S000052179 [Member] Average Annual Total Returns |
12 Months Ended | 60 Months Ended | 108 Months Ended |
|---|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2024 |
Dec. 31, 2024 |
|
| Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 1.05% | 0.99% | 2.14% |
| Western Asset SMASh Series TF Fund | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 2.23% | 1.58% | 2.64% |
| Performance Inception Date | Dec. 23, 2015 | ||
| Western Asset SMASh Series TF Fund | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 2.22% | 1.58% | 2.29% |
| Western Asset SMASh Series TF Fund | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.06% | 1.92% | 2.36% |