| Label | Element | Value |
|---|---|---|
| Franklin Ultra Short Bond ETF | Corporate Bonds & Notes [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 78.90% |
| Franklin Ultra Short Bond ETF | U.S. Government & Agency Obligations [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 0.80% |
| Franklin Ultra Short Bond ETF | Short-Term Investments [Member] | ||
| Holdings [Line Items] | oef_HoldingsLineItems | |
| Percent of Total Investments | oef_PctOfTotalInv | 20.30% |