Consolidating Condensed Statements of Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		$ 0	$ 0
Vehicle rental	$ 6,219	6,081	6,026
Other	2,629	2,578	2,476
Net revenues	8,848	8,659	8,502
Operating	4,472	4,382	4,284
Vehicle depreciation and lease charges, net	2,221	2,047	1,933
Selling, general and administrative	1,120	1,134	1,093
Vehicle interest, net	286	284	289
Non-vehicle related depreciation and amortization	259	253	218
Interest expense	188	203	194
Intercompany interest expense (income)	0	0	0
Early extinguishment of debt	3	27	23
Impairment	23	21	68
Restructuring Charges	63	29	18
Impairment of Intangible Assets (Excluding Goodwill)	2
Total expenses	8,637	8,380	8,120
Income before income taxes	211	279	382
Provision for (benefit from) income taxes	(150)	116	69
Equity in earnings (loss) of subsidiaries	0	0	0
Net income	361	163	313
Total comprehensive income	491	156	188
Payments for (Proceeds from) Other Investing Activities	5	1	3
Net Cash Provided by (Used in) Investing Activities	(2,204)	(2,182)	(2,685)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	45	(6)	(50)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	181	3	(36)
Program cash	283	225
Restricted Cash and Cash Equivalents	7	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	901	720	717	$ 753
Parent Company
Condensed Financial Statements, Captions [Line Items]
Vehicle rental	0	0	0
Other	0	0	0
Net revenues	0	0	0
Operating	3	4	2
Vehicle depreciation and lease charges, net	0	0	0
Selling, general and administrative	39	38	32
Vehicle interest, net	0	0	0
Non-vehicle related depreciation and amortization	0	0	0
Interest expense	0	0	0
Intercompany interest expense (income)	(12)	(13)	(12)
Early extinguishment of debt	0	0	0
Impairment	0	0	0
Restructuring Charges	0	0	0
Impairment of Intangible Assets (Excluding Goodwill)	0
Total expenses	30	29	22
Income before income taxes	(30)	(29)	(22)
Provision for (benefit from) income taxes	(5)	(11)	(9)
Equity in earnings (loss) of subsidiaries	386	181	326
Net income	361	163	313
Total comprehensive income	491	156	188
Payments for (Proceeds from) Other Investing Activities	100	118	334
Net Cash Provided by (Used in) Investing Activities	100	118	334
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	0	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	1	(1)	2
Program cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	4	3	4	2
Subsidiary Issuers
Condensed Financial Statements, Captions [Line Items]
Vehicle rental	0	0	0
Other	0	0	0
Net revenues	0	0	0
Operating	20	18	17
Vehicle depreciation and lease charges, net	0	0	1
Selling, general and administrative	8	18	15
Vehicle interest, net	0	0	0
Non-vehicle related depreciation and amortization	1	2	1
Interest expense	157	141	159
Intercompany interest expense (income)	95	(7)	(11)
Early extinguishment of debt	4	10	23
Impairment	1	2	22
Restructuring Charges	7	0	0
Impairment of Intangible Assets (Excluding Goodwill)	0
Total expenses	293	184	227
Income before income taxes	(293)	(184)	(227)
Provision for (benefit from) income taxes	267	(70)	(178)
Equity in earnings (loss) of subsidiaries	946	295	375
Net income	386	181	326
Total comprehensive income	515	173	203
Payments for (Proceeds from) Other Investing Activities	110	(1)	(127)
Net Cash Provided by (Used in) Investing Activities	106	(4)	(166)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	0	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	2	(58)	(140)
Program cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	14	12	70	210
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Vehicle rental	4,108	4,134	4,124
Other	1,204	1,209	1,181
Net revenues	5,312	5,343	5,305
Operating	2,598	2,622	2,587
Vehicle depreciation and lease charges, net	2,226	1,993	1,819
Selling, general and administrative	619	631	619
Vehicle interest, net	199	198	204
Non-vehicle related depreciation and amortization	160	155	133
Interest expense	1	3	(5)
Intercompany interest expense (income)	23	23	16
Early extinguishment of debt	0	0	0
Impairment	3	1	6
Restructuring Charges	44	9	6
Impairment of Intangible Assets (Excluding Goodwill)	2
Total expenses	5,875	5,635	5,385
Income before income taxes	(563)	(292)	(80)
Provision for (benefit from) income taxes	(527)	123	170
Equity in earnings (loss) of subsidiaries	982	710	625
Net income	946	295	375
Total comprehensive income	1,073	283	253
Payments for (Proceeds from) Other Investing Activities	110	0	1
Net Cash Provided by (Used in) Investing Activities	24	(65)	(203)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	0	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	0	0	0
Program cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0	0	0	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		0	0
Vehicle rental	2,111	1,947	1,902
Other	3,820	3,563	3,335
Net revenues	5,931	5,510	5,237
Operating	1,851	1,738	1,678
Vehicle depreciation and lease charges, net	2,183	2,045	1,936
Selling, general and administrative	454	447	427
Vehicle interest, net	294	289	302
Non-vehicle related depreciation and amortization	98	96	84
Interest expense	30	59	40
Intercompany interest expense (income)	(106)	(3)	7
Early extinguishment of debt	(1)	17	0
Impairment	19	18	40
Restructuring Charges	12	20	12
Impairment of Intangible Assets (Excluding Goodwill)	0
Total expenses	4,834	4,726	4,526
Income before income taxes	1,097	784	711
Provision for (benefit from) income taxes	115	74	86
Equity in earnings (loss) of subsidiaries	0	0	0
Net income	982	710	625
Total comprehensive income	1,103	712	504
Payments for (Proceeds from) Other Investing Activities	5	2	5
Net Cash Provided by (Used in) Investing Activities	(2,378)	(2,401)	(2,566)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	45	(6)	(50)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	178	62	102
Program cash	283	225
Restricted Cash and Cash Equivalents	7	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	883	705	643	541
Eliminations
Condensed Financial Statements, Captions [Line Items]
Vehicle rental	0	0	0
Other	(2,395)	(2,194)	(2,040)
Net revenues	(2,395)	(2,194)	(2,040)
Operating	0	0	0
Vehicle depreciation and lease charges, net	(2,188)	(1,991)	(1,823)
Selling, general and administrative	0	0	0
Vehicle interest, net	(207)	(203)	(217)
Non-vehicle related depreciation and amortization	0	0	0
Interest expense	0	0	0
Intercompany interest expense (income)	0	0	0
Early extinguishment of debt	0	0	0
Impairment	0	0	0
Restructuring Charges	0	0	0
Impairment of Intangible Assets (Excluding Goodwill)	0
Total expenses	(2,395)	(2,194)	(2,040)
Income before income taxes	0	0	0
Provision for (benefit from) income taxes	0	0	0
Equity in earnings (loss) of subsidiaries	(2,314)	(1,186)	(1,326)
Net income	(2,314)	(1,186)	(1,326)
Total comprehensive income	(2,691)	(1,168)	(960)
Payments for (Proceeds from) Other Investing Activities	(320)	(118)	(210)
Net Cash Provided by (Used in) Investing Activities	(56)	170	(84)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash	0	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	0	0	0
Program cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 0	0	0	0
Restatement Adjustment [Member]
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		(31)	148
Payments for (Proceeds from) Other Investing Activities		(2)	(3)
Net Cash Provided by (Used in) Investing Activities		(33)	145
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash		(2)	(9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(35)	136
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		230	265	129
Restatement Adjustment [Member] | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		(31)	148
Payments for (Proceeds from) Other Investing Activities		(2)	(3)
Net Cash Provided by (Used in) Investing Activities		(33)	145
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash		(2)	(9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(35)	136
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		230	265	129
Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		31	(148)
Payments for (Proceeds from) Other Investing Activities		3	6
Net Cash Provided by (Used in) Investing Activities		(2,149)	(2,830)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash		(4)	(41)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		38	(172)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		490	452	624
Scenario, Previously Reported [Member] | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Decrease Increase In Program Cash		31	(148)
Payments for (Proceeds from) Other Investing Activities		4	8
Net Cash Provided by (Used in) Investing Activities		(2,368)	(2,711)
Effect of changes in exchange rates on cash and cash equivalents, program and restricted cash		(4)	(41)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		97	(34)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 475	$ 378	$ 412