Segment Information - Reconciliation of Adjusted EBITDA to Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Adjusted EBITDA		$ 2,411	$ (175)	$ 788
Less:
Non-vehicle depreciation and amortization		279	286	263
Interest expense related to corporate debt, net
Interest expense		218	231	178
Early extinguishment of debt		136	9	12
Covid-19 charges		(2)	122
Restructuring and other related charges		64	118	80
Unprecedented personal-injury and other legal matters, net		3	8	0
Non-operational charges related to shareholder activist activity		0	4	2
Transaction-related costs, net		5	3	10
Gain on sale of equity method investment in China		0	0	(44)
Income (loss) before income taxes		1,708	(956)	287
Minimum annual guaranteed rent in excess of concession fees, net	$ (2)	2	60
Vehicles damaged in overflow parking lots, net of insurance proceeds	(7)		14
Incremental cleaning supplies to sanitize vehicles and facilities, and over flow parking for idle vehicles	0		48
Other charges	7		0
Covid-19 charges		(2)	122
Operating Expense
Interest expense related to corporate debt, net
Covid-19 charges	(3)		116
Covid-19 charges	(3)		116
Operating Expense | Cloud Computing Costs
Less:
Non-vehicle depreciation and amortization		7
Vehicle Depreciation and Lease Charges
Interest expense related to corporate debt, net
Covid-19 charges	0		1
Covid-19 charges	0		1
Selling, General and Administrative Expenses
Interest expense related to corporate debt, net
Covid-19 charges	1		5
Covid-19 charges	$ 1		5
Acquisition-related Costs
Less:
Non-vehicle depreciation and amortization		$ 66	$ 66	$ 56