Risk/Return Summary - FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO - FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO - Fidelity SAI Sustainable Municipal Income Fund	Apr. 01, 2025
Risk Lose Money [Text]
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Risk Text Block	You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text]
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Risk Text Block	An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency .
IssuerSpecificChangesMember
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Risk Text Block	Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support (such as guarantees) or a maturity-shortening structure (such as demand and put features) for a security can cause the price of a security to decrease.
ManagementRiskMember
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Risk Text Block	Management Risk. The Adviser's application of the fund's strategy criteria may not achieve its intended results. The fund could underperform in comparison to other funds with a similar benchmark or similar objectives and investment strategies .
InterestRateChangesMember
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Risk Text Block	Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
SustainabilityRiskMember
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Risk Text Block	Sustainability Risk. Application of Fidelity Management & Research Company LLC's (FMR) (the Adviser) ESG ratings process and/or its sustainable investing exclusion criteria may affect the fund's exposure to certain issuers, sectors, regions, and countries and may affect the fund's performance depending on whether certain investments are in or out of favor. The criteria related to the fund's ESG ratings process and/or adherence to its sustainable investing exclusion criteria may result in the fund forgoing opportunities to buy certain securities when it might otherwise be advantageous to do so, or selling securities for ESG reasons when it might be otherwise disadvantageous for it to do so. As a result, the fund's performance may at times be better or worse than the performance of funds that do not use ESG or sustainability criteria. There are significant differences in interpretations of what it means for an issuer to have positive ESG factors. While the Adviser believes its definitions are reasonable, the portfolio decisions it makes may differ with other investors' or advisers' views. When evaluating an issuer, the Adviser is dependent on information or data obtained through voluntary or third-party reporting that may be incomplete, inaccurate, or unavailable, which could cause the Adviser to incorrectly assess an issuer's business practices.
MunicipalMarketVolatilityMember
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Risk Text Block	Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.

Risk/Return Summary - FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO - FidelitySAISustainableMunicipalIncomeSustainableConservativeIncomeMunicipalBondFunds-ComboPRO - Fidelity SAI Sustainable Municipal Income Fund

Apr. 01, 2025

You could lose money by investing in the fund.

Risk Not Insured Depository Institution [Text]

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Risk Text Block

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency .

IssuerSpecificChangesMember

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Risk Text Block

Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support (such as guarantees) or a maturity-shortening structure (such as demand and put features) for a security can cause the price of a security to decrease.

ManagementRiskMember

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Risk Text Block

Management Risk. The Adviser's application of the fund's strategy criteria may not achieve its intended results. The fund could underperform in comparison to other funds with a similar benchmark or similar objectives and investment strategies .

InterestRateChangesMember

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Risk Text Block

Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.

SustainabilityRiskMember

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Risk Text Block

Sustainability Risk. Application of Fidelity Management & Research Company LLC's (FMR) (the Adviser) ESG ratings process and/or its sustainable investing exclusion criteria may affect the fund's exposure to certain issuers, sectors, regions, and countries and may affect the fund's performance depending on whether certain investments are in or out of favor. The criteria related to the fund's ESG ratings process and/or adherence to its sustainable investing exclusion criteria may result in the fund forgoing opportunities to buy certain securities when it might otherwise be advantageous to do so, or selling securities for ESG reasons when it might be otherwise disadvantageous for it to do so. As a result, the fund's performance may at times be better or worse than the performance of funds that do not use ESG or sustainability criteria. There are significant differences in interpretations of what it means for an issuer to have positive ESG factors. While the Adviser believes its definitions are reasonable, the portfolio decisions it makes may differ with other investors' or advisers' views. When evaluating an issuer, the Adviser is dependent on information or data obtained through voluntary or third-party reporting that may be incomplete, inaccurate, or unavailable, which could cause the Adviser to incorrectly assess an issuer's business practices.

MunicipalMarketVolatilityMember

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Risk Text Block

Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities.