Segment Information (Narrative) (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]
Document Period End Date			Sep. 30, 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
Restructuring and other related charges	7	6	52	26
Income before income taxes	364	345	210	322
Assets Under Vehicle Programs	13,085		13,085		$ 11,578
Total assets exclusive of assets under vehicle programs	6,788		6,788		6,065
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]
Revenues	913	835	2,111	2,002
Adjusted EBITDA	194	179	260	237
Assets Under Vehicle Programs	3,500		3,500		2,400
Total assets exclusive of assets under vehicle programs	2,600		2,600		$ 2,000
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	$ (15)	$ (16)	$ (44)	$ (52)