Reconciliation of Adjusted EBITDA to Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Indefinite-lived Intangible Assets [Line Items]
Adjusted EBITDA	$ 788	$ 781	$ 735
Non-vehicle depreciation and amortization	263	256	259
Interest expense related to corporate debt, net	(178)	(188)	(188)
Early extinguishment of debt	12	19	3
Restructuring Charges	80	22	63
Transaction-related costs, net	10	20	23
Non-operational charges related to shareholder activist activity	2	9	0
Impairment	0	0	2
Charges for legal matter	0	0	(14)
Income before income taxes	287	267	211
Acquisition-related Costs [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Non-vehicle depreciation and amortization	$ 56	$ 61	$ 58