Operating Leases - Aircraft (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) aircraftEngine aircraft	Mar. 31, 2021 USD ($) aircraft aircraftEngine	Dec. 31, 2021 aircraft	May 31, 2021 aircraft
Lessee, Lease, Description [Line Items]
Gains recognized on sale-leaseback transactions | $	$ 7	$ 15
Number of aircraft terminated				6
Aircraft
Lessee, Lease, Description [Line Items]
Number of leases	112
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 month
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms	12 years
Aircraft Engine
Lessee, Lease, Description [Line Items]
Number of leases | aircraftEngine	21
Number of engines dependent on usage-based metrics | aircraftEngine	7
Aircraft Engine | Aircraft Sale Leaseback
Lessee, Lease, Description [Line Items]
Number of sale-leaseback transactions | aircraftEngine	0	1
Aircraft Engine | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 month
Aircraft Engine | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms	12 years
Aircraft and Aircraft Engines
Lessee, Lease, Description [Line Items]
Gains recognized on sale-leaseback transactions | $	$ 7	$ 15
A-320
Lessee, Lease, Description [Line Items]
Number of aircraft returned			2
A-320 | Aircraft | Aircraft Sale Leaseback
Lessee, Lease, Description [Line Items]
Number of sale-leaseback transactions	2	3
A-319
Lessee, Lease, Description [Line Items]
Number of aircraft terminated			4
A-319, To Be Returned Early
Lessee, Lease, Description [Line Items]
Charge included as a component of rent expense | $		$ 6
A-319, To Be Returned In Q2
Lessee, Lease, Description [Line Items]
Charge included as a component of rent expense | $		$ 4