Guarantor And Non-Guarantor Consolidating Condensed Financial Statements (Consolidating Condensed Statements Of Comprehensive Income) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Revenues	$ 2,778	$ 2,752	$ 7,074	$ 6,829
Expenses
Operating	1,294	1,256	3,561	3,413
Vehicle depreciation and lease charges, net	587	616	1,693	1,717
Selling, general and administrative	336	320	953	875
Vehicle interest, net	85	78	237	215
Non-vehicle related depreciation and amortization	62	66	190	194
Interest expense	44	45	139	142
Intercompany interest expense (income)	0	0	0	0
Early extinguishment of debt	0	0	5	3
Restructuring and other related charges	4	7	14	52
Transaction-related costs, net	11	0	18	8
Total expenses	2,423	2,388	6,810	6,619
Income before income taxes	355	364	264	210
Provision for (benefit from) income taxes	(142)	(119)	(112)	(69)
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net income (loss)	213	245	152	141
Comprehensive income (loss)	(207)	(279)	(104)	(251)
Eliminations [Member]
Revenues
Revenues	(560)	(611)	(1,792)	(1,859)
Expenses
Operating	0	0	0	0
Vehicle depreciation and lease charges, net	(504)	(557)	(1,625)	(1,701)
Selling, general and administrative	0	0	0	0
Vehicle interest, net	(56)	(54)	(167)	(158)
Non-vehicle related depreciation and amortization	0	0	0	0
Interest expense	0	0	0	0
Intercompany interest expense (income)	0	0	0	0
Early extinguishment of debt			0	0
Restructuring and other related charges	0	0	0	0
Transaction-related costs, net	0		0	0
Total expenses	(560)	(611)	(1,792)	(1,859)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in earnings (loss) of subsidiaries	(812)	(895)	(1,179)	(1,244)
Net income (loss)	(812)	(895)	(1,179)	(1,244)
Comprehensive income (loss)	794	993	1,016	1,571
Parent Company [Member]
Revenues
Revenues	0	0	0	0
Expenses
Operating	0	0	2	2
Vehicle depreciation and lease charges, net	0	0	0	0
Selling, general and administrative	10	9	38	29
Vehicle interest, net	0	0	0	0
Non-vehicle related depreciation and amortization	0	0	0	0
Interest expense	0	0	0	0
Intercompany interest expense (income)	(3)	(3)	(9)	(9)
Early extinguishment of debt			0	0
Restructuring and other related charges	0	0	0	0
Transaction-related costs, net	0		0	0
Total expenses	7	6	31	22
Income before income taxes	(7)	(6)	(31)	(22)
Provision for (benefit from) income taxes	2	6	13	10
Equity in earnings (loss) of subsidiaries	218	245	170	153
Net income (loss)	213	245	152	141
Comprehensive income (loss)	(207)	(279)	(104)	(251)
Subsidiaries [Member]
Revenues
Revenues	0	0	0	0
Expenses
Operating	3	5	4	18
Vehicle depreciation and lease charges, net	0	0	0	0
Selling, general and administrative	3	2	9	6
Vehicle interest, net	0	0	0	0
Non-vehicle related depreciation and amortization	0	0	1	1
Interest expense	37	38	115	118
Intercompany interest expense (income)	1	25	(8)	80
Early extinguishment of debt			5	4
Restructuring and other related charges	0	5	0	7
Transaction-related costs, net	0		1	0
Total expenses	44	75	127	234
Income before income taxes	(44)	(75)	(127)	(234)
Provision for (benefit from) income taxes	12	30	34	92
Equity in earnings (loss) of subsidiaries	250	290	263	295
Net income (loss)	218	245	170	153
Comprehensive income (loss)	(212)	(278)	(122)	(262)
Guarantor Subsidiaries [Member]
Revenues
Revenues	1,592	1,569	4,171	4,093
Expenses
Operating	737	710	2,035	1,994
Vehicle depreciation and lease charges, net	540	568	1,681	1,728
Selling, general and administrative	182	174	513	485
Vehicle interest, net	59	53	172	150
Non-vehicle related depreciation and amortization	36	41	108	121
Interest expense	0	2	2	3
Intercompany interest expense (income)	9	6	20	17
Early extinguishment of debt			0	0
Restructuring and other related charges	2	(2)	6	37
Transaction-related costs, net	2		3	0
Total expenses	1,567	1,552	4,540	4,535
Income before income taxes	25	17	(369)	(442)
Provision for (benefit from) income taxes	(119)	(87)	(114)	(59)
Equity in earnings (loss) of subsidiaries	344	360	746	796
Net income (loss)	250	290	263	295
Comprehensive income (loss)	(244)	(323)	(207)	(405)
Non-Guarantor Subsidiaries [Member]
Revenues
Revenues	1,746	1,794	4,695	4,595
Expenses
Operating	554	541	1,520	1,399
Vehicle depreciation and lease charges, net	551	605	1,637	1,690
Selling, general and administrative	141	135	393	355
Vehicle interest, net	82	79	232	223
Non-vehicle related depreciation and amortization	26	25	81	72
Interest expense	7	5	22	21
Intercompany interest expense (income)	(7)	(28)	(3)	(88)
Early extinguishment of debt			0	(1)
Restructuring and other related charges	2	4	8	8
Transaction-related costs, net	9		14	8
Total expenses	1,365	1,366	3,904	3,687
Income before income taxes	381	428	791	908
Provision for (benefit from) income taxes	(37)	(68)	(45)	(112)
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net income (loss)	344	360	746	796
Comprehensive income (loss)	$ (338)	$ (392)	$ (687)	$ (904)