Summary of Segments Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 5,402	$ 9,172	$ 9,124
Vehicle depreciation and lease charges, net	1,368	2,063	2,179
Vehicle interest, net	(318)	(344)	(314)
Adjusted EBITDA	(175)	788	781
Non-vehicle depreciation and amortization	286	263	256
Assets exclusive of assets under vehicle programs	8,365	9,311	6,370
Assets under vehicle programs	9,173	13,815	12,779
Capital expenditures (excluding vehicles)	94	250	231
International
Segment Reporting Information [Line Items]
Revenues	1,437	2,820	2,938
Vehicle depreciation and lease charges, net	400	601	611
Vehicle interest, net	(44)	(60)	(62)
Adjusted EBITDA	(202)	203	287
Non-vehicle depreciation and amortization	91	94	104
Assets exclusive of assets under vehicle programs	2,754	2,995	2,495
Assets under vehicle programs	2,018	3,307	3,109
Capital expenditures (excluding vehicles)	29	62	76
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	0
Vehicle depreciation and lease charges, net	0
Vehicle interest, net	0
Adjusted EBITDA	(45)	(67)	(64)
Non-vehicle depreciation and amortization	10	8
Assets exclusive of assets under vehicle programs	101	90	93
Assets under vehicle programs	0
Capital expenditures (excluding vehicles)	0	26	21
Americas
Segment Reporting Information [Line Items]
Revenues	3,965	6,352	6,186
Vehicle depreciation and lease charges, net	968	1,462	1,568
Vehicle interest, net	(274)	(284)	(252)
Adjusted EBITDA	72	652	558
Non-vehicle depreciation and amortization	185	161	152
Assets exclusive of assets under vehicle programs	5,510	6,226	3,782
Assets under vehicle programs	7,155	10,508	9,670
Capital expenditures (excluding vehicles)	65	162	134
Acquisition-related Costs [Member]
Segment Reporting Information [Line Items]
Non-vehicle depreciation and amortization	$ 66	$ 56	$ 61