Leases - Components of Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Short-term lease cost	$ 2	$ 1	$ 1
Variable lease cost	1,447	1,406	1,260
Amortization of finance lease liabilities	106	112	113
Interest on finance lease liabilities	15	19	22
Total net lease cost	1,842	1,823	1,701
Sublease income	17	41	78
Aircraft
Lessee, Lease, Description [Line Items]
Operating lease cost	188	204	216
Other
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 84	$ 81	$ 89