74% [16]      
Annual Return [Percent]     4.66% 1.02% 8.04%                        
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® SAI Sustainable Municipal Income Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® SAI Sustainable Municipal Income Fund seeks to provide a high current yield exempt from federal income tax.                                
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                                
Fee Waiver or Reimbursement over Assets, Date of Termination May 31, 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 10 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 10.00%                                
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 at least 80% of assets in municipal securities (i) whose interest is exempt from federal income tax and (ii) that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have positive environmental, social and governance (ESG) characteristics. The municipal securities in which the fund invests are normally investment-grade (those of medium and high quality). Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. 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. Evaluating each security in which the fund invests using both a traditional municipal bond credit, structure and relative value analysis and a consideration of the Adviser's judgment about the security's ESG characteristics. When assessing a security's ESG characteristics and its eligibility for purchase, the Adviser considers the following, where available: (i) the sustainability practices of the security's issuer or obligor, as applicable (each, an "issuer"), based on an evaluation of such issuer's individual ESG profile; (ii) information on a security's use of proceeds; and (iii) any third-party designation as a green, sustainable or sustainability-linked bond. A security's positive ESG characteristics can be determined under any of those three factors. Using the Adviser's proprietary ESG ratings process to evaluate the current state of an issuer's sustainability practices using a data-driven framework that includes both proprietary and third-party data, and also provide a qualitative forward-looking assessment of an issuer's sustainability outlook provided by the Adviser's fundamental research analysts and ESG team. The Adviser's ESG ratings of issuers are derived from multiple factors, including an issuer's environmental profile, which may include, but is not limited to, carbon and toxic emissions, water management, waste management, and vulnerability to the physical impacts of climate change. An assessment of an issuer's social profile includes, but is not limited to, its approach to quality health care access, housing affordability, human capital management, community reinvestment, and safety. An assessment of an issuer's governance profile includes, but is not limited to, its principles of management, oversight and transparency, governance efficiency and structure, and consideration of anticompetitive practices. These factors are weighted based on how material the Adviser believes each factor is to an issuer's financial outlook, effectiveness at service delivery, and long-term sustainability, and not all factors may be applicable to all issuers. Issuers with an above average ESG rating as determined by the Adviser are considered to have positive ESG characteristics and well-managed ESG risks. Assessing a security's use of proceeds by considering factors that provide ESG characteristics, such as energy efficiency, environmentally sustainable management, and providing access to quality health care, essential services and affordable housing. The Adviser will generally consider bonds that finance education, health care, affordable housing, clean energy, municipal water and sewer, public transportation, and designated green bonds, among others, as having positive ESG characteristics. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). In addition to focusing on municipal securities with positive ESG characteristics, the Adviser analyzes the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Employing sustainable investing exclusion criteria to avoid investments in issuers that are directly engaged in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.                                
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 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 additional index has 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] 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] 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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 9.37%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Sep. 30, 2023                                
Lowest Quarterly Return (3.76%)                                
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 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. 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.                                
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund | After Taxes on Distributions | Fidelity SAI Sustainable Municipal Income Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   4.66%                       3.73% [16]      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund | After Taxes on Distributions and Sales | Fidelity SAI Sustainable Municipal Income Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   4.11%                       3.59% [16]      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                       2.79%      
FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO | Fidelity SAI Sustainable Municipal Income Fund | LB083                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg 3+ Year Municipal Bond Index                              
Average Annual Return, Percent   4.30%                       2.79%      
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund | Fidelity Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.42%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.01%                                
Expenses (as a percentage of Assets) 0.43%                                
Fee Waiver or Reimbursement [17] (0.18%)                                
Net Expenses (as a percentage of Assets) 0.25%                                
Expense Example, with Redemption, 1 Year $ 26                                
Expense Example, with Redemption, 3 Years 113                                
Expense Example, with Redemption, 5 Years 217                                
Expense Example, with Redemption, 10 Years $ 519                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   4.49%                         1.07%   2.62%
Annual Return [Percent]     4.49% 1.77% 7.50% (10.12%) 2.62% 5.01% 8.57% 0.86% 6.43% 0.37%          
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® Tax-Free Bond Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® Tax-Free Bond Fund seeks to provide a high current yield exempt from federal income tax.                                
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. You may pay other fees, such as brokerage commissions, 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 May 31, 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 20 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 20.00%                                
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 at least 80% of assets in municipal securities whose interest is exempt from federal income tax. The municipal securities in which the fund invests are normally investment-grade (those of medium and high quality). Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. 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 not investing in municipal securities whose interest is subject to federal income tax or in municipal securities whose interest is subject to the federal alternative minimum tax. Managing the fund to have similar overall interest rate risk to the index. Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities 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 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 additional index has 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] 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] 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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 8.20%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Mar. 31, 2022                                
Lowest Quarterly Return (6.57%)                                
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 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. 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.                                
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund | After Taxes on Distributions | Fidelity Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   4.49%                         1.05%   2.57%
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund | After Taxes on Distributions and Sales | Fidelity Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   3.98%                         1.46%   2.69%
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund | LB123                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg 3+ Year Non-AMT Municipal Bond Index                              
Average Annual Return, Percent   4.27%                         0.66%   2.43%
FidelityTax-FreeBondFund-PRO | Fidelity Tax-Free Bond Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                         0.80%   2.34%
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund | Fidelity SAI Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Management Fees (as a percentage of Assets) 0.33%                                
Distribution and Service (12b-1) Fees 0.00%                                
Other Expenses (as a percentage of Assets): 0.02%                                
Expenses (as a percentage of Assets) 0.35%                                
Fee Waiver or Reimbursement [18] (0.10%)                                
Net Expenses (as a percentage of Assets) 0.25%                                
Expense Example, with Redemption, 1 Year $ 26                                
Expense Example, with Redemption, 3 Years 99                                
Expense Example, with Redemption, 5 Years 183                                
Expense Example, with Redemption, 10 Years $ 430                                
Annual Return, Inception Date Oct. 02, 2018                                
Average Annual Return, Label [Optional Text]   Return Before Taxes                              
Average Annual Return, Percent   4.15%                         1.14% 2.70% [19]  
Annual Return [Percent]     4.15% 1.77% 7.65% (9.32%) 2.28% 3.90% 8.25%                
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Risk/Return [Heading] Fund Summary Fund: Fidelity® SAI Tax-Free Bond Fund                                
Objective [Heading] Investment Objective                                
Objective, Primary [Text Block] Fidelity® SAI Tax-Free Bond Fund seeks to provide a high current yield exempt from federal income tax.                                
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                                
Fee Waiver or Reimbursement over Assets, Date of Termination May 31, 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 12 % of the average value of its portfolio.                                
Portfolio Turnover, Rate 12.00%                                
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 at least 80% of assets in municipal securities whose interest is exempt from federal income tax. The municipal securities in which the fund invests are normally investment-grade (those of medium and high quality). Municipal debt securities are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, financing for eligible non-profit organizations, or financing for a specific project or public facility. Municipal debt securities in which the fund invests include securities issued by U.S. territories and possessions, general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, or pre-refunded or escrowed bonds, municipal money market securities, and synthetic securities. Municipal securities usually pay a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. 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 not investing in municipal securities whose interest is subject to federal income tax or in municipal securities whose interest is subject to the federal alternative minimum tax. Managing the fund to have similar overall interest rate risk to the supplemental index (see "Additional Index Information" section of the prospectus). Allocating assets across different market sectors and maturities. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities 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 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 additional index has 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] 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] 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                                
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                                
Highest Quarterly Return, Date Dec. 31, 2023                                
Highest Quarterly Return 8.35%                                
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                                
Lowest Quarterly Return, Date Mar. 31, 2022                                
Lowest Quarterly Return (6.61%)                                
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 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. 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.                                
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund | After Taxes on Distributions | Fidelity SAI Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                              
Average Annual Return, Percent   4.14%                         1.14% 2.69% [19]  
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund | After Taxes on Distributions and Sales | Fidelity SAI Tax-Free Bond Fund                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                              
Average Annual Return, Percent   3.80%                         1.46% 2.66% [19]  
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund | LB123                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg 3+ Year Non-AMT Municipal Bond Index                              
Average Annual Return, Percent   4.27%                         0.66% 2.58%  
FidelitySAITax-FreeBondFund-PRO | Fidelity SAI Tax-Free Bond Fund | LB015                                  
Prospectus Line Items                                  
Average Annual Return, Label [Optional Text]   Bloomberg Municipal Bond Index                              
Average Annual Return, Percent   4.25%                         0.80% 2.51%  
Document Type 485BPOS                                
Registrant Name Fidelity Salem Street Trust                                
[1]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.20% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[2]
A From November 6, 2023 .
[3]
A Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 0.75% and 0.25%, respectively.
[4]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse Class A, Class M, Class C, Class I, and Class Z of the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of their respective average net assets, exceed 0.62%, 0.62%, 1.37%, 0.37%, and 0.31% (the Expense Caps). If at any time during the current fiscal year expenses for Class A, Class M, Class C, Class I, or Class Z of the fund fall below the Expense Caps, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Caps. These arrangements will remain in effect through May 31, 2027 . FMR may not terminate these arrangements before the expiration date without the approval of the Board of Trustees and may extend them in its discretion after that date.
[5]
A From April 13, 2022 .
[6]
B From April 13, 2022 .
[7]
B On Class C shares redeemed less than one year after purchase.
[8]
C From April 13, 2022 .
[9]
D From April 13, 2022 .
[10]
E From April 13, 2022 .
[11]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the class of shares of the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.37% (the Expense Cap). If at any time during the current fiscal year expenses for the class of shares of the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[12]
A From April 13, 2022 .
[13]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.20% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[14]
A From June 16, 2022 .
[15]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.36% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[16]
A From April 13, 2022 .
[17]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.25% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[18]
A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.25% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through May 31, 2027 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.
[19]
A From October 2, 2018 .