Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Property
Operating Leases
Within 1 year	$ 577
Between 1 and 2 years	466
Between 2 and 3 years	335
Between 3 and 4 years	255
Between 4 and 5 years	202
Thereafter	1,056
Total lease payments	2,891
Less: Imputed interest	(485)
Total	2,406	$ 2,592
Buses and support vehicles
Operating Leases
Within 1 year	51
Between 1 and 2 years	13
Between 2 and 3 years	1
Between 3 and 4 years	0
Between 4 and 5 years	0
Thereafter	0
Total lease payments	65
Less: Imputed interest	(1)
Total	64	113
Finance Leases
Within 1 year	126
Between 1 and 2 years	5
Between 2 and 3 years	95
Between 3 and 4 years	16
Between 4 and 5 years	0
Thereafter	0
Total lease payments	242
Less: Imputed interest	0
Total	$ 242	$ 226