Operating Leases - Aircraft Rent Expense and Maintenance Obligations (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
|
| Lessee, Lease, Description [Line Items] | |||||
| Aircraft rent expense | $ 266 | $ 194 | $ 531 | $ 355 | |
| Supplemental rent expense (benefit) related to probable lease return condition obligations | 63 | $ 15 | 121 | $ 3 | |
| Leased aircraft return cost liability | $ 135 | 135 | $ 19 | ||
| Aircraft | |||||
| Lessee, Lease, Description [Line Items] | |||||
| Gain lease extension | $ 20 | ||||