| Label | Element | Value |
|---|---|---|
| FIMMFunds-SelectComboPRO | ForeignExposureMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. |
| FIMMFunds-SelectComboPRO | ForeignExposureMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries . |
| FIMMFunds-SelectComboPRO | MunicipalMarketVolatilityMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | 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. |
| FIMMFunds-SelectComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-SelectComboPRO | IncomeRiskMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-SelectComboPRO | IncomeRiskMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-SelectComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-SelectComboPRO | IncomeRiskMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-SelectComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | FinancialServicesConcentrationMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Financial Services Concentration. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. |
| FIMMFunds-SelectComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-SelectComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. |
| FIMMFunds-Class2ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries . |
| FIMMFunds-Class2ComboPRO | MunicipalMarketVolatilityMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | 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. |
| FIMMFunds-Class2ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class2ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class2ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class2ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class2ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class2ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | FinancialServicesConcentrationMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Financial Services Concentration. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. |
| FIMMFunds-Class2ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class2ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. |
| FIMMFunds-Class1ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries . |
| FIMMFunds-Class1ComboPRO | MunicipalMarketVolatilityMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | 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. |
| FIMMFunds-Class1ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class1ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class1ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class1ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class1ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class1ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | FinancialServicesConcentrationMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Financial Services Concentration. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. |
| FIMMFunds-Class1ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class1ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. |
| FIMMFunds-Class3ComboPRO | ForeignExposureMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries . |
| FIMMFunds-Class3ComboPRO | MunicipalMarketVolatilityMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | 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. |
| FIMMFunds-Class3ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class3ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class3ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class3ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class3ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class3ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | FinancialServicesConcentrationMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Financial Services Concentration. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. |
| FIMMFunds-Class3ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class3ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Tax-Exempt Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class4ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class4ComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-Class4ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class4ComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-Class4ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-Class4ComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | ForeignExposureMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Foreign Exposure. Entities located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. |
| FIMMFunds-InstitutionalComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-InstitutionalComboPRO | IncomeRiskMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-InstitutionalComboPRO | IncomeRiskMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-InstitutionalComboPRO | IncomeRiskMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Income Risk. A low or negative interest rate environment can adversely affect the fund's yield. |
| FIMMFunds-InstitutionalComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | IssuerSpecificChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | FinancialServicesConcentrationMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Financial Services Concentration. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. |
| FIMMFunds-InstitutionalComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Government Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Money Market Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |
| FIMMFunds-InstitutionalComboPRO | InterestRateChangesMember | Fidelity Investments Money Market Treasury Only Portfolio | ||
| Risk Text Block | rr_RiskTextBlock | Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. |