Risk/Return Summary - FidelitySeriesInternationalDevelopedMarketsBondIndexFund-PRO - FidelitySeriesInternationalDevelopedMarketsBondIndexFund-PRO - Fidelity Series International Developed Markets Bond Index Fund	Mar. 01, 2025
Risk Nondiversified Status [Text]
Prospectus Line Items
Risk Text Block	In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.
Risk Lose Money [Text]
Prospectus Line Items
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 .
LeverageRiskMember
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Risk Text Block	Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
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.
CorrelationToIndexMember
Prospectus Line Items
Risk Text Block	Correlation to Index. The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund, transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.
InterestRateChangesMember
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Risk Text Block	Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
ForeignCurrencyTransactionsMember
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Risk Text Block	Foreign Currency Transactions. Although a forward foreign currency exchange contract is used to reduce or hedge a fund's exposure to changes in the value of the currency, suitable hedging transactions may not be available in all circumstances, may not be successful, and may eliminate any chance for the fund to benefit from favorable fluctuations in relevant foreign currencies.
ForeignExposureMember
Prospectus Line Items
Risk Text Block	Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. Foreign exchange rates also can be extremely volatile.
PassiveManagementRiskMember
Prospectus Line Items
Risk Text Block	Passive Management Risk. The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the fund's index or of the actual securities included in the index. This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund's performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities or lessen the impact of a market decline or a decline in the value of one or more issuers. The fund will be concentrated to approximately the same extent that the fund's index concentrates in the securities of issuers in a particular industry.
PrepaymentMember
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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.
GeographicExposureToEuropeMember
Prospectus Line Items
Risk Text Block	Geographic Exposure to Europe. Because the fund invests a meaningful portion of its assets in Europe, the fund's performance is expected to be closely tied to social, political, and economic conditions within Europe and to be more volatile than the performance of more geographically diversified funds.

Risk/Return Summary - FidelitySeriesInternationalDevelopedMarketsBondIndexFund-PRO - FidelitySeriesInternationalDevelopedMarketsBondIndexFund-PRO - Fidelity Series International Developed Markets Bond Index Fund

Mar. 01, 2025

In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

Prospectus Line Items

Risk Text Block

You could lose money by investing in the fund.

Risk Not Insured Depository Institution [Text]

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 .

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.

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. 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.

CorrelationToIndexMember

Prospectus Line Items

Risk Text Block

Correlation to Index. The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund, transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.

InterestRateChangesMember

Prospectus Line Items

Risk Text Block

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

ForeignCurrencyTransactionsMember

Prospectus Line Items

Risk Text Block

Foreign Currency Transactions. Although a forward foreign currency exchange contract is used to reduce or hedge a fund's exposure to changes in the value of the currency, suitable hedging transactions may not be available in all circumstances, may not be successful, and may eliminate any chance for the fund to benefit from favorable fluctuations in relevant foreign currencies.

ForeignExposureMember

Prospectus Line Items

Risk Text Block

Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. Foreign exchange rates also can be extremely volatile.

PassiveManagementRiskMember

Prospectus Line Items

Risk Text Block

Passive Management Risk. The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the fund's index or of the actual securities included in the index. This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund's performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities or lessen the impact of a market decline or a decline in the value of one or more issuers. The fund will be concentrated to approximately the same extent that the fund's index concentrates in the securities of issuers in a particular industry.

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.

GeographicExposureToEuropeMember

Prospectus Line Items

Risk Text Block

Geographic Exposure to Europe. Because the fund invests a meaningful portion of its assets in Europe, the fund's performance is expected to be closely tied to social, political, and economic conditions within Europe and to be more volatile than the performance of more geographically diversified funds.