Guarantor And Non-Guarantor Consolidating Condensed Financial Statements (Consolidating Condensed Statements Of Comprehensive Income) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Revenues	$ 2,328	$ 2,238	$ 4,296	$ 4,077
Expenses
Operating	1,175	1,108	2,267	2,157
Vehicle depreciation and lease charges, net	591	597	1,106	1,101
Selling, general and administrative	321	293	617	555
Vehicle interest, net	80	73	152	137
Non-vehicle related depreciation and amortization	67	65	128	128
Interest expense	49	48	95	97
Intercompany interest expense (income)	0	0	0	0
Early extinguishment of debt	0	0	5	3
Restructuring and other related charges	4	38	10	45
Transaction-related costs, net	3	5	7	8
Total expenses	2,290	2,227	4,387	4,231
Income before income taxes	38	11	(91)	(154)
Provision for (benefit from) income taxes	(12)	(8)	30	50
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net income (loss)	26	3	(61)	(104)
Comprehensive income (loss)	24	(51)	103	28
Eliminations [Member]
Revenues
Revenues	(657)	(663)	(1,232)	(1,248)
Expenses
Operating	0	0	0	0
Vehicle depreciation and lease charges, net	(596)	(609)	(1,121)	(1,144)
Selling, general and administrative	0	0	0	0
Vehicle interest, net	(61)	(54)	(111)	(104)
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	0
Restructuring and other related charges	0	0	0	0
Transaction-related costs, net	0	0	0	0
Total expenses	(657)	(663)	(1,232)	(1,248)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in earnings (loss) of subsidiaries	(283)	(341)	(367)	(349)
Net income (loss)	(283)	(341)	(367)	(349)
Comprehensive income (loss)	128	490	222	578
Parent Company [Member]
Revenues
Revenues	0	0	0	0
Expenses
Operating	1	1	2	2
Vehicle depreciation and lease charges, net	0	0	0	0
Selling, general and administrative	10	10	28	20
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)	(6)	(6)
Early extinguishment of debt		0	0	0
Restructuring and other related charges	0	0	0	0
Transaction-related costs, net	0	0	0	0
Total expenses	8	8	24	16
Income before income taxes	(8)	(8)	(24)	(16)
Provision for (benefit from) income taxes	5	2	11	4
Equity in earnings (loss) of subsidiaries	29	9	(48)	(92)
Net income (loss)	26	3	(61)	(104)
Comprehensive income (loss)	24	(51)	103	28
Subsidiaries [Member]
Revenues
Revenues	0	0	0	0
Expenses
Operating	(3)	9	1	13
Vehicle depreciation and lease charges, net	0	0	0	0
Selling, general and administrative	3	2	6	4
Vehicle interest, net	0	0	0	0
Non-vehicle related depreciation and amortization	1	1	1	1
Interest expense	39	83	78	129
Intercompany interest expense (income)	(31)	5	(9)	6
Early extinguishment of debt		1	5	4
Restructuring and other related charges	0	2	0	2
Transaction-related costs, net	1	0	1	0
Total expenses	10	103	83	159
Income before income taxes	(10)	(103)	(83)	(159)
Provision for (benefit from) income taxes	3	39	22	62
Equity in earnings (loss) of subsidiaries	36	73	13	5
Net income (loss)	29	9	(48)	(92)
Comprehensive income (loss)	21	(58)	90	16
Guarantor Subsidiaries [Member]
Revenues
Revenues	1,395	1,371	2,579	2,524
Expenses
Operating	677	644	1,298	1,284
Vehicle depreciation and lease charges, net	605	614	1,141	1,160
Selling, general and administrative	176	158	331	311
Vehicle interest, net	61	52	113	97
Non-vehicle related depreciation and amortization	36	40	72	80
Interest expense	1	0	2	1
Intercompany interest expense (income)	5	5	11	11
Early extinguishment of debt		0	0	0
Restructuring and other related charges	1	33	4	39
Transaction-related costs, net	1	0	1	0
Total expenses	1,563	1,546	2,973	2,983
Income before income taxes	(168)	(175)	(394)	(459)
Provision for (benefit from) income taxes	(14)	(11)	5	28
Equity in earnings (loss) of subsidiaries	218	259	402	436
Net income (loss)	36	73	13	5
Comprehensive income (loss)	16	(123)	37	(82)
Non-Guarantor Subsidiaries [Member]
Revenues
Revenues	1,590	1,530	2,949	2,801
Expenses
Operating	500	454	966	858
Vehicle depreciation and lease charges, net	582	592	1,086	1,085
Selling, general and administrative	132	123	252	220
Vehicle interest, net	80	75	150	144
Non-vehicle related depreciation and amortization	30	24	55	47
Interest expense	9	(35)	15	(33)
Intercompany interest expense (income)	29	(7)	4	(11)
Early extinguishment of debt		(1)	0	(1)
Restructuring and other related charges	3	3	6	4
Transaction-related costs, net	1	5	5	8
Total expenses	1,366	1,233	2,539	2,321
Income before income taxes	224	297	410	480
Provision for (benefit from) income taxes	(6)	(38)	(8)	(44)
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net income (loss)	218	259	402	436
Comprehensive income (loss)	$ (165)	$ (309)	$ (349)	$ (512)