| Label | Element | Value |
|---|---|---|
| Risk Return Abstract | rr_RiskReturnAbstract | |
| Registrant Name | dei_EntityRegistrantName | First Trust Exchange-Traded Fund III |
| Prospectus Date | rr_ProspectusDate | Dec. 02, 2024 |
| Document Creation Date | dei_DocumentCreationDate | Nov. 27, 2024 |