XML 25 R2.htm IDEA: XBRL DOCUMENT v3.25.1
Shareholder Report
 6 Months Ended
Feb. 28, 2025
USD ($)
$ / shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Legg Mason Partners Institutional Trust
Entity Central Index Key 0000889512
Entity Investment Company Type N-1A
Document Period End Date Feb. 28, 2025
Institutional Shares  
Shareholder Report [Line Items]  
Fund Name Western Asset Institutional U.S. Treasury Obligations Money Market Fund
Class Name Institutional Shares
Trading Symbol LUIXX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Western Asset Institutional U.S. Treasury Obligations Money Market Fund for the period September 1, 2024, to February 28, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at 1-800-625-4554, or 1-203-703-6002.
Additional Information Phone Number 1-800-625-4554, or 1-203-703-6002
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Institutional Shares1
$9
0.18%
[1],[2],[3]
Expenses Paid, Amount $ 9 [1]
Expense Ratio, Percent 0.18% [1]
Net Assets $ 476,390,058
Holdings Count | $ / shares 44 [4]
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2025)
Total Net Assets
$476,390,058
Total Number of Portfolio Holdings*
44
[4]
Holdings [Text Block]
image
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Investor Shares  
Shareholder Report [Line Items]  
Fund Name Western Asset Institutional U.S. Treasury Obligations Money Market Fund
Class Name Investor Shares
Trading Symbol LAIXX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Western Asset Institutional U.S. Treasury Obligations Money Market Fund for the period September 1, 2024, to February 28, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at 1-800-625-4554, or 1-203-703-6002.
Additional Information Phone Number 1-800-625-4554, or 1-203-703-6002
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Investor Shares1
$12
0.23%
[5],[6],[7]
Expenses Paid, Amount $ 12 [5]
Expense Ratio, Percent 0.23% [5]
Net Assets $ 476,390,058
Holdings Count | $ / shares 44 [8]
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2025)
Total Net Assets
$476,390,058
Total Number of Portfolio Holdings*
44
[8]
Holdings [Text Block]
image
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Administrative Shares  
Shareholder Report [Line Items]  
Fund Name Western Asset Institutional U.S. Treasury Obligations Money Market Fund
Class Name Administrative Shares
Trading Symbol LAOXX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Western Asset Institutional U.S. Treasury Obligations Money Market Fund for the period September 1, 2024, to February 28, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at 1-800-625-4554, or 1-203-703-6002.
Additional Information Phone Number 1-800-625-4554, or 1-203-703-6002
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Administrative Shares1
$20
0.39%
[9],[10],[11]
Expenses Paid, Amount $ 20 [9]
Expense Ratio, Percent 0.39% [9]
Net Assets $ 476,390,058
Holdings Count | $ / shares 44 [12]
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2025)
Total Net Assets
$476,390,058
Total Number of Portfolio Holdings*
44
[12]
Holdings [Text Block]
image
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
[1]
1 The expense table reflects the expenses of both the feeder Fund and the master Fund.
[2]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. Additional amounts may be voluntarily waived and/or reimbursed from time to time.
[3]
† Annualized.
[4]
* Reflects holdings of U.S. Treasury Obligations Portfolio.
[5]
1 The expense table reflects the expenses of both the feeder Fund and the master Fund.
[6]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. Additional amounts may be voluntarily waived and/or reimbursed from time to time.
[7]
† Annualized.
[8]
* Reflects holdings of U.S. Treasury Obligations Portfolio.
[9]
1 The expense table reflects the expenses of both the feeder Fund and the master Fund.
[10]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. Additional amounts may be voluntarily waived and/or reimbursed from time to time.
[11]
† Annualized.
[12]
* Reflects holdings of U.S. Treasury Obligations Portfolio.