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      xml:lang="en-US">&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;This &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;semi-annual shareholder report&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt; contains important information about &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;Western Asset Premier Institutional Government Reserves for &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;the period &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;September 1, 2025, to &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;February 28, 2026.&lt;/span&gt;</oef:AnnlOrSemiAnnlStatementTextBlock>
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      xml:lang="en-US">&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;You can find additional information about the Fund at &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;https://www.franklintempleton.com/regulatory-fund-documents&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;. You can also &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;request this information by contacting us at &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;1-800-625-4554, or 1-203-703-6002&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;.&lt;/span&gt;</oef:AddlInfoTextBlock>
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      xml:lang="en-US">&lt;div&gt;&lt;span style="text-transform:uppercase;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;text-transform:uppercase;color:#1447FF;;"&gt;&lt;b&gt;WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? &lt;/b&gt;&lt;/span&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;(based on a hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;&lt;div&gt;
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         &lt;tr&gt;
            &lt;td colspan="1" style="vertical-align:top"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:left;text-align:left;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#2D2D2D;;"&gt;&lt;b&gt;Total Number of Portfolio Holdings (reflects holdings of &lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#2D2D2D;;"&gt;&lt;b&gt;Government Portfolio)&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="vertical-align:bottom"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:right;text-align:right;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;"&gt;104&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
         &lt;/tr&gt;
      &lt;/table&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
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      contextRef="c_6815_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassCapitalShares_2026-02-28Member"
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      xml:lang="en-US">&lt;div&gt;&lt;span style="text-transform:uppercase;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;text-transform:uppercase;color:#1447FF;;"&gt;&lt;b&gt;WHAT DID THE FUND INVEST IN? &lt;/b&gt;&lt;/span&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;(as of &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;February 28, 2026)&lt;/span&gt;&lt;/div&gt;&lt;div&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;Portfolio Composition&lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;&#160;&#x2009;&lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;(% of Total Investments)&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;&lt;div&gt;&lt;img alt="image" src="ts6815img004.jpg" style="width:96.41294838145232%"/&gt;&lt;/div&gt;</oef:HoldingsTableTextBlock>
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    <oef:PctOfTotalInv
      contextRef="c_6815_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassCapitalShares_2026-02-28_5263Member"
      decimals="INF"
      id="ixv-12573"
      unitRef="RATIO">0.461</oef:PctOfTotalInv>
    <oef:PctOfTotalInv
      contextRef="c_6815_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassCapitalShares_2026-02-28_5267Member"
      decimals="INF"
      id="ixv-12574"
      unitRef="RATIO">0.331</oef:PctOfTotalInv>
    <oef:PctOfTotalInv
      contextRef="c_6815_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassCapitalShares_2026-02-28_5262Member"
      decimals="INF"
      id="ixv-12575"
      unitRef="RATIO">0.141</oef:PctOfTotalInv>
    <oef:PctOfTotalInv
      contextRef="c_6815_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassCapitalShares_2026-02-28_5261Member"
      decimals="INF"
      id="ixv-12576"
      unitRef="RATIO">0.067</oef:PctOfTotalInv>
    <oef:FundName
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      id="ixv-334"
      xml:lang="en-US">Western Asset Premier Institutional Government Reserves</oef:FundName>
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      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
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      xml:lang="en-US">Premium Shares</oef:ClassName>
    <dei:TradingSymbol
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="ixv-343"
      xml:lang="en-US">WACXX</dei:TradingSymbol>
    <dei:DocumentPeriodEndDate
      contextRef="c_6815_duration_WesternAssetPremierInstitutionalGovernmentReserves_2025-09-01_2026-02-28Member"
      id="ixv-349"
      xml:lang="en-US">2026-02-28</dei:DocumentPeriodEndDate>
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      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
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      xml:lang="en-US">&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;This &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;semi-annual shareholder report&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt; contains important information about &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;Western Asset Premier Institutional Government Reserves for &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;the period &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;September 1, 2025, to &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;February 28, 2026.&lt;/span&gt;</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual
      contextRef="c_6815_duration_WesternAssetPremierInstitutionalGovernmentReserves_2025-09-01_2026-02-28Member"
      id="ixv-360"
      xml:lang="en-US">semi-annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock
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      id="ixv-368"
      xml:lang="en-US">&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;You can find additional information about the Fund at &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;https://www.franklintempleton.com/regulatory-fund-documents&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;. You can also &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;request this information by contacting us at &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;1-800-625-4554, or 1-203-703-6002&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#161616;;"&gt;.&lt;/span&gt;</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="ixv-370"
      xml:lang="en-US">https://www.franklintempleton.com/regulatory-fund-documents</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="ixv-374"
      xml:lang="en-US">1-800-625-4554, or 1-203-703-6002</oef:AddlInfoPhoneNumber>
    <oef:ExpensesTextBlock
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="foot-6816_739199-1011"
      xml:lang="en-US">&lt;div&gt;&lt;span style="text-transform:uppercase;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;text-transform:uppercase;color:#1447FF;;"&gt;&lt;b&gt;WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? &lt;/b&gt;&lt;/span&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;(based on a hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;&lt;div&gt;
      &lt;table cellspacing="0" style="width:98%;cellspacing:0;border-top:1.5pt solid #E6FAFF;border-left:1.5pt solid #E6FAFF;  border-right:1.5pt solid #E6FAFF;  border-bottom:1.5pt solid #E6FAFF; margin-left:7.9pt;"&gt;
         &lt;tr style="height:1px;"&gt;
            &lt;td style="height:1px;width:50%;background-color:#E6FAFF;"&gt;&lt;/td&gt;
            &lt;td style="height:1px;width:22.33812949640288%;background-color:#E6FAFF;"&gt;&lt;/td&gt;
            &lt;td style="height:1px;width:27.661870503597125%;background-color:#E6FAFF;"&gt;&lt;/td&gt;
         &lt;/tr&gt;
         &lt;tr&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;border-bottom:1.5pt solid #1447FF;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:left;text-align:left;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;b&gt;Class Name&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;border-bottom:1.5pt solid #1447FF;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:center;text-align:center;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;b&gt;Costs of a $10,000 &lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;b&gt;investment&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;border-bottom:1.5pt solid #1447FF;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:center;text-align:center;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;b&gt;Costs paid as a percentage of a &lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;b&gt;$10,000 investment&lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:7.5pt;;"&gt;&lt;sup&gt;,&lt;/sup&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;&lt;sup&gt;&#x2020;&lt;/sup&gt;&lt;/span&gt;
               &lt;/div&gt;
            &lt;/td&gt;
         &lt;/tr&gt;
         &lt;tr&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:left;text-align:left;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;;"&gt;Premium Shares&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:7.5pt;;"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/span&gt;
               &lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:center;text-align:center;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;"&gt;$7&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="background-color:#E6FAFF;;white-space:nowrap;vertical-align:bottom"&gt;
               &lt;div style="background-color:#E6FAFF;padding-left:2pt;padding-top:1.5pt;padding-bottom:0;align:center;text-align:center;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;"&gt;0.13%&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
         &lt;/tr&gt;
      &lt;/table&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      decimals="INF"
      id="foot-6816_739199-1021"
      unitRef="USD">7</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      decimals="INF"
      id="foot-6816_739199-1031"
      unitRef="RATIO">0.0013</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="ixv-458"
      xml:lang="en-US">&lt;div&gt;&lt;span style="text-transform:uppercase;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;text-transform:uppercase;color:#1447FF;;"&gt;&lt;b&gt;KEY FUND STATISTICS &lt;/b&gt;&lt;/span&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;(as of &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;February 28, 2026)&lt;/span&gt;&lt;/div&gt;&lt;div&gt;
      &lt;table cellspacing="0" style="width:98%;cellspacing:0;border-top:1.5pt solid #6B6B6B;margin-left:7.75pt;border-bottom:1.5pt solid #6B6B6B;margin-top:10px;"&gt;
         &lt;tr style="height:1px;"&gt;
            &lt;td style="height:1px;width:74.41007194244604%;"&gt;&lt;/td&gt;
            &lt;td style="height:1px;width:25.58992805755396%;"&gt;&lt;/td&gt;
         &lt;/tr&gt;
         &lt;tr&gt;
            &lt;td colspan="1" style="border-bottom:0.75pt solid #6B6B6B;vertical-align:top"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:left;text-align:left;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#2D2D2D;;"&gt;&lt;b&gt;Total Net Assets&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="border-bottom:0.75pt solid #6B6B6B;vertical-align:bottom"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:right;text-align:right;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;"&gt;$8,473,315,720&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
         &lt;/tr&gt;
         &lt;tr&gt;
            &lt;td colspan="1" style="vertical-align:top"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:left;text-align:left;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#2D2D2D;;"&gt;&lt;b&gt;Total Number of Portfolio Holdings (reflects holdings of &lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;color:#2D2D2D;;"&gt;&lt;b&gt;Government Portfolio)&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
            &lt;td colspan="1" style="vertical-align:bottom"&gt;
               &lt;div style="background-color:#FFFFFF;padding-left:2pt;padding-top:1pt;padding-bottom:0;align:right;text-align:right;padding-right:2pt;font-family:Arial, Helvetica, sans-serif;font-size:10pt;margin-top:1pt;margin-bottom:0;"&gt;&lt;span style="font-family:Arial, Helvetica, sans-serif;font-size:10.02pt;"&gt;104&lt;/span&gt;&lt;/div&gt;
            &lt;/td&gt;
         &lt;/tr&gt;
      &lt;/table&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="c_6816_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2026-02-28Member"
      decimals="INF"
      id="ixv-12579"
      unitRef="USD">8473315720</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="c_6816_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2026-02-28Member"
      decimals="INF"
      id="ixv-12580"
      unitRef="UNIT">104</oef:HoldingsCount>
    <oef:HoldingsTableTextBlock
      contextRef="c_6816_duration_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2025-09-01_2026-02-28Member"
      id="foot-6816_751573-1011"
      xml:lang="en-US">&lt;div&gt;&lt;span style="text-transform:uppercase;"&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;text-transform:uppercase;color:#1447FF;;"&gt;&lt;b&gt;WHAT DID THE FUND INVEST IN? &lt;/b&gt;&lt;/span&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;(as of &lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:10.824pt;color:#2D2D2D;;"&gt;February 28, 2026)&lt;/span&gt;&lt;/div&gt;&lt;div&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;Portfolio Composition&lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;&#160;&#x2009;&lt;/b&gt;&lt;/span&gt;&lt;span style="clear:both;font-family:Arial, Helvetica, sans-serif;font-size:12.024pt;color:#161616;;"&gt;&lt;b&gt;(% of Total Investments)&lt;/b&gt;&lt;/span&gt;&lt;/div&gt;&lt;div&gt;&lt;img alt="image" src="ts6816img004.jpg" style="width:96.41294838145232%"/&gt;&lt;/div&gt;</oef:HoldingsTableTextBlock>
    <oef:UpdProspectusWebAddress
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      id="ixv-545"
      xml:lang="en-US">https://www.franklintempleton.com/regulatory-fund-documents</oef:UpdProspectusWebAddress>
    <oef:PctOfTotalInv
      contextRef="c_6816_instant_WesternAssetPremierInstitutionalGovernmentReserves_ClassPremiumShares_2026-02-28_4123Member"
      decimals="INF"
      id="ixv-12581"
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