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    <dei:EntityRegistrantName contextRef="Trust" id="ixv-61163">Fidelity Hereford Street Trust</dei:EntityRegistrantName>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-102">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:MaterialFundChngNoticeTextBlock contextRef="C000019232_ClassMember" id="ixv-106">This report describes changes to the Fund that occurred during the reporting period.</oef:MaterialFundChngNoticeTextBlock>
    <oef:FundName contextRef="C000019232_ClassMember" id="ixv-117">Fidelity&#xae; Treasury Only Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000019232_ClassMember" id="ixv-120">Fidelity&#xae; Treasury Only Money Market Fund</oef:ClassName>
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    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000019232_ClassMember" id="ixv-143">This annual shareholder report contains information about Fidelity&#xae; Treasury Only Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000019232_ClassMember" id="ixv-145">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000019232_ClassMember" id="ixv-150">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
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    <oef:ExpensesTextBlock contextRef="C000019232_ClassMember" id="ixv-165">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Treasury Only Money Market Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;43&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.42&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
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    <oef:AddlFundStatisticsTextBlock contextRef="C000019232_ClassMember" id="ixv-213">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
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&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
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&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
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&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;16,940,567,988&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;57&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;61,283,591&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
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&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
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&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

19.9

&#160;


8-30

17.9

&#160;


31-60

24.1

&#160;


61-90

21.0

&#160;


91-180

16.4

&#160;


&gt;180

1.6

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
U.S. Treasury Obligations

100.9




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

U.S. Treasury Obligations - 100.9&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (0.9)%


&#160;






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&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;How has the Fund changed?&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-8544&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:50%; background-color:#ebf3e9;border-right:2px dashed #368627;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:50%; background-color:#ebf3e9;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngTextBlock>
    <oef:SummaryOfChngLegendTextBlock contextRef="C000019232_ClassMember" id="ixv-417">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-8544&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;</oef:SummaryOfChngLegendTextBlock>
    <oef:UpdProspectusWebAddress contextRef="C000019232_ClassMember" id="ixv-421">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;</oef:UpdProspectusWebAddress>
    <oef:UpdProspectusPhoneNumber contextRef="C000019232_ClassMember" id="ixv-424">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-8544&lt;/span&gt;</oef:UpdProspectusPhoneNumber>
    <oef:UpdProspectusEmailAddress contextRef="C000019232_ClassMember" id="ixv-428">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;</oef:UpdProspectusEmailAddress>
    <oef:MaterialFundChngStrategiesTextBlock contextRef="C000019232_ClassMember" id="ixv-439">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngStrategiesTextBlock>
    <oef:MaterialFundChngRisksChngTextBlock contextRef="C000019232_ClassMember" id="ixv-446">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;</oef:MaterialFundChngRisksChngTextBlock>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-502">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000203454_ClassMember" id="ixv-514">Fidelity&#xae; Series Treasury Bill Index Fund</oef:FundName>
    <oef:ClassName contextRef="C000203454_ClassMember" id="ixv-517">Fidelity&#xae; Series Treasury Bill Index Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000203454_ClassMember" id="ixv-521">FHQFX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000203454_ClassMember" id="ixv-540">This annual shareholder report contains information about Fidelity&#xae; Series Treasury Bill Index Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000203454_ClassMember" id="ixv-542">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000203454_ClassMember" id="ixv-547">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000203454_ClassMember" id="ixv-549">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000203454_ClassMember" id="ixv-552">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:ExpensesTextBlock contextRef="C000203454_ClassMember" id="ixv-559">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Series Treasury Bill Index Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;0&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.00&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;B&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans Cd';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Amount represents less than $.50&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;B &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans Cd';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Amount represents less than 0.005%&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000203454_ClassMember"
      decimals="0"
      id="ixv-62720"
      unitRef="usd">0</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000203454_ClassMember"
      decimals="INF"
      id="ixv-62721"
      unitRef="pure">0.0000</oef:ExpenseRatioPct>
    <oef:FactorsAffectingPerfTextBlock contextRef="C000203454_ClassMember" id="ixv-611">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What affected the Fund's performance this period?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;text-indent:-24px;margin-bottom:2px;margin-left:24px;margin-top:5px;margin-right:0px;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#x2022;&lt;span style="padding-right:10px"&gt;&lt;/span&gt;U.S. taxable investment-grade bonds achieved a solid gain for the 12 months ending April 30, 2026, navigating uncertainty related to U.S. trade policy and geopolitical events but buoyed by attractive starting yields, a resilient economy and three policy interest-rate cuts by the Federal Reserve in the second half of 2025.&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;text-indent:-24px;margin-bottom:2px;margin-left:24px;margin-top:5px;margin-right:0px;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#x2022;&lt;span style="padding-right:10px"&gt;&lt;/span&gt;We construct the portfolio using optimization. This approach minimizes the differences between risk exposures of the fund relative to the index. We attempt to hold all positions held by the index in the same relative proportions.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;text-indent:-24px;margin-bottom:2px;margin-left:24px;margin-top:5px;margin-right:0px;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#x2022;&lt;span style="padding-right:10px"&gt;&lt;/span&gt;Exposures include duration, key-rate durations and other factors.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:FactorsAffectingPerfTextBlock>
    <oef:LineGraphTableTextBlock contextRef="C000203454_ClassMember" id="ixv-626">How did the Fund perform over the life of Fund?

 &#160;&#160;
CUMULATIVE PERFORMANCE
August 17, 2018 through April 30, 2026. 
Initial investment of $10,000.
Fidelity&#xae; Series Treasury Bill Index Fund


$10,000

$10,162


$10,400


$10,413


$10,418


$10,707


$11,280


$11,854


$12,331



Bloomberg U.S. 3-6 Month Treasury Bill Index


$10,000

$10,167


$10,407


$10,421


$10,422


$10,715


$11,290


$11,857


$12,342



Bloomberg U.S. Aggregate Bond Index


$10,000

$10,413


$11,542


$11,511


$10,531


$10,486


$10,332


$11,161


$11,613



&#160;

2018

2019

2020

2021

2022

2023

2024

2025

2026









&#160;
</oef:LineGraphTableTextBlock>
    <oef:LineGraphAndTableMeasureName contextRef="C000203454_LG_ClassMember_9YR" id="ixv-645">&lt;span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Series Treasury Bill Index Fund&lt;/span&gt;</oef:LineGraphAndTableMeasureName>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2018"
      decimals="0"
      id="ixv-62722"
      unitRef="usd">10000</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2019"
      decimals="0"
      id="ixv-62723"
      unitRef="usd">10162</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2020"
      decimals="0"
      id="ixv-62724"
      unitRef="usd">10400</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2021"
      decimals="0"
      id="ixv-62725"
      unitRef="usd">10413</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2022"
      decimals="0"
      id="ixv-62726"
      unitRef="usd">10418</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2023"
      decimals="0"
      id="ixv-62727"
      unitRef="usd">10707</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2024"
      decimals="0"
      id="ixv-62728"
      unitRef="usd">11280</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2025"
      decimals="0"
      id="ixv-62729"
      unitRef="usd">11854</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_ClassMember_AsOf_2026"
      decimals="0"
      id="ixv-62730"
      unitRef="usd">12331</oef:AccmVal>
    <oef:LineGraphAndTableMeasureName
      contextRef="C000203454_LG_1_AdditionalIndexMember_9YR"
      id="ixv-686">&lt;span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;"&gt;Bloomberg U.S. 3-6 Month Treasury Bill Index&lt;/span&gt;</oef:LineGraphAndTableMeasureName>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2018"
      decimals="0"
      id="ixv-62731"
      unitRef="usd">10000</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2019"
      decimals="0"
      id="ixv-62732"
      unitRef="usd">10167</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2020"
      decimals="0"
      id="ixv-62733"
      unitRef="usd">10407</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2021"
      decimals="0"
      id="ixv-62734"
      unitRef="usd">10421</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2022"
      decimals="0"
      id="ixv-62735"
      unitRef="usd">10422</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2023"
      decimals="0"
      id="ixv-62736"
      unitRef="usd">10715</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2024"
      decimals="0"
      id="ixv-62737"
      unitRef="usd">11290</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2025"
      decimals="0"
      id="ixv-62738"
      unitRef="usd">11857</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_1_AdditionalIndexMember_AsOf_2026"
      decimals="0"
      id="ixv-62739"
      unitRef="usd">12342</oef:AccmVal>
    <oef:LineGraphAndTableMeasureName
      contextRef="C000203454_LG_2_AdditionalIndexMember_9YR"
      id="ixv-727">&lt;span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;"&gt;Bloomberg U.S. Aggregate Bond Index&lt;/span&gt;</oef:LineGraphAndTableMeasureName>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2018"
      decimals="0"
      id="ixv-62740"
      unitRef="usd">10000</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2019"
      decimals="0"
      id="ixv-62741"
      unitRef="usd">10413</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2020"
      decimals="0"
      id="ixv-62742"
      unitRef="usd">11542</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2021"
      decimals="0"
      id="ixv-62743"
      unitRef="usd">11511</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2022"
      decimals="0"
      id="ixv-62744"
      unitRef="usd">10531</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2023"
      decimals="0"
      id="ixv-62745"
      unitRef="usd">10486</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2024"
      decimals="0"
      id="ixv-62746"
      unitRef="usd">10332</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2025"
      decimals="0"
      id="ixv-62747"
      unitRef="usd">11161</oef:AccmVal>
    <oef:AccmVal
      contextRef="C000203454_2_AdditionalIndexMember_AsOf_2026"
      decimals="0"
      id="ixv-62748"
      unitRef="usd">11613</oef:AccmVal>
    <oef:AvgAnnlRtrTableTextBlock contextRef="C000203454_ClassMember" id="ixv-814">AVERAGE ANNUAL TOTAL RETURNS:

&#160;

1 Year

5 Year

Life of Fund&#160;A


Fidelity&#xae; Series Treasury Bill Index Fund

4.02%

3.44%

2.76%


Bloomberg U.S. 3-6 Month Treasury Bill Index

4.09%


3.44%


2.77%


Bloomberg U.S. Aggregate Bond Index

4.06%


0.18%


1.96%




A&#160; &#160;From August 17, 2018

&#160;
Visit www.fidelity.com for more recent performance information.&#160;

&#160;


The Fund's past performance is not a good predictor of the Fund's future performance. &#160;The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.





</oef:AvgAnnlRtrTableTextBlock>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_NoLoadClassMember_1YR"
      decimals="INF"
      id="ixv-62749"
      unitRef="pure">0.0402</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_NoLoadClassMember_5YR"
      decimals="INF"
      id="ixv-62750"
      unitRef="pure">0.0344</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_NoLoadClassMember_2025-05-01_2026-04-30"
      decimals="INF"
      id="ixv-62751"
      unitRef="pure">0.0276</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_0_AdditionalIndexMember_1YR"
      decimals="INF"
      id="ixv-62752"
      unitRef="pure">0.0409</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_0_AdditionalIndexMember_5YR"
      decimals="INF"
      id="ixv-62753"
      unitRef="pure">0.0344</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_0_AdditionalIndexMember_LOC"
      decimals="INF"
      id="ixv-62754"
      unitRef="pure">0.0277</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_1_BBIndexMember_1YR"
      decimals="INF"
      id="ixv-62755"
      unitRef="pure">0.0406</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_1_BBIndexMember_5YR"
      decimals="INF"
      id="ixv-62756"
      unitRef="pure">0.0018</oef:AvgAnnlRtrPct>
    <oef:AvgAnnlRtrPct
      contextRef="C000203454_1_BBIndexMember_LOC"
      decimals="INF"
      id="ixv-62757"
      unitRef="pure">0.0196</oef:AvgAnnlRtrPct>
    <oef:PerfInceptionDate
      contextRef="C000203454_Perf_2018-08-17_ClassMember"
      id="ixv-883">2018-08-17</oef:PerfInceptionDate>
    <oef:UpdPerfInfoLocationTextBlock contextRef="C000203454_ClassMember" id="ixv-893">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Visit &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;www.fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; for more recent performance information.&lt;/span&gt;</oef:UpdPerfInfoLocationTextBlock>
    <oef:PerformancePastDoesNotIndicateFuture contextRef="C000203454_ClassMember" id="ixv-905">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;font-weight:normal;"&gt;The Fund's past performance is not a good predictor of the Fund's future performance.&lt;/span&gt;</oef:PerformancePastDoesNotIndicateFuture>
    <oef:NoDeductionOfTaxesTextBlock contextRef="C000203454_ClassMember" id="ixv-909">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.&lt;/span&gt;</oef:NoDeductionOfTaxesTextBlock>
    <oef:AddlFundStatisticsTextBlock contextRef="C000203454_ClassMember" id="ixv-915">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;2,030,384,119&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;23&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;0&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Portfolio Turnover&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;0&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000203454_InstantMember"
      decimals="0"
      id="ixv-62758"
      unitRef="usd">2030384119</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000203454_InstantMember"
      decimals="INF"
      id="ixv-62759"
      unitRef="holding">23</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000203454_ClassMember"
      decimals="0"
      id="ixv-62760"
      unitRef="usd">0</oef:AdvisoryFeesPaidAmt>
    <us-gaap:InvestmentCompanyPortfolioTurnover
      contextRef="C000203454_ClassMember"
      decimals="INF"
      id="ixv-62761"
      unitRef="pure">0</us-gaap:InvestmentCompanyPortfolioTurnover>
    <oef:HoldingsTableTextBlock contextRef="C000203454_ClassMember" id="ixv-990">
&#160;
COUPON DISTRIBUTION 
(% of Fund's net assets)


Zero coupon bonds

99.2

&#160;




&#160;
&#160;
&#160;
U.S. Treasury Obligations

99.2


Short-Term Investments and Net Other Assets (Liabilities)

0.8




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

U.S. Treasury Obligations - 99.2&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Short-Term Investments and Net Other Assets (Liabilities) - 0.8


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000203454_CD_0_Member"
      decimals="INF"
      id="ixv-62762"
      unitRef="pure">0.992</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000203454_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62763"
      unitRef="pure">0.992</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000203454_AA_ShortTermInvestmentsandNetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-62764"
      unitRef="pure">0.008</oef:PctOfNav>
    <oef:LargestHoldingsTableTextBlock contextRef="C000203454_ClassMember" id="ixv-1072">TOP HOLDINGS(% of Fund's net assets)

&#160;

&#160;


US Treasury Bill

99.2


&#160;


&#160;

99.2

&#160;



</oef:LargestHoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000203454_TH_0_Member"
      decimals="INF"
      id="ixv-62765"
      unitRef="pure">0.992</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-1153">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000019231_ClassMember" id="ixv-1165">Fidelity&#xae; Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000019231_ClassMember" id="ixv-1168">Fidelity&#xae; Money Market Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000019231_ClassMember" id="ixv-1172">SPRXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000019231_ClassMember" id="ixv-1191">This annual shareholder report contains information about Fidelity&#xae; Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000019231_ClassMember" id="ixv-1193">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000019231_ClassMember" id="ixv-1198">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000019231_ClassMember" id="ixv-1200">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000019231_ClassMember" id="ixv-1203">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000019231_ClassMember" id="ixv-1206">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000019231_ClassMember" id="ixv-1213">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Money Market Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;43&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.42&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000019231_ClassMember"
      decimals="0"
      id="ixv-62766"
      unitRef="usd">43</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000019231_ClassMember"
      decimals="INF"
      id="ixv-62767"
      unitRef="pure">0.0042</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000019231_ClassMember" id="ixv-1261">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;134,691,553,806&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;266&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;337,385,430&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000019231_InstantMember"
      decimals="0"
      id="ixv-62768"
      unitRef="usd">134691553806</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000019231_InstantMember"
      decimals="INF"
      id="ixv-62769"
      unitRef="holding">266</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000019231_ClassMember"
      decimals="0"
      id="ixv-62770"
      unitRef="usd">337385430</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000019231_ClassMember" id="ixv-1325">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

53.8

&#160;


8-30

7.9

&#160;


31-60

12.1

&#160;


61-90

15.0

&#160;


91-180

12.9

&#160;


&gt;180

0.6

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

50.9


U.S. Treasury Obligations

32.6


Commercial Paper

8.4


Time Deposits

5.6


Certificates of Deposit

4.8




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 50.9&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 32.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Commercial Paper - 8.4&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Time Deposits - 5.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Certificates of Deposit - 4.8&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (2.3)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000019231_EMD_0_Member"
      decimals="INF"
      id="ixv-62771"
      unitRef="pure">0.538</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_EMD_1_Member"
      decimals="INF"
      id="ixv-62772"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_EMD_2_Member"
      decimals="INF"
      id="ixv-62773"
      unitRef="pure">0.121</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_EMD_3_Member"
      decimals="INF"
      id="ixv-62774"
      unitRef="pure">0.150</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_EMD_4_Member"
      decimals="INF"
      id="ixv-62775"
      unitRef="pure">0.129</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_EMD_5_Member"
      decimals="INF"
      id="ixv-62776"
      unitRef="pure">0.006</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62777"
      unitRef="pure">0.509</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62778"
      unitRef="pure">0.326</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_AA_CommercialPaper_Member"
      decimals="INF"
      id="ixv-62779"
      unitRef="pure">0.084</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_AA_TimeDeposits_Member"
      decimals="INF"
      id="ixv-62780"
      unitRef="pure">0.056</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019231_AA_CertificatesofDeposit_Member"
      decimals="INF"
      id="ixv-62781"
      unitRef="pure">0.048</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-1557">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000154306_ClassMember" id="ixv-1569">Fidelity&#xae; Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000154306_ClassMember" id="ixv-1572">Fidelity&#xae; Money Market Fund Premium Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000154306_ClassMember" id="ixv-1576">FZDXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000154306_ClassMember" id="ixv-1595">This annual shareholder report contains information about Fidelity&#xae; Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000154306_ClassMember" id="ixv-1597">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000154306_ClassMember" id="ixv-1602">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000154306_ClassMember" id="ixv-1604">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000154306_ClassMember" id="ixv-1607">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000154306_ClassMember" id="ixv-1610">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000154306_ClassMember" id="ixv-1617">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Premium Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;31&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.30&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000154306_ClassMember"
      decimals="0"
      id="ixv-62782"
      unitRef="usd">31</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000154306_ClassMember"
      decimals="INF"
      id="ixv-62783"
      unitRef="pure">0.0030</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000154306_ClassMember" id="ixv-1665">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;134,691,553,806&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;266&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;337,385,430&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000154306_InstantMember"
      decimals="0"
      id="ixv-62784"
      unitRef="usd">134691553806</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000154306_InstantMember"
      decimals="INF"
      id="ixv-62785"
      unitRef="holding">266</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000154306_ClassMember"
      decimals="0"
      id="ixv-62786"
      unitRef="usd">337385430</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000154306_ClassMember" id="ixv-1729">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

53.8

&#160;


8-30

7.9

&#160;


31-60

12.1

&#160;


61-90

15.0

&#160;


91-180

12.9

&#160;


&gt;180

0.6

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

50.9


U.S. Treasury Obligations

32.6


Commercial Paper

8.4


Time Deposits

5.6


Certificates of Deposit

4.8




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 50.9&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 32.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Commercial Paper - 8.4&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Time Deposits - 5.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Certificates of Deposit - 4.8&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (2.3)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000154306_EMD_0_Member"
      decimals="INF"
      id="ixv-62787"
      unitRef="pure">0.538</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_EMD_1_Member"
      decimals="INF"
      id="ixv-62788"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_EMD_2_Member"
      decimals="INF"
      id="ixv-62789"
      unitRef="pure">0.121</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_EMD_3_Member"
      decimals="INF"
      id="ixv-62790"
      unitRef="pure">0.150</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_EMD_4_Member"
      decimals="INF"
      id="ixv-62791"
      unitRef="pure">0.129</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_EMD_5_Member"
      decimals="INF"
      id="ixv-62792"
      unitRef="pure">0.006</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62793"
      unitRef="pure">0.509</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62794"
      unitRef="pure">0.326</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_AA_CommercialPaper_Member"
      decimals="INF"
      id="ixv-62795"
      unitRef="pure">0.084</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_AA_TimeDeposits_Member"
      decimals="INF"
      id="ixv-62796"
      unitRef="pure">0.056</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154306_AA_CertificatesofDeposit_Member"
      decimals="INF"
      id="ixv-62797"
      unitRef="pure">0.048</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-1961">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000019230_ClassMember" id="ixv-1973">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000019230_ClassMember" id="ixv-1976">Fidelity&#xae; Government Money Market Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000019230_ClassMember" id="ixv-1980">SPAXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000019230_ClassMember" id="ixv-1999">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000019230_ClassMember" id="ixv-2001">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000019230_ClassMember" id="ixv-2006">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000019230_ClassMember" id="ixv-2008">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000019230_ClassMember" id="ixv-2011">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000019230_ClassMember" id="ixv-2014">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000019230_ClassMember" id="ixv-2021">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Government Money Market Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;43&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.42&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000019230_ClassMember"
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    <oef:ExpenseRatioPct
      contextRef="C000019230_ClassMember"
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      unitRef="pure">0.0042</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000019230_ClassMember" id="ixv-2069">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000019230_InstantMember"
      decimals="0"
      id="ixv-62800"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000019230_InstantMember"
      decimals="INF"
      id="ixv-62801"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000019230_ClassMember"
      decimals="0"
      id="ixv-62802"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000019230_ClassMember" id="ixv-2133">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000019230_EMD_0_Member"
      decimals="INF"
      id="ixv-62803"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_EMD_1_Member"
      decimals="INF"
      id="ixv-62804"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_EMD_2_Member"
      decimals="INF"
      id="ixv-62805"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_EMD_3_Member"
      decimals="INF"
      id="ixv-62806"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_EMD_4_Member"
      decimals="INF"
      id="ixv-62807"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_EMD_5_Member"
      decimals="INF"
      id="ixv-62808"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62809"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62810"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019230_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62811"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-2339">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000154305_ClassMember" id="ixv-2351">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000154305_ClassMember" id="ixv-2354">Fidelity&#xae; Government Money Market Fund Premium Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000154305_ClassMember" id="ixv-2358">FZCXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000154305_ClassMember" id="ixv-2377">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000154305_ClassMember" id="ixv-2379">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000154305_ClassMember" id="ixv-2384">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000154305_ClassMember" id="ixv-2386">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000154305_ClassMember" id="ixv-2389">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000154305_ClassMember" id="ixv-2392">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000154305_ClassMember" id="ixv-2399">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Premium Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;33&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.32&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000154305_ClassMember"
      decimals="0"
      id="ixv-62812"
      unitRef="usd">33</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000154305_ClassMember"
      decimals="INF"
      id="ixv-62813"
      unitRef="pure">0.0032</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000154305_ClassMember" id="ixv-2447">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000154305_InstantMember"
      decimals="0"
      id="ixv-62814"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000154305_InstantMember"
      decimals="INF"
      id="ixv-62815"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000154305_ClassMember"
      decimals="0"
      id="ixv-62816"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000154305_ClassMember" id="ixv-2511">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000154305_EMD_0_Member"
      decimals="INF"
      id="ixv-62817"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_EMD_1_Member"
      decimals="INF"
      id="ixv-62818"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_EMD_2_Member"
      decimals="INF"
      id="ixv-62819"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_EMD_3_Member"
      decimals="INF"
      id="ixv-62820"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_EMD_4_Member"
      decimals="INF"
      id="ixv-62821"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_EMD_5_Member"
      decimals="INF"
      id="ixv-62822"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62823"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62824"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154305_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62825"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-2717">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000154304_ClassMember" id="ixv-2729">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000154304_ClassMember" id="ixv-2732">Fidelity&#xae; Government Money Market Fund Daily Money Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000154304_ClassMember" id="ixv-2736">FZBXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000154304_ClassMember" id="ixv-2755">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000154304_ClassMember" id="ixv-2757">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000154304_ClassMember" id="ixv-2762">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-208-0098 or by sending an e-mail to funddocuments@fmr.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000154304_ClassMember" id="ixv-2764">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000154304_ClassMember" id="ixv-2767">1-877-208-0098</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000154304_ClassMember" id="ixv-2770">funddocuments@fmr.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000154304_ClassMember" id="ixv-2777">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Daily Money Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;71&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.70&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000154304_ClassMember"
      decimals="0"
      id="ixv-62826"
      unitRef="usd">71</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000154304_ClassMember"
      decimals="INF"
      id="ixv-62827"
      unitRef="pure">0.0070</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000154304_ClassMember" id="ixv-2825">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000154304_InstantMember"
      decimals="0"
      id="ixv-62828"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000154304_InstantMember"
      decimals="INF"
      id="ixv-62829"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000154304_ClassMember"
      decimals="0"
      id="ixv-62830"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000154304_ClassMember" id="ixv-2889">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000154304_EMD_0_Member"
      decimals="INF"
      id="ixv-62831"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_EMD_1_Member"
      decimals="INF"
      id="ixv-62832"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_EMD_2_Member"
      decimals="INF"
      id="ixv-62833"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_EMD_3_Member"
      decimals="INF"
      id="ixv-62834"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_EMD_4_Member"
      decimals="INF"
      id="ixv-62835"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_EMD_5_Member"
      decimals="INF"
      id="ixv-62836"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62837"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62838"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154304_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62839"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-3095">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000232685_ClassMember" id="ixv-3107">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000232685_ClassMember" id="ixv-3110">Fidelity&#xae; Government Money Market Fund Class S</oef:ClassName>
    <dei:TradingSymbol contextRef="C000232685_ClassMember" id="ixv-3114">FZSXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000232685_ClassMember" id="ixv-3133">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000232685_ClassMember" id="ixv-3135">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000232685_ClassMember" id="ixv-3140">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000232685_ClassMember" id="ixv-3142">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000232685_ClassMember" id="ixv-3145">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000232685_ClassMember" id="ixv-3148">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000232685_ClassMember" id="ixv-3155">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Class S&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;43&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.42&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
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    <oef:ExpenseRatioPct
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    <oef:AddlFundStatisticsTextBlock contextRef="C000232685_ClassMember" id="ixv-3203">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000232685_InstantMember"
      decimals="0"
      id="ixv-62842"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
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      id="ixv-62843"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
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      decimals="0"
      id="ixv-62844"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000232685_ClassMember" id="ixv-3267">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000232685_EMD_0_Member"
      decimals="INF"
      id="ixv-62845"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_EMD_1_Member"
      decimals="INF"
      id="ixv-62846"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_EMD_2_Member"
      decimals="INF"
      id="ixv-62847"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_EMD_3_Member"
      decimals="INF"
      id="ixv-62848"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_EMD_4_Member"
      decimals="INF"
      id="ixv-62849"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_EMD_5_Member"
      decimals="INF"
      id="ixv-62850"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62851"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62852"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000232685_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62853"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-3473">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000198393_ClassMember" id="ixv-3485">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000198393_ClassMember" id="ixv-3488">Fidelity&#xae; Government Money Market Fund Class K6</oef:ClassName>
    <dei:TradingSymbol contextRef="C000198393_ClassMember" id="ixv-3492">FNBXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000198393_ClassMember" id="ixv-3511">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000198393_ClassMember" id="ixv-3513">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000198393_ClassMember" id="ixv-3518">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-835-5092 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000198393_ClassMember" id="ixv-3520">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000198393_ClassMember" id="ixv-3523">1-800-835-5092</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000198393_ClassMember" id="ixv-3526">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000198393_ClassMember" id="ixv-3533">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Class K6&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;26&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.25&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000198393_ClassMember"
      decimals="0"
      id="ixv-62854"
      unitRef="usd">26</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000198393_ClassMember"
      decimals="INF"
      id="ixv-62855"
      unitRef="pure">0.0025</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000198393_ClassMember" id="ixv-3581">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000198393_InstantMember"
      decimals="0"
      id="ixv-62856"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000198393_InstantMember"
      decimals="INF"
      id="ixv-62857"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000198393_ClassMember"
      decimals="0"
      id="ixv-62858"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000198393_ClassMember" id="ixv-3645">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000198393_EMD_0_Member"
      decimals="INF"
      id="ixv-62859"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_EMD_1_Member"
      decimals="INF"
      id="ixv-62860"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_EMD_2_Member"
      decimals="INF"
      id="ixv-62861"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_EMD_3_Member"
      decimals="INF"
      id="ixv-62862"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_EMD_4_Member"
      decimals="INF"
      id="ixv-62863"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_EMD_5_Member"
      decimals="INF"
      id="ixv-62864"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62865"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62866"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000198393_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62867"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-3851">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000154303_ClassMember" id="ixv-3863">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000154303_ClassMember" id="ixv-3866">Fidelity&#xae; Government Money Market Fund Capital Reserves Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000154303_ClassMember" id="ixv-3870">FZAXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000154303_ClassMember" id="ixv-3889">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000154303_ClassMember" id="ixv-3891">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000154303_ClassMember" id="ixv-3896">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-208-0098 or by sending an e-mail to funddocuments@fmr.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000154303_ClassMember" id="ixv-3898">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000154303_ClassMember" id="ixv-3901">1-877-208-0098</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000154303_ClassMember" id="ixv-3904">funddocuments@fmr.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000154303_ClassMember" id="ixv-3911">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Capital Reserves Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;97&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.95&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000154303_ClassMember"
      decimals="0"
      id="ixv-62868"
      unitRef="usd">97</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000154303_ClassMember"
      decimals="INF"
      id="ixv-62869"
      unitRef="pure">0.0095</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000154303_ClassMember" id="ixv-3959">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000154303_InstantMember"
      decimals="0"
      id="ixv-62870"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000154303_InstantMember"
      decimals="INF"
      id="ixv-62871"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000154303_ClassMember"
      decimals="0"
      id="ixv-62872"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000154303_ClassMember" id="ixv-4023">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000154303_EMD_0_Member"
      decimals="INF"
      id="ixv-62873"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_EMD_1_Member"
      decimals="INF"
      id="ixv-62874"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_EMD_2_Member"
      decimals="INF"
      id="ixv-62875"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_EMD_3_Member"
      decimals="INF"
      id="ixv-62876"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_EMD_4_Member"
      decimals="INF"
      id="ixv-62877"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_EMD_5_Member"
      decimals="INF"
      id="ixv-62878"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62879"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62880"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000154303_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62881"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-4229">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000190683_ClassMember" id="ixv-4241">Fidelity&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000190683_ClassMember" id="ixv-4244">Fidelity&#xae; Government Money Market Fund Advisor M Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000190683_ClassMember" id="ixv-4248">FZGXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000190683_ClassMember" id="ixv-4267">This annual shareholder report contains information about Fidelity&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000190683_ClassMember" id="ixv-4269">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000190683_ClassMember" id="ixv-4274">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-208-0098 or by sending an e-mail to funddocuments@fmr.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000190683_ClassMember" id="ixv-4276">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000190683_ClassMember" id="ixv-4279">1-877-208-0098</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000190683_ClassMember" id="ixv-4282">funddocuments@fmr.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000190683_ClassMember" id="ixv-4289">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Advisor M Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;71&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.70&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
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    <oef:ExpenseRatioPct
      contextRef="C000190683_ClassMember"
      decimals="INF"
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      unitRef="pure">0.0070</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000190683_ClassMember" id="ixv-4337">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;452,711,941,602&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;744&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,063,880,910&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000190683_InstantMember"
      decimals="0"
      id="ixv-62884"
      unitRef="usd">452711941602</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000190683_InstantMember"
      decimals="INF"
      id="ixv-62885"
      unitRef="holding">744</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
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      decimals="0"
      id="ixv-62886"
      unitRef="usd">1063880910</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000190683_ClassMember" id="ixv-4401">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

62.9

&#160;


8-30

7.9

&#160;


31-60

5.3

&#160;


61-90

7.6

&#160;


91-180

10.4

&#160;


&gt;180

7.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

41.0


U.S. Government Agency - Debt

31.6


U.S. Treasury Obligations

28.6




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 41.0&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 31.6&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 28.6&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (1.2)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000190683_EMD_0_Member"
      decimals="INF"
      id="ixv-62887"
      unitRef="pure">0.629</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_EMD_1_Member"
      decimals="INF"
      id="ixv-62888"
      unitRef="pure">0.079</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_EMD_2_Member"
      decimals="INF"
      id="ixv-62889"
      unitRef="pure">0.053</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_EMD_3_Member"
      decimals="INF"
      id="ixv-62890"
      unitRef="pure">0.076</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_EMD_4_Member"
      decimals="INF"
      id="ixv-62891"
      unitRef="pure">0.104</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_EMD_5_Member"
      decimals="INF"
      id="ixv-62892"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62893"
      unitRef="pure">0.410</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62894"
      unitRef="pure">0.316</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000190683_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62895"
      unitRef="pure">0.286</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-4607">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:MaterialFundChngNoticeTextBlock contextRef="C000177594_ClassMember" id="ixv-4611">This report describes changes to the Fund that occurred during the reporting period.</oef:MaterialFundChngNoticeTextBlock>
    <oef:FundName contextRef="C000177594_ClassMember" id="ixv-4622">Fidelity Flex&#xae; Government Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000177594_ClassMember" id="ixv-4625">Fidelity Flex&#xae; Government Money Market Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000177594_ClassMember" id="ixv-4629">FLGXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000177594_ClassMember" id="ixv-4648">This annual shareholder report contains information about Fidelity Flex&#xae; Government Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000177594_ClassMember" id="ixv-4650">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000177594_ClassMember" id="ixv-4655">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000177594_ClassMember" id="ixv-4657">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000177594_ClassMember" id="ixv-4660">1-800-544-3455</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000177594_ClassMember" id="ixv-4663">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000177594_ClassMember" id="ixv-4670">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity Flex&#xae; Government Money Market Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;0&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.00&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;B&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans Cd';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Amount represents less than $.50&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;B &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans Cd';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Amount represents less than 0.005%&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000177594_ClassMember"
      decimals="0"
      id="ixv-62896"
      unitRef="usd">0</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000177594_ClassMember"
      decimals="INF"
      id="ixv-62897"
      unitRef="pure">0.0000</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000177594_ClassMember" id="ixv-4728">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;221,277,787&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;173&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;0&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000177594_InstantMember"
      decimals="0"
      id="ixv-62898"
      unitRef="usd">221277787</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000177594_InstantMember"
      decimals="INF"
      id="ixv-62899"
      unitRef="holding">173</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
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      decimals="0"
      id="ixv-62900"
      unitRef="usd">0</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000177594_ClassMember" id="ixv-4792">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

59.4

&#160;


8-30

8.2

&#160;


31-60

5.5

&#160;


61-90

7.1

&#160;


91-180

15.2

&#160;


&gt;180

4.1

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
Repurchase Agreements

38.3


U.S. Government Agency - Debt

33.8


U.S. Treasury Obligations

27.4


Net Other Assets (Liabilities)

0.5




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

Repurchase Agreements - 38.3&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

U.S. Government Agency - Debt - 33.8&#160;&#160;&#160;&#160;


&#160;

U.S. Treasury Obligations - 27.4&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;


&#160;

Net Other Assets (Liabilities) - 0.5&#160;&#160;&#160;&#160;


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
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      decimals="INF"
      id="ixv-62901"
      unitRef="pure">0.594</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_EMD_1_Member"
      decimals="INF"
      id="ixv-62902"
      unitRef="pure">0.082</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_EMD_2_Member"
      decimals="INF"
      id="ixv-62903"
      unitRef="pure">0.055</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_EMD_3_Member"
      decimals="INF"
      id="ixv-62904"
      unitRef="pure">0.071</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_EMD_4_Member"
      decimals="INF"
      id="ixv-62905"
      unitRef="pure">0.152</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_EMD_5_Member"
      decimals="INF"
      id="ixv-62906"
      unitRef="pure">0.041</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_AA_RepurchaseAgreements_Member"
      decimals="INF"
      id="ixv-62907"
      unitRef="pure">0.383</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_AA_USGovernmentAgencyDebt_Member"
      decimals="INF"
      id="ixv-62908"
      unitRef="pure">0.338</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62909"
      unitRef="pure">0.274</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000177594_AA_NetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-62910"
      unitRef="pure">0.005</oef:PctOfNav>
    <oef:MaterialFundChngTextBlock contextRef="C000177594_ClassMember" id="ixv-4961">
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;How has the Fund changed?&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-3455&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:50%; background-color:#ebf3e9;border-right:2px dashed #368627;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund's contractual proxy and shareholder meeting expense cap expired during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:50%; background-color:#ebf3e9;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngTextBlock>
    <oef:SummaryOfChngLegendTextBlock contextRef="C000177594_ClassMember" id="ixv-4967">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-3455&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;</oef:SummaryOfChngLegendTextBlock>
    <oef:UpdProspectusWebAddress contextRef="C000177594_ClassMember" id="ixv-4969">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;</oef:UpdProspectusWebAddress>
    <oef:UpdProspectusPhoneNumber contextRef="C000177594_ClassMember" id="ixv-4972">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-800-544-3455&lt;/span&gt;</oef:UpdProspectusPhoneNumber>
    <oef:UpdProspectusEmailAddress contextRef="C000177594_ClassMember" id="ixv-4976">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;</oef:UpdProspectusEmailAddress>
    <oef:MaterialFundChngExpensesTextBlock contextRef="C000177594_ClassMember" id="ixv-4987">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund's contractual proxy and shareholder meeting expense cap expired during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngExpensesTextBlock>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-5044">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:MaterialFundChngNoticeTextBlock contextRef="C000255665_ClassMember" id="ixv-5048">This report describes changes to the Fund that occurred during the reporting period.</oef:MaterialFundChngNoticeTextBlock>
    <oef:FundName contextRef="C000255665_ClassMember" id="ixv-5059">Fidelity&#xae; Treasury Digital Fund</oef:FundName>
    <oef:ClassName contextRef="C000255665_ClassMember" id="ixv-5062">Fidelity&#xae; Treasury Digital Fund Liquidity</oef:ClassName>
    <dei:TradingSymbol contextRef="C000255665_ClassMember" id="ixv-5066">FYHXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000255665_ClassMember" id="ixv-5085">This annual shareholder report contains information about Fidelity&#xae; Treasury Digital Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000255665_ClassMember" id="ixv-5087">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000255665_ClassMember" id="ixv-5092">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-297-2952 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000255665_ClassMember" id="ixv-5094">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000255665_ClassMember" id="ixv-5097">1-877-297-2952</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000255665_ClassMember" id="ixv-5100">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000255665_ClassMember" id="ixv-5107">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Liquidity&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;19&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.18&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000255665_ClassMember"
      decimals="0"
      id="ixv-62911"
      unitRef="usd">19</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000255665_ClassMember"
      decimals="INF"
      id="ixv-62912"
      unitRef="pure">0.0018</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000255665_ClassMember" id="ixv-5155">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;171,679,853&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;17&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;621,595&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000255665_InstantMember"
      decimals="0"
      id="ixv-62913"
      unitRef="usd">171679853</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000255665_InstantMember"
      decimals="INF"
      id="ixv-62914"
      unitRef="holding">17</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000255665_ClassMember"
      decimals="0"
      id="ixv-62915"
      unitRef="usd">621595</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000255665_ClassMember" id="ixv-5219">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

10.5

&#160;


8-30

24.2

&#160;


31-60

38.5

&#160;


61-90

31.5

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
U.S. Treasury Obligations

104.7




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

U.S. Treasury Obligations - 104.7&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (4.7)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000255665_EMD_0_Member"
      decimals="INF"
      id="ixv-62916"
      unitRef="pure">0.105</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000255665_EMD_1_Member"
      decimals="INF"
      id="ixv-62917"
      unitRef="pure">0.242</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000255665_EMD_2_Member"
      decimals="INF"
      id="ixv-62918"
      unitRef="pure">0.385</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000255665_EMD_3_Member"
      decimals="INF"
      id="ixv-62919"
      unitRef="pure">0.315</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000255665_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62920"
      unitRef="pure">1.047</oef:PctOfNav>
    <oef:MaterialFundChngTextBlock contextRef="C000255665_ClassMember" id="ixv-5335">
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;How has the Fund changed?&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:50%; background-color:#ebf3e9;border-right:2px dashed #368627;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:50%; background-color:#ebf3e9;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngTextBlock>
    <oef:SummaryOfChngLegendTextBlock contextRef="C000255665_ClassMember" id="ixv-5341">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;</oef:SummaryOfChngLegendTextBlock>
    <oef:UpdProspectusWebAddress contextRef="C000255665_ClassMember" id="ixv-5343">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;</oef:UpdProspectusWebAddress>
    <oef:UpdProspectusPhoneNumber contextRef="C000255665_ClassMember" id="ixv-5346">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;</oef:UpdProspectusPhoneNumber>
    <oef:UpdProspectusEmailAddress contextRef="C000255665_ClassMember" id="ixv-5350">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;</oef:UpdProspectusEmailAddress>
    <oef:MaterialFundChngStrategiesTextBlock contextRef="C000255665_ClassMember" id="ixv-5361">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngStrategiesTextBlock>
    <oef:MaterialFundChngRisksChngTextBlock contextRef="C000255665_ClassMember" id="ixv-5367">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;</oef:MaterialFundChngRisksChngTextBlock>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-5423">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:MaterialFundChngNoticeTextBlock contextRef="C000257340_ClassMember" id="ixv-5427">This report describes changes to the Fund that occurred during the reporting period.</oef:MaterialFundChngNoticeTextBlock>
    <oef:FundName contextRef="C000257340_ClassMember" id="ixv-5438">Fidelity&#xae; Treasury Only Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000257340_ClassMember" id="ixv-5441">Fidelity&#xae; Treasury Only Money Market Fund Class OUS</oef:ClassName>
    <dei:TradingSymbol contextRef="C000257340_ClassMember" id="ixv-5445">FYIXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000257340_ClassMember" id="ixv-5464">This annual shareholder report contains information about Fidelity&#xae; Treasury Only Money Market Fund for the period May 1, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000257340_ClassMember" id="ixv-5466">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000257340_ClassMember" id="ixv-5471">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 800-544-0275 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000257340_ClassMember" id="ixv-5473">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000257340_ClassMember" id="ixv-5476">800-544-0275</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000257340_ClassMember" id="ixv-5479">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000257340_ClassMember" id="ixv-5486">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Class OUS&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;38&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.37&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000257340_ClassMember"
      decimals="0"
      id="ixv-62921"
      unitRef="usd">38</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000257340_ClassMember"
      decimals="INF"
      id="ixv-62922"
      unitRef="pure">0.0037</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000257340_ClassMember" id="ixv-5534">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;16,940,567,988&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;57&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;61,283,591&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000257340_InstantMember"
      decimals="0"
      id="ixv-62923"
      unitRef="usd">16940567988</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000257340_InstantMember"
      decimals="INF"
      id="ixv-62924"
      unitRef="holding">57</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000257340_ClassMember"
      decimals="0"
      id="ixv-62925"
      unitRef="usd">61283591</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000257340_ClassMember" id="ixv-5598">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

19.9

&#160;


8-30

17.9

&#160;


31-60

24.1

&#160;


61-90

21.0

&#160;


91-180

16.4

&#160;


&gt;180

1.6

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
U.S. Treasury Obligations

100.9




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

U.S. Treasury Obligations - 100.9&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (0.9)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000257340_EMD_0_Member"
      decimals="INF"
      id="ixv-62926"
      unitRef="pure">0.199</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_EMD_1_Member"
      decimals="INF"
      id="ixv-62927"
      unitRef="pure">0.179</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_EMD_2_Member"
      decimals="INF"
      id="ixv-62928"
      unitRef="pure">0.241</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_EMD_3_Member"
      decimals="INF"
      id="ixv-62929"
      unitRef="pure">0.210</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_EMD_4_Member"
      decimals="INF"
      id="ixv-62930"
      unitRef="pure">0.164</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_EMD_5_Member"
      decimals="INF"
      id="ixv-62931"
      unitRef="pure">0.016</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000257340_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62932"
      unitRef="pure">1.009</oef:PctOfNav>
    <oef:MaterialFundChngTextBlock contextRef="C000257340_ClassMember" id="ixv-5732">
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;How has the Fund changed?&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;800-544-0275&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:50%; background-color:#ebf3e9;border-right:2px dashed #368627;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:50%; background-color:#ebf3e9;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngTextBlock>
    <oef:SummaryOfChngLegendTextBlock contextRef="C000257340_ClassMember" id="ixv-5738">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since May 1, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;800-544-0275&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;</oef:SummaryOfChngLegendTextBlock>
    <oef:UpdProspectusWebAddress contextRef="C000257340_ClassMember" id="ixv-5742">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;</oef:UpdProspectusWebAddress>
    <oef:UpdProspectusPhoneNumber contextRef="C000257340_ClassMember" id="ixv-5745">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;800-544-0275&lt;/span&gt;</oef:UpdProspectusPhoneNumber>
    <oef:UpdProspectusEmailAddress contextRef="C000257340_ClassMember" id="ixv-5749">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;</oef:UpdProspectusEmailAddress>
    <oef:MaterialFundChngStrategiesTextBlock contextRef="C000257340_ClassMember" id="ixv-5760">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngStrategiesTextBlock>
    <oef:MaterialFundChngRisksChngTextBlock contextRef="C000257340_ClassMember" id="ixv-5767">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;</oef:MaterialFundChngRisksChngTextBlock>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-5823">2026-04-30</dei:DocumentPeriodEndDate>
    <oef:MaterialFundChngNoticeTextBlock contextRef="C000261149_ClassMember" id="ixv-5827">This report describes changes to the Fund that occurred during the reporting period.</oef:MaterialFundChngNoticeTextBlock>
    <oef:FundName contextRef="C000261149_ClassMember" id="ixv-5838">Fidelity&#xae; Treasury Digital Fund</oef:FundName>
    <oef:ClassName contextRef="C000261149_ClassMember" id="ixv-5841">Fidelity&#xae; Treasury Digital Fund OnChain</oef:ClassName>
    <dei:TradingSymbol contextRef="C000261149_ClassMember" id="ixv-5845">FYOXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000261149_ClassMember" id="ixv-5864">This annual shareholder report contains information about Fidelity&#xae; Treasury Digital Fund for the period August 4, 2025 to April 30, 2026.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000261149_ClassMember" id="ixv-5866">annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000261149_ClassMember" id="ixv-5871">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-297-2952 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000261149_ClassMember" id="ixv-5873">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000261149_ClassMember" id="ixv-5876">1-877-297-2952</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000261149_ClassMember" id="ixv-5879">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000261149_ClassMember" id="ixv-5886">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last year?&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;FUND COST (PREVIOUS YEAR)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:51%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:51%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;OnChain&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:21%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;15&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:27%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;text-align-last:auto;"&gt;0.20&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:6px;color:#000000;font-style:normal;vertical-align:4px;font-weight:normal;"&gt;A&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans Cd';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Expenses for the full reporting period would be higher.&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000261149_ClassMember"
      decimals="0"
      id="ixv-62933"
      unitRef="usd">15</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000261149_ClassMember"
      decimals="INF"
      id="ixv-62934"
      unitRef="pure">0.0020</oef:ExpenseRatioPct>
    <oef:ExpensesShortPeriodFnTextBlock contextRef="C000261149_ClassMember" id="ixv-5929">Expenses for the full reporting period would be higher.</oef:ExpensesShortPeriodFnTextBlock>
    <oef:AddlFundStatisticsTextBlock contextRef="C000261149_ClassMember" id="ixv-5941">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of April 30, 2026)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt; &lt;span&gt;&#160;&lt;/span&gt;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;171,679,853&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;17&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Total Advisory Fee&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;621,595&lt;/div&gt;
&lt;div style="text-align:right;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="middle"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000261149_InstantMember"
      decimals="0"
      id="ixv-62935"
      unitRef="usd">171679853</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000261149_InstantMember"
      decimals="INF"
      id="ixv-62936"
      unitRef="holding">17</oef:HoldingsCount>
    <oef:AdvisoryFeesPaidAmt
      contextRef="C000261149_ClassMember"
      decimals="0"
      id="ixv-62937"
      unitRef="usd">621595</oef:AdvisoryFeesPaidAmt>
    <oef:HoldingsTableTextBlock contextRef="C000261149_ClassMember" id="ixv-6005">
&#160;
EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

10.5

&#160;


8-30

24.2

&#160;


31-60

38.5

&#160;


61-90

31.5

&#160;


&#160;
&#160;




&#160;
&#160;
&#160;
U.S. Treasury Obligations

104.7




ASSET ALLOCATION (% of Fund's net assets)


&#160;



&#160;

U.S. Treasury Obligations - 104.7&#160;&#160;&#160;&#160;&#160;&#160;&#160;


Net Other Assets (Liabilities) - (4.7)%


&#160;






</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000261149_EMD_0_Member"
      decimals="INF"
      id="ixv-62938"
      unitRef="pure">0.105</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000261149_EMD_1_Member"
      decimals="INF"
      id="ixv-62939"
      unitRef="pure">0.242</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000261149_EMD_2_Member"
      decimals="INF"
      id="ixv-62940"
      unitRef="pure">0.385</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000261149_EMD_3_Member"
      decimals="INF"
      id="ixv-62941"
      unitRef="pure">0.315</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000261149_AA_USTreasuryObligations_Member"
      decimals="INF"
      id="ixv-62942"
      unitRef="pure">1.047</oef:PctOfNav>
    <oef:MaterialFundChngTextBlock contextRef="C000261149_ClassMember" id="ixv-6121">
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;How has the Fund changed?&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since August 4, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:50%; background-color:#ebf3e9;border-right:2px dashed #368627;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:50%; background-color:#ebf3e9;padding:19px 19px 19px 19px;" valign="top"&gt;&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngTextBlock>
    <oef:SummaryOfChngLegendTextBlock contextRef="C000261149_ClassMember" id="ixv-6127">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;This is a summary of certain changes to the Fund since August 4, 2025. For more complete information, you may review the Fund's next prospectus, which we expect to be available by June 27, 2026 at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or upon request at &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:0px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt; or by sending an e-mail to &lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;.&lt;/span&gt;</oef:SummaryOfChngLegendTextBlock>
    <oef:UpdProspectusWebAddress contextRef="C000261149_ClassMember" id="ixv-6129">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;fundresearch.fidelity.com/prospectus/sec&lt;/span&gt;</oef:UpdProspectusWebAddress>
    <oef:UpdProspectusPhoneNumber contextRef="C000261149_ClassMember" id="ixv-6132">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;1-877-297-2952&lt;/span&gt;</oef:UpdProspectusPhoneNumber>
    <oef:UpdProspectusEmailAddress contextRef="C000261149_ClassMember" id="ixv-6136">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;fidfunddocuments@fidelity.com&lt;/span&gt;</oef:UpdProspectusEmailAddress>
    <oef:MaterialFundChngStrategiesTextBlock contextRef="C000261149_ClassMember" id="ixv-6147">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment strategies during the reporting period.&lt;/span&gt;

&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;/div&gt;</oef:MaterialFundChngStrategiesTextBlock>
    <oef:MaterialFundChngRisksChngTextBlock contextRef="C000261149_ClassMember" id="ixv-6153">&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;The fund modified its principal investment risks during the reporting period.&lt;/span&gt;
&lt;div style="text-align:left;text-align-last:auto;"&gt;&lt;br/&gt;&lt;/div&gt;</oef:MaterialFundChngRisksChngTextBlock>
</xbrl>
