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Financial Derivative Instruments - Premiums for Fuel Derivative Contracts (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2023
Jun. 30, 2022
Jun. 30, 2023
Jun. 30, 2022
Fuel derivative contracts | Designated as Hedging Instrument | Fuel and oil        
Derivative [Line Items]        
Premium expense recognized in income on derivatives $ 30 $ 26 $ 61 $ 53