v3.26.1
S000052179 [Member] Expense Example, No Redemption - Western Asset SMASh Series TF Fund - Western Asset SMASh Series TF Fund
Feb. 28, 2026
USD ($)
Prospectus [Line Items]  
Expense Example, No Redemption, 1 Year $ 4
Expense Example, No Redemption, 3 Years 48
Expense Example, No Redemption, 5 Years 97
Expense Example, No Redemption, 10 Years $ 239