Reconciliation of Adjusted EBITDA to Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Indefinite-lived Intangible Assets [Line Items]
Adjusted EBITDA	$ 735	$ 838	$ 903
Non-vehicle depreciation and amortization	259	253	218
Interest expense related to corporate debt, net	(188)	(203)	(194)
Early extinguishment of debt	3	27	23
Restructuring Charges	63	29	18
Impairment	23	21	68
Asset Impairment Charges	2	0	0
Charges for legal matter	(14)	26	0
Income before income taxes	211	279	382
Acquisition-related Costs [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Non-vehicle depreciation and amortization	$ 58	$ 59	$ 55