3.21.2 html 5 157 1 true 5 0 false 2 false false R1.htm 000000 - Document - Document and Entity Information {Elements} Sheet http://www.proofPlus.com/role/DocumentInformation Document and Entity Information 1 false false R2.htm 000001 - Document - Risk/Return Summary {Unlabeled} - Fidelity Government Money Market Fund Sheet http://www.proofPlus.com/role/SummaryS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Risk/Return Summary- Fidelity Government Money Market Fund 2 false false R3.htm 000002 - Schedule - Shareholder Fees {- Fidelity Government Money Market Fund} Sheet http://www.proofPlus.com/role/ShareholderFeesS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Shareholder Fees {- Fidelity Government Money Market Fund} 3 false false R4.htm 000003 - Schedule - Annual Operating Expenses {- Fidelity Government Money Market Fund} Sheet http://www.proofPlus.com/role/OperatingExpensesS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Annual Operating Expenses {- Fidelity Government Money Market Fund} 4 false false R5.htm 000004 - Schedule - Expense Example {- Fidelity Government Money Market Fund} Sheet http://www.proofPlus.com/role/ExpenseExampleS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Expense Example {- Fidelity Government Money Market Fund} 5 false false R6.htm 000006 - Schedule - Annual Total Returns - Fidelity Government Money Market Fund [BarChart] Sheet http://www.proofPlus.com/role/AnnualTotalReturnsBarChartS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Annual Total Returns - Fidelity Government Money Market Fund [BarChart] 6 false false R7.htm 000007 - Schedule - Average Annual Total Returns {Transposed} {- Fidelity Government Money Market Fund} Sheet http://www.proofPlus.com/role/AverageAnnualTotalReturnsS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Average Annual Total Returns{- Fidelity Government Money Market Fund} 7 false false R8.htm 000009 - Disclosure - Risk/Return Detail Data {Elements} - Fidelity Government Money Market Fund Sheet http://www.proofPlus.com/role/DisclosureDetailS000007051_NF0430FidelityGovernmentMoneyMarketFundClassSPro01 Risk/Return Detail Data- Fidelity Government Money Market Fund 8 false false R9.htm 040000 - Disclosure - Risk/Return Detail Data {Elements} Sheet http://xbrl.sec.gov/rr/role/RiskReturnDetailData Risk/Return Detail Data 9 false false All Reports Book All Reports filing912.htm exi.htm exj.htm exm8.htm exn1.htm exn2.htm qsk-20211126.xsd qsk-20211126_cal.xml qsk-20211126_def.xml qsk-20211126_lab.xml qsk-20211126_pre.xml fi_logo.jpg fipro_logo.jpg img747274712.jpg http://xbrl.sec.gov/dei/2020-01-31 http://xbrl.sec.gov/rr/2018-01-31 true true