Guarantor And Non-Guarantor Consolidating Condensed Financial Statements (Consolidating Condensed Statements Of Cash Flows) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	$ 2,101	$ 2,038
Property and equipment additions	(125)	(126)
Proceeds received on asset sales	10	8
Payments to Acquire Restricted Investments	(4)	(225)
Proceeds from (Repayments of) Related Party Debt	0	0
Other, net	4	3
Net cash used in investing activities exclusive of vehicle programs	(115)	(340)
Decrease (increase) in program cash	138	(71)
Investment in vehicles	(10,151)	(9,762)
Proceeds received on disposition of vehicles	7,373	6,756
Net cash used in investing activities of vehicle programs	(2,640)	(3,077)
Net cash used in investing activities	(2,755)	(3,417)
Proceeds from long-term borrowings	896	377
Principal payments on borrowings	(527)	(290)
Net change in short-term borrowings	1	(23)
Intercompany loan borrowings	0	0
Repurchases of common stock	(289)	(270)
Debt financing fees	(15)	(7)
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	66	(213)
Proceeds from borrowings	11,879	11,532
Principal payments on borrowings	(10,752)	(9,933)
Debt financing fees	(20)	(17)
Net cash provided by financing activities of vehicle programs	1,107	1,582
Net cash provided by financing activities	1,173	1,369
Effect of changes in exchange rates on cash and cash equivalents	14	(29)
Net increase in cash and cash equivalents	533	(39)
Cash and cash equivalents, beginning of period	452	624
Cash and cash equivalents, end of period	985	585
Parent [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	195	60
Property and equipment additions	0	0
Proceeds received on asset sales	0	0
Payments to Acquire Restricted Investments	0	0
Proceeds from (Repayments of) Related Party Debt	0	0
Other, net	93	212
Net cash used in investing activities exclusive of vehicle programs	93	212
Decrease (increase) in program cash	0	0
Investment in vehicles	0	0
Proceeds received on disposition of vehicles	0	0
Net cash used in investing activities of vehicle programs	0	0
Net cash used in investing activities	93	212
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	0	0
Net change in short-term borrowings	0	0
Intercompany loan borrowings	0	0
Repurchases of common stock	(289)	(270)
Debt financing fees	0	0
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	(289)	(270)
Proceeds from borrowings	0	0
Principal payments on borrowings	0	0
Debt financing fees	0	0
Net cash provided by financing activities of vehicle programs	0	0
Net cash provided by financing activities	(289)	(270)
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(1)	2
Cash and cash equivalents, beginning of period	4	2
Cash and cash equivalents, end of period	3	4
Subsidiary Issuers [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	372	270
Property and equipment additions	(15)	(17)
Proceeds received on asset sales	5	4
Payments to Acquire Restricted Investments	0	(8)
Proceeds from (Repayments of) Related Party Debt	0	(30)
Other, net	(1)	(107)
Net cash used in investing activities exclusive of vehicle programs	(11)	(158)
Decrease (increase) in program cash	0	0
Investment in vehicles	(3)	(1)
Proceeds received on disposition of vehicles	25	15
Net cash used in investing activities of vehicle programs	22	14
Net cash used in investing activities	11	(144)
Proceeds from long-term borrowings	557	375
Principal payments on borrowings	(523)	(253)
Net change in short-term borrowings	0	0
Intercompany loan borrowings	337	0
Repurchases of common stock	0	0
Debt financing fees	(10)	(7)
Other, net	(288)	(212)
Net cash provided by financing activities exclusive of vehicle programs	73	(97)
Proceeds from borrowings	0	0
Principal payments on borrowings	0	0
Debt financing fees	0	0
Net cash provided by financing activities of vehicle programs	0	0
Net cash provided by financing activities	73	(97)
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	456	29
Cash and cash equivalents, beginning of period	70	210
Cash and cash equivalents, end of period	526	239
Guarantor Subsidiaries [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	50	104
Property and equipment additions	(63)	(64)
Proceeds received on asset sales	1	0
Payments to Acquire Restricted Investments	(1)	(3)
Proceeds from (Repayments of) Related Party Debt	28	(94)
Other, net	0	1
Net cash used in investing activities exclusive of vehicle programs	(35)	(160)
Decrease (increase) in program cash	0	0
Investment in vehicles	(4)	(3)
Proceeds received on disposition of vehicles		0
Net cash used in investing activities of vehicle programs	(4)	(3)
Net cash used in investing activities	(39)	(163)
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	(3)	(4)
Net change in short-term borrowings	0	0
Intercompany loan borrowings	0	0
Repurchases of common stock	0	0
Debt financing fees	0	0
Other, net	0	70
Net cash provided by financing activities exclusive of vehicle programs	(3)	66
Proceeds from borrowings	0	0
Principal payments on borrowings	(7)	(7)
Debt financing fees	(1)	0
Net cash provided by financing activities of vehicle programs	(8)	(7)
Net cash provided by financing activities	(11)	59
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Non-Guarantor Subsidiaries [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	1,679	1,604
Property and equipment additions	(47)	(45)
Proceeds received on asset sales	4	4
Payments to Acquire Restricted Investments	(3)	(214)
Proceeds from (Repayments of) Related Party Debt	(337)	0
Other, net	5	3
Net cash used in investing activities exclusive of vehicle programs	(378)	(252)
Decrease (increase) in program cash	138	(71)
Investment in vehicles	(10,144)	(9,758)
Proceeds received on disposition of vehicles	7,348	6,741
Net cash used in investing activities of vehicle programs	(2,658)	(3,088)
Net cash used in investing activities	(3,036)	(3,340)
Proceeds from long-term borrowings	339	2
Principal payments on borrowings	(1)	(33)
Net change in short-term borrowings	1	(23)
Intercompany loan borrowings	(28)	124
Repurchases of common stock	0	0
Debt financing fees	(5)	0
Other, net	0	36
Net cash provided by financing activities exclusive of vehicle programs	306	106
Proceeds from borrowings	11,879	11,532
Principal payments on borrowings	(10,745)	(9,926)
Debt financing fees	(19)	(17)
Net cash provided by financing activities of vehicle programs	1,115	1,589
Net cash provided by financing activities	1,421	1,695
Effect of changes in exchange rates on cash and cash equivalents	14	(29)
Net increase in cash and cash equivalents	78	(70)
Cash and cash equivalents, beginning of period	378	412
Cash and cash equivalents, end of period	456	342
Eliminations [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	(195)	0
Property and equipment additions	0	0
Proceeds received on asset sales	0	0
Payments to Acquire Restricted Investments	0	0
Proceeds from (Repayments of) Related Party Debt	309	124
Other, net	(93)	(106)
Net cash used in investing activities exclusive of vehicle programs	216	18
Decrease (increase) in program cash	0	0
Investment in vehicles	0	0
Proceeds received on disposition of vehicles	0	0
Net cash used in investing activities of vehicle programs	0	0
Net cash used in investing activities	216	18
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	0	0
Net change in short-term borrowings	0	0
Intercompany loan borrowings	(309)	(124)
Repurchases of common stock	0	0
Debt financing fees	0	0
Other, net	288	106
Net cash provided by financing activities exclusive of vehicle programs	(21)	(18)
Proceeds from borrowings	0	0
Principal payments on borrowings	0	0
Debt financing fees		0
Net cash provided by financing activities of vehicle programs	0	0
Net cash provided by financing activities	(21)	(18)
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 0