| Label | Element | Value |
|---|---|---|
| Franklin Short Duration U.S. Government ETF | U.S. Government & Agency Obligations [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 41.30% |
| Franklin Short Duration U.S. Government ETF | Mortgage-Backed Securities [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 31.30% |
| Franklin Short Duration U.S. Government ETF | Collateralized Mortgage Obligations [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 18.80% |
| Franklin Short Duration U.S. Government ETF | Short-Term Investments [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 8.60% |