Investment Risks	Sep. 29, 2026
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| Risk Lose Money [Member]
Prospectus Line Items
Risk [Text Block]	You could lose money by investing in the fund.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| Risk Not Insured Depository Institution [Member]
Prospectus Line Items
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 .
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| InterestRateChangesMember
Prospectus Line Items
Risk [Text Block]	Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| LeverageRiskMember
Prospectus Line Items
Risk [Text Block]	Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| HighPortfolioTurnoverMember
Prospectus Line Items
Risk [Text Block]	High Portfolio Turnover. High portfolio turnover (more than 100%) may result in increased transaction costs and potentially higher capital gains or losses. The effects of higher than normal portfolio turnover may adversely affect the fund's performance.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| IssuerSpecificChangesMember
Prospectus Line Items
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.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| PrepaymentMember
Prospectus Line Items
Risk [Text Block]	Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
FidelityGNMAFund-PRO \| Fidelity GNMA Fund \| USGovernmentObligationsRiskMember
Prospectus Line Items
Risk [Text Block]	U.S. Government Obligations Risk. Certain securities in which the fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States.
Document Type	485BPOS

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 .

Risk [Text Block]

Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.

Prospectus Line Items

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.

Prospectus Line Items

Risk [Text Block]

U.S. Government Obligations Risk. Certain securities in which the fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States.