Reconciliation of Adjusted EBITDA to Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Indefinite-lived Intangible Assets [Line Items]
Adjusted EBITDA	$ 781	$ 735	$ 838
Non-vehicle depreciation and amortization	256	259	253
Interest expense related to corporate debt, net	(188)	(188)	(203)
Early extinguishment of debt	19	3	27
Restructuring Charges	22	63	29
Transaction-related costs, net	20	23	21
Non-operational charges related to shareholder activist activity	9	0	0
Impairment	0	2	0
Charges for legal matter	0	(14)	26
Income before income taxes	267	211	279
Acquisition-related Costs [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Non-vehicle depreciation and amortization	$ 61	$ 58	$ 59