Segment Information (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Document Period End Date			Jun. 30, 2017
Revenues	$ 2,238	$ 2,243	$ 4,077	$ 4,124
Adjusted EBITDA	140	204	113	248
Non Vehicle Related Depreciation And Amortization	65	65	128	126
Restructuring and other related charges	38	5	45	20
Income (loss) before income taxes	11	63	(154)	(23)
Assets Under Vehicle Programs	14,019		14,019		$ 11,578
Total assets exclusive of assets under vehicle programs	6,813		6,813		6,065
International
Segment Reporting Information [Line Items]
Revenues	673	650	1,198	1,167
Adjusted EBITDA	59	57	66	58
Assets Under Vehicle Programs	3,300		3,300		2,400
Total assets exclusive of assets under vehicle programs	2,600		2,600		2,000
International
Segment Reporting Information [Line Items]
Revenues	1,565	1,593	2,879	2,957
Adjusted EBITDA	96	163	76	226
Assets Under Vehicle Programs	10,600		10,600		$ 9,200
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	$ (15)	$ (16)	$ (29)	$ (36)