Summary of Segments Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net revenues	$ 8,848	$ 8,659	$ 8,502
Vehicle depreciation and lease charges, net	2,221	2,047	1,933
Vehicle interest, net	(286)	(284)	(289)
Adjusted EBITDA	735	838	903
Non-vehicle depreciation and amortization	259	253	218
Assets exclusive of assets under vehicle programs	5,820	6,065	5,918
Assets under vehicle programs	11,879	11,578	11,716
Capital expenditures (excluding vehicles)	197	190	199
Americas
Segment Reporting Information [Line Items]
Net revenues	6,100	6,121	6,069
Vehicle depreciation and lease charges, net	1,671	1,559	1,478
Vehicle interest, net	(226)	(226)	(234)
Adjusted EBITDA	486	633	682
Non-vehicle depreciation and amortization	168	165	143
Assets exclusive of assets under vehicle programs	3,388	4,017	3,940
Assets under vehicle programs	9,017	9,210	9,440
Capital expenditures (excluding vehicles)	122	121	131
International
Segment Reporting Information [Line Items]
Net revenues	2,748	2,538	2,433
Vehicle depreciation and lease charges, net	550	488	455
Vehicle interest, net	(60)	(58)	(55)
Adjusted EBITDA	305	273	277
Non-vehicle depreciation and amortization	91	88	75
Assets exclusive of assets under vehicle programs	2,353	1,990	1,901
Assets under vehicle programs	2,862	2,368	2,276
Capital expenditures (excluding vehicles)	62	62	68
Corporate and Other
Segment Reporting Information [Line Items]
Adjusted EBITDA	(56)	(68)	(56)
Assets exclusive of assets under vehicle programs	79	58	77
Capital expenditures (excluding vehicles)	13	7
Acquisition-related Costs [Member]
Segment Reporting Information [Line Items]
Non-vehicle depreciation and amortization	$ 58	$ 59	$ 55