v3.26.1
Investment Risks
Apr. 29, 2026
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index 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 .
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | 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.
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | RulesBasedStrategyRiskMember  
Prospectus Line Items  
Risk [Text Block] Rules-Based Strategy Risk. Although the index uses a rules-based proprietary index methodology, there is no guarantee that this methodology will be successful. 
FidelityFlex500IndexFund-PRO | Fidelity Flex 500 Index Fund | 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.
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | Risk Nondiversified Status [Member]  
Prospectus Line Items  
Risk [Text Block] In addition, the fund may operate as a non-diversified fund under the 1940 Act to the approximate extent the index is non-diversified. A non-diversified fund may invest a greater portion of its 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.
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
Fidelity500IndexFund-PRO | Fidelity 500 Index 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 .
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
Fidelity500IndexFund-PRO | Fidelity 500 Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | 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.
Fidelity500IndexFund-PRO | Fidelity 500 Index Fund | 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.
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index 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 .
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | 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 .
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | RulesBasedStrategyRiskMember  
Prospectus Line Items  
Risk [Text Block] Rules-Based Strategy Risk. Although the index uses a rules-based proprietary index methodology, there is no guarantee that this methodology will be successful. 
FidelityFlexLargeCapFocusedIndexFund-Pro | Fidelity Flex Large Cap Focused Index Fund | 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.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | Risk Nondiversified Status [Member]  
Prospectus Line Items  
Risk [Text Block] In addition, the fund may operate as a non-diversified fund under the 1940 Act to the approximate extent the index is non-diversified. A non-diversified fund may invest a greater portion of its 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.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index 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 .
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | 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.
FidelitySeriesTotalMarketIndexFund-PRO | Fidelity Series Total Market Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index 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 .
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | MidCapInvestingMember  
Prospectus Line Items  
Risk [Text Block] Mid Cap Investing. The value of securities of medium size, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | SmallCapInvestingMember  
Prospectus Line Items  
Risk [Text Block] Small Cap Investing. The value of securities of smaller, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Extended Market Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index 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 .
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | GeographicExposureToJapanMember  
Prospectus Line Items  
Risk [Text Block] Geographic Exposure to Japan. Because the fund invests a meaningful portion of its assets in Japan, the fund's performance is expected to be closely tied to social, political, and economic conditions within Japan and to be more volatile than the performance of more geographically diversified funds.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity International Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | Risk Nondiversified Status [Member]  
Prospectus Line Items  
Risk [Text Block] In addition, the fund may operate as a non-diversified fund under the 1940 Act to the approximate extent the index is non-diversified. A non-diversified fund may invest a greater portion of its 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | Risk Lose Money [Member]  
Prospectus Line Items  
Risk [Text Block]   You could lose money by investing in the fund.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index 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 .
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | SecuritiesLendingRiskMember  
Prospectus Line Items  
Risk [Text Block] Securities Lending Risk. Securities lending involves the risk that the borrower may fail to return the securities loaned in a timely manner or at all. If the borrower defaults on its obligation to return the securities loaned because of insolvency or other reasons, a fund could experience delays and costs in recovering the securities loaned or in gaining access to the collateral.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index 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. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | StockMarketVolatilityMember  
Prospectus Line Items  
Risk [Text Block] Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | 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.
FidelityExtendedMarketInternationalandTotalMarketIndexFunds-ComboPRO | Fidelity Total Market Index Fund | 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.
Document Type 485BPOS