Consolidated Statements Of Operations - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenues	$ 2,050	$ 2,778	$ 2,328	$ 1,968	$ 2,019	$ 2,752	$ 2,238	$ 1,839	$ 9,124	$ 8,848	$ 8,659
Expenses
Operating									4,639	4,472	4,382
Vehicle depreciation and lease charges, net									2,179	2,221	2,047
Selling, general and administrative									1,220	1,120	1,134
Vehicle interest, net									314	286	284
Non-vehicle related depreciation and amortization									256	259	253
Interest expense related to corporate debt, net:
Interest expense									188	188	203
Early extinguishment of debt									19	3	27
Restructuring and other related charges									22	63	29
Transaction-related costs, net									20	23	21
Impairment									0	2	0
Total expenses									8,857	8,637	8,380
Income before income taxes									267	211	279
Provision for (benefit from) income taxes									102	(150)	116
Net income									$ 165	$ 361	$ 163
Earnings per share
Basic	$ 0.16	$ 2.71	$ 0.33	$ (1.08)	$ 2.70	$ 2.96	$ 0.04	$ (1.25)	$ 2.08	$ 4.32	$ 1.78
Diluted	$ 0.16	$ 2.68	$ 0.32	$ (1.08)	$ 2.65	$ 2.91	$ 0.04	$ (1.25)	$ 2.06	$ 4.25	$ 1.75