Segment Information (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Document Period End Date			Jun. 30, 2018
Revenues	$ 2,328	$ 2,238	$ 4,296	$ 4,077
Adjusted EBITDA	161	140	163	113
Non Vehicle Related Depreciation And Amortization	67	65	128	128
Restructuring and other related charges	4	38	10	45
Income (loss) before income taxes	38	11	(91)	(154)
Assets Under Vehicle Programs	14,726		14,726		$ 11,879
Total assets exclusive of assets under vehicle programs	6,193		6,193		5,820
Americas
Segment Reporting Information [Line Items]
Adjusted EBITDA	107	96	122	76
Assets Under Vehicle Programs	11,000		11,000		9,000
International [Member]
Segment Reporting Information [Line Items]
Revenues	738	673	1,358	1,198
Adjusted EBITDA	71	59	74	66
Assets Under Vehicle Programs	3,700		3,700		$ 2,900
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	$ (17)	$ (15)	$ (33)	$ (29)