Leases - Lessee Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Lease charges		$ 156	$ 195	$ 255	$ 195
Minimum annual guaranteed rent in excess of concession fees, net	$ (2)	2	60
Property
Lessee, Lease, Description [Line Items]
Operating lease expense		561	575	722
Variable lease expense		433	152	274
Sublease income		(6)	(6)	(8)
Total property lease expense		988	721	988
Total vehicle lease expense		988	721	988
Buses and support vehicles
Lessee, Lease, Description [Line Items]
Total property lease expense		197	231	301
Amortization of ROU assets		37	33	42
Interest on lease liabilities		4	3	4
Total vehicle lease expense		$ 197	$ 231	$ 301