Segment Information (Summary Of Segments Information) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets Under Vehicle Programs	$ 13,085		$ 13,085		$ 11,578
Document Fiscal Year Focus			2017
Revenues	2,752	$ 2,656	$ 6,829	$ 6,780
Adjusted EBITDA	482	469	595	717
Non-vehicle related depreciation and amortization	66	63	194	189
Interest expense	45	51	142	157
Early extinguishment of debt	0	0	(3)	(10)
Early extinguishment of debt			3	10
Transaction-related costs, net	0	4	8	13
Charges for legal matter			(14)	0
Restructuring and other related charges	7	6	52	26
Income before income taxes	364	345	210	322
Americas [Member]
Segment Reporting Information [Line Items]
Revenues	1,839	1,821	4,718	4,778
Adjusted EBITDA	303	306	379	532
International
Segment Reporting Information [Line Items]
Assets Under Vehicle Programs	3,500		3,500		$ 2,400
Revenues	913	835	2,111	2,002
Adjusted EBITDA	194	179	260	237
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	$ (15)	$ (16)	$ (44)	$ (52)