Segment Information (Summary Of Segments Information) (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]
Assets Under Vehicle Programs	$ 14,019		$ 14,019		$ 11,578
Document Fiscal Year Focus			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
Interest expense	48	56	97	106
Early extinguishment of debt	0	(10)	(3)	(10)
Early extinguishment of debt	0	10	3	10
Transaction-related costs, net	5	5	8	9
Charges for legal matter	(27)	0	(14)	0
Restructuring and other related charges	38	5	45	20
Income before income taxes	11	63	(154)	(23)
International
Segment Reporting Information [Line Items]
Assets Under Vehicle Programs	10,600		10,600		9,200
Revenues	1,565	1,593	2,879	2,957
Adjusted EBITDA	96	163	76	226
International
Segment Reporting Information [Line Items]
Assets Under Vehicle Programs	3,300		3,300		$ 2,400
Revenues	673	650	1,198	1,167
Adjusted EBITDA	59	57	66	58
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	$ (15)	$ (16)	$ (29)	$ (36)