Operating Leases - Aircraft (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) aircraft aircraftEngine	Jun. 30, 2021 USD ($) aircraft aircraftEngine	Jun. 30, 2022 USD ($) aircraft aircraftEngine	Jun. 30, 2021 USD ($) aircraft aircraftEngine	Dec. 31, 2021 aircraft	May 31, 2021 aircraft
Lessee, Lease, Description [Line Items]
Gains recognized on sale-leaseback transactions | $			$ 28	$ 36
Number of aircraft terminated						6
Aircraft
Lessee, Lease, Description [Line Items]
Number of leases	114		114
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 month		1 month
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms	12 years		12 years
Aircraft Engine
Lessee, Lease, Description [Line Items]
Number of leases | aircraftEngine	24		24
Number of engines dependent on usage-based metrics | aircraftEngine			8
Aircraft Engine | Aircraft Sale Leaseback
Lessee, Lease, Description [Line Items]
Number of sale-leaseback transactions | aircraftEngine	2	0	2	1
Aircraft Engine | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 month		1 month
Aircraft Engine | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms	12 years		12 years
Aircraft and Aircraft Engines
Lessee, Lease, Description [Line Items]
Gains recognized on sale-leaseback transactions | $	$ 21	$ 21	$ 28	$ 36
A320neo | Aircraft | Aircraft Sale Leaseback
Lessee, Lease, Description [Line Items]
Number of sale-leaseback transactions	3	5	5	8
A320ceo
Lessee, Lease, Description [Line Items]
Number of aircraft returned					2
A319
Lessee, Lease, Description [Line Items]
Number of aircraft terminated					4
A319, To Be Returned In Q2
Lessee, Lease, Description [Line Items]
Charge included as a component of rent expense | $		$ 5		$ 9