Consolidating Condensed Statements of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 2,629	$ 2,584	$ 2,579
Investing activities
Property and equipment additions	(190)	(199)	(182)
Proceeds received on asset sales	19	15	21
Net assets acquired (net of cash acquired)	(55)	(256)	(416)
intercompany loan receipts	0	0
Other, net	3	6	(11)
Net cash used in investing activities exclusive of vehicle programs	(223)	(434)	(588)
Vehicle programs:
Decrease in program cash	31	(148)	(10)
Investment In Vehicles	(12,461)	(11,928)	(11,875)
Proceeds received on disposition of vehicles	10,504	9,680	9,666
Net Cash Used In Investing Activities Of Vehicle Programs	(1,926)	(2,396)	(2,219)
Net cash used in investing activities	(2,149)	(2,830)	(2,807)
Financing activities
Proceeds from borrowings	894	377	871
Principal payments on borrowings	(847)	(301)	(762)
Proceeds from (Repayments of) Short-term Debt	4	(22)	5
Debt financing fees	(20)	(7)	(17)
Payments for Repurchase of Common Stock	(387)	(393)	(297)
Intercompany loan borrowings	0	0
Other, net	0	(7)	0
Net cash used in financing activities exclusive of vehicle programs	(356)	(353)	(200)
Vehicle programs:
Proceeds from borrowings	15,769	14,138	14,373
Principal payments on borrowings	(15,826)	(13,648)	(13,963)
Debt financing fees	(25)	(22)	(28)
Net cash provided by financing activities of vehicle programs	(82)	468	382
Net cash provided by (used in) financing activities	(438)	115	182
Effect of changes in exchange rates on cash and cash equivalents	(4)	(41)	(23)
Net increase (decrease) in cash and cash equivalents	38	(172)	(69)
Cash and cash equivalents, beginning of period	452	624	693
Cash and cash equivalents, end of period	490	452	624
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	268	60	0
Investing activities
Property and equipment additions	0	0	0
Proceeds received on asset sales	0	0	0
Net assets acquired (net of cash acquired)	0	0	0
intercompany loan receipts	0	0
Other, net	118	334	285
Net cash used in investing activities exclusive of vehicle programs	118	334	285
Vehicle programs:
Decrease in program cash	0	0	0
Investment In Vehicles	0	0	0
Proceeds received on disposition of vehicles	0	0	0
Net Cash Used In Investing Activities Of Vehicle Programs	0	0	0
Net cash used in investing activities	118	334	285
Financing activities
Proceeds from borrowings	0	0	0
Principal payments on borrowings	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Debt financing fees	0	0	0
Payments for Repurchase of Common Stock	(387)	(393)	(297)
Intercompany loan borrowings	0	0
Other, net	0	1	0
Net cash used in financing activities exclusive of vehicle programs	(387)	(392)	(297)
Vehicle programs:
Proceeds from borrowings	0	0	0
Principal payments on borrowings	0	0	0
Debt financing fees	0	0	0
Net cash provided by financing activities of vehicle programs	0	0	0
Net cash provided by (used in) financing activities	(387)	(392)	(297)
Effect of changes in exchange rates on cash and cash equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	(1)	2	(12)
Cash and cash equivalents, beginning of period	4	2	14
Cash and cash equivalents, end of period	3	4	2
Subsidiary Issuers
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(10)	249	469
Investing activities
Property and equipment additions	(32)	(26)	(20)
Proceeds received on asset sales	7	7	7
Net assets acquired (net of cash acquired)	0	(8)	0
intercompany loan receipts	0	(30)
Other, net	(1)	(127)	(9)
Net cash used in investing activities exclusive of vehicle programs	(26)	(184)	(22)
Vehicle programs:
Decrease in program cash	0	0	0
Investment In Vehicles	(9)	(1)	(9)
Proceeds received on disposition of vehicles	31	19	8
Net Cash Used In Investing Activities Of Vehicle Programs	22	18	(1)
Net cash used in investing activities	(4)	(166)	(23)
Financing activities
Proceeds from borrowings	557	375	575
Principal payments on borrowings	(525)	(256)	(756)
Proceeds from (Repayments of) Short-term Debt	0	0	0
Debt financing fees	(15)	(7)	(12)
Payments for Repurchase of Common Stock	0	0	0
Intercompany loan borrowings	316	0
Other, net	(385)	(335)	(285)
Net cash used in financing activities exclusive of vehicle programs	(52)	(223)	(478)
Vehicle programs:
Proceeds from borrowings	8	0	0
Principal payments on borrowings	0	0	0
Debt financing fees	0	0	0
Net cash provided by financing activities of vehicle programs	8	0	0
Net cash provided by (used in) financing activities	(44)	(223)	(478)
Effect of changes in exchange rates on cash and cash equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	(58)	(140)	(32)
Cash and cash equivalents, beginning of period	70	210	242
Cash and cash equivalents, end of period	12	70	210
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	80	146	340
Investing activities
Property and equipment additions	(89)	(98)	(84)
Proceeds received on asset sales	4	1	8
Net assets acquired (net of cash acquired)	(4)	(9)	(263)
intercompany loan receipts	28	(96)
Other, net	0	1	(2)
Net cash used in investing activities exclusive of vehicle programs	(61)	(201)	(341)
Vehicle programs:
Decrease in program cash	0	0	0
Investment In Vehicles	(4)	(2)	(90)
Proceeds received on disposition of vehicles	0	0	0
Net Cash Used In Investing Activities Of Vehicle Programs	(4)	(2)	(90)
Net cash used in investing activities	(65)	(203)	(431)
Financing activities
Proceeds from borrowings	0	0	0
Principal payments on borrowings	(5)	(4)	(5)
Proceeds from (Repayments of) Short-term Debt	0	0	0
Debt financing fees	0	0	0
Payments for Repurchase of Common Stock	0	0	0
Intercompany loan borrowings	0	0
Other, net	0	70	0
Net cash used in financing activities exclusive of vehicle programs	(5)	66	(5)
Vehicle programs:
Proceeds from borrowings	0	0	88
Principal payments on borrowings	(9)	(9)	(3)
Debt financing fees	(1)	0	(1)
Net cash provided by financing activities of vehicle programs	(10)	(9)	84
Net cash provided by (used in) financing activities	(15)	57	79
Effect of changes in exchange rates on cash and cash equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	0	(12)
Cash and cash equivalents, beginning of period	0	0	12
Cash and cash equivalents, end of period	0	0	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	2,633	2,204	1,840
Investing activities
Property and equipment additions	(69)	(75)	(78)
Proceeds received on asset sales	8	7	6
Net assets acquired (net of cash acquired)	(51)	(239)	(153)
intercompany loan receipts	(316)	0
Other, net	4	8	0
Net cash used in investing activities exclusive of vehicle programs	(424)	(299)	(225)
Vehicle programs:
Decrease in program cash	31	(148)	(10)
Investment In Vehicles	(12,448)	(11,925)	(11,776)
Proceeds received on disposition of vehicles	10,473	9,661	9,658
Net Cash Used In Investing Activities Of Vehicle Programs	(1,944)	(2,412)	(2,128)
Net cash used in investing activities	(2,368)	(2,711)	(2,353)
Financing activities
Proceeds from borrowings	337	2	296
Principal payments on borrowings	(317)	(41)	(1)
Proceeds from (Repayments of) Short-term Debt	4	(22)	5
Debt financing fees	(5)	0	(5)
Payments for Repurchase of Common Stock	0	0	0
Intercompany loan borrowings	(28)	126
Other, net	(75)	(28)	(70)
Net cash used in financing activities exclusive of vehicle programs	(84)	37	225
Vehicle programs:
Proceeds from borrowings	15,761	14,138	14,285
Principal payments on borrowings	(15,817)	(13,639)	(13,960)
Debt financing fees	(24)	(22)	(27)
Net cash provided by financing activities of vehicle programs	(80)	477	298
Net cash provided by (used in) financing activities	(164)	514	523
Effect of changes in exchange rates on cash and cash equivalents	(4)	(41)	(23)
Net increase (decrease) in cash and cash equivalents	97	(34)	(13)
Cash and cash equivalents, beginning of period	378	412	425
Cash and cash equivalents, end of period	475	378	412
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(342)	(75)	(70)
Investing activities
Property and equipment additions	0	0	0
Proceeds received on asset sales	0	0	0
Net assets acquired (net of cash acquired)	0	0	0
intercompany loan receipts	288	126
Other, net	(118)	(210)	(285)
Net cash used in investing activities exclusive of vehicle programs	170	(84)	(285)
Vehicle programs:
Decrease in program cash	0	0	0
Investment In Vehicles	0	0	0
Proceeds received on disposition of vehicles	0	0	0
Net Cash Used In Investing Activities Of Vehicle Programs	0	0	0
Net cash used in investing activities	170	(84)	(285)
Financing activities
Proceeds from borrowings	0	0	0
Principal payments on borrowings	0	0	0
Proceeds from (Repayments of) Short-term Debt	0	0	0
Debt financing fees	0	0	0
Payments for Repurchase of Common Stock	0	0	0
Intercompany loan borrowings	(288)	(126)
Other, net	460	285	355
Net cash used in financing activities exclusive of vehicle programs	172	159	355
Vehicle programs:
Proceeds from borrowings	0	0	0
Principal payments on borrowings	0	0	0
Debt financing fees	0	0	0
Net cash provided by financing activities of vehicle programs	0	0	0
Net cash provided by (used in) financing activities	172	159	355
Effect of changes in exchange rates on cash and cash equivalents	0	0	0
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of period	0	0	0
Cash and cash equivalents, end of period	$ 0	$ 0	$ 0