Financial Derivative Instruments - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | 12 Months Ended |
|---|---|---|---|
Dec. 31, 2026 |
Sep. 30, 2026 |
Dec. 31, 2027 |
|
| 5.250% Notes | Unsecured Debt | |||
| Derivative [Line Items] | |||
| Face amount of debt | $ 750 | ||
| Interest rate stated in the debt agreement (as a percent) | 5.25% | ||
| Fuel derivative contracts | |||
| Derivative [Line Items] | |||
| Other comprehensive loss in AOCI related to termination of fuel hedging contracts | $ 50 | ||
| Fuel derivative contracts | Forecast | |||
| Derivative [Line Items] | |||
| Other comprehensive loss in AOCI related to termination of fuel hedging contracts | $ 29 | $ 21 |
| X | ||||||||||
- Definition Face (par) amount of debt instrument at time of issuance. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Contractual interest rate for funds borrowed, under the debt agreement. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|