Guarantor And Non-Guarantor Consolidating Condensed Financial Statements (Consolidating Condensed Statements Of Cash Flows) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	$ 447	$ 472
Property and equipment additions	(42)	(40)
Proceeds received on asset sales	2	3
Payments to Acquire Restricted Investments	0	(1)
Proceeds from (Repayments of) Related Party Debt	0	0
Other, net	0	0
Net cash used in investing activities exclusive of vehicle programs	(40)	(38)
Decrease (increase) in program cash	87	198
Investment in vehicles	(3,944)	(4,140)
Proceeds received on disposition of vehicles	2,958	2,776
Repayments of Related Party Debt	(33)	0
Net cash used in investing activities of vehicle programs	(932)	(1,166)
Net cash used in investing activities	(972)	(1,204)
Proceeds from long-term borrowings	590	350
Principal payments on borrowings	(143)	(5)
Net change in short-term borrowings	0	1
Intercompany loan borrowings	0	0
Repurchases of common stock	(61)	(95)
Debt financing fees	(7)	(5)
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	379	246
Proceeds from borrowings	5,812	4,694
Principal payments on borrowings	(5,236)	(3,796)
Debt financing fees	(5)	(6)
Net cash provided by financing activities of vehicle programs	571	892
Net cash provided by financing activities	950	1,138
Effect of changes in exchange rates on cash and cash equivalents	8	18
Net increase in cash and cash equivalents	433	424
Cash and cash equivalents, beginning of period	490	452
Cash and cash equivalents, end of period	923	876
Parent [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	7	9
Property and equipment additions	0	0
Proceeds received on asset sales	0	0
Payments to Acquire Restricted Investments		0
Proceeds from (Repayments of) Related Party Debt	0	0
Other, net	53	86
Net cash used in investing activities exclusive of vehicle programs	53	86
Decrease (increase) in program cash	0	0
Investment in vehicles	0	0
Proceeds received on disposition of vehicles	0	0
Repayments of Related Party Debt	0
Net cash used in investing activities of vehicle programs	0	0
Net cash used in investing activities	53	86
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	0	0
Net change in short-term borrowings		0
Intercompany loan borrowings	0	0
Repurchases of common stock	(61)	(95)
Debt financing fees	0	0
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	(61)	(95)
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	(61)	(95)
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	(1)	0
Cash and cash equivalents, beginning of period	3	4
Cash and cash equivalents, end of period	2	4
Subsidiary Issuers [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	(130)	17
Property and equipment additions	(8)	(4)
Proceeds received on asset sales	1	2
Payments to Acquire Restricted Investments		0
Proceeds from (Repayments of) Related Party Debt	0	0
Other, net	0	0
Net cash used in investing activities exclusive of vehicle programs	(7)	(2)
Decrease (increase) in program cash	0	0
Investment in vehicles	0	0
Proceeds received on disposition of vehicles	8	11
Repayments of Related Party Debt	0
Net cash used in investing activities of vehicle programs	8	11
Net cash used in investing activities	1	9
Proceeds from long-term borrowings	325	350
Principal payments on borrowings	(142)	(4)
Net change in short-term borrowings		0
Intercompany loan borrowings	270	0
Repurchases of common stock	0	0
Debt financing fees	(3)	(5)
Other, net	(53)	(86)
Net cash provided by financing activities exclusive of vehicle programs	397	255
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	397	255
Effect of changes in exchange rates on cash and cash equivalents	0	0
Net increase in cash and cash equivalents	268	281
Cash and cash equivalents, beginning of period	12	70
Cash and cash equivalents, end of period	280	351
Guarantor Subsidiaries [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	24	(2)
Property and equipment additions	(19)	(21)
Proceeds received on asset sales	0	0
Payments to Acquire Restricted Investments		0
Proceeds from (Repayments of) Related Party Debt	0	27
Other, net	0	0
Net cash used in investing activities exclusive of vehicle programs	(19)	6
Decrease (increase) in program cash	0	0
Investment in vehicles	(1)	(1)
Proceeds received on disposition of vehicles	0	0
Repayments of Related Party Debt	0
Net cash used in investing activities of vehicle programs	(1)	(1)
Net cash used in investing activities	(20)	5
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	(1)	(1)
Net change in short-term borrowings		0
Intercompany loan borrowings	0	0
Repurchases of common stock	0	0
Debt financing fees	0	0
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	(1)	(1)
Proceeds from borrowings	0	0
Principal payments on borrowings	(3)	(2)
Debt financing fees	0	0
Net cash provided by financing activities of vehicle programs	(3)	(2)
Net cash provided by financing activities	(4)	(3)
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	546	448
Property and equipment additions	(15)	(15)
Proceeds received on asset sales	1	1
Payments to Acquire Restricted Investments		(1)
Proceeds from (Repayments of) Related Party Debt	(270)	0
Other, net	0	0
Net cash used in investing activities exclusive of vehicle programs	(284)	(15)
Decrease (increase) in program cash	87	198
Investment in vehicles	(3,943)	(4,139)
Proceeds received on disposition of vehicles	2,950	2,765
Repayments of Related Party Debt	(33)
Net cash used in investing activities of vehicle programs	(939)	(1,176)
Net cash used in investing activities	(1,223)	(1,191)
Proceeds from long-term borrowings	265	0
Principal payments on borrowings	0	0
Net change in short-term borrowings		1
Intercompany loan borrowings	0	(27)
Repurchases of common stock	0	0
Debt financing fees	(4)	0
Other, net	0	0
Net cash provided by financing activities exclusive of vehicle programs	261	(26)
Proceeds from borrowings	5,812	4,694
Principal payments on borrowings	(5,233)	(3,794)
Debt financing fees	(5)	(6)
Net cash provided by financing activities of vehicle programs	574	894
Net cash provided by financing activities	835	868
Effect of changes in exchange rates on cash and cash equivalents	8	18
Net increase in cash and cash equivalents	166	143
Cash and cash equivalents, beginning of period	475	378
Cash and cash equivalents, end of period	641	521
Eliminations [Member]
Supplemental Guarantor Financial Information [Line Items]
Net cash provided by (used in) operating activities	0	0
Property and equipment additions	0	0
Proceeds received on asset sales	0	0
Payments to Acquire Restricted Investments		0
Proceeds from (Repayments of) Related Party Debt	270	(27)
Other, net	(53)	(86)
Net cash used in investing activities exclusive of vehicle programs	217	(113)
Decrease (increase) in program cash	0	0
Investment in vehicles	0	0
Proceeds received on disposition of vehicles	0	0
Repayments of Related Party Debt	0
Net cash used in investing activities of vehicle programs	0	0
Net cash used in investing activities	217	(113)
Proceeds from long-term borrowings	0	0
Principal payments on borrowings	0	0
Net change in short-term borrowings		0
Intercompany loan borrowings	(270)	27
Repurchases of common stock	0	0
Debt financing fees	0	0
Other, net	53	86
Net cash provided by financing activities exclusive of vehicle programs	(217)	113
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	(217)	113
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