Segment Information (Summary Of Segments Information) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 3,001	$ 1,534	$ 6,744	$ 4,047
Adjusted EBITDA	1,057	220	1,728	(249)
Less:
Non-vehicle related depreciation and amortization	69	74	204	214
Interest expense	47	64	167	163
Early extinguishment of debt	7	2	136	9
Restructuring and other related charges	5	17	47	89
Transaction-related costs, net	1	0	3	3
Non-operational charges related to shareholder activist activity			0	4
COVID-19 charges	(6)	10	12	90
Unprecedented personal-injury and other legal matters, net	5	0	(6)	0
Net income (loss)	929	53	1,165	(821)
Minimum annual guaranteed rent in excess of concession fees, net	(4)	11	12	41
Vehicles damaged in overflow parking lots, net of insurance proceeds	(3)	(19)	(7)	14
Incremental cleaning supplies to sanitize vehicles and facilities, and over flow parking for idle vehicles	0	18	0	35
Other charges	1	0	7	0
COVID-19 charges	(6)	10	12	90
Operating expense
Less:
Non-vehicle related depreciation and amortization			5
COVID-19 charges	(6)	8	11	87
COVID-19 charges	(6)	8	11	87
Vehicle Depreciation and Lease Charges
Less:
COVID-19 charges	0	1	0	1
COVID-19 charges	0	1	0	1
Selling, General and Administrative Expenses
Less:
COVID-19 charges	0	1	1	2
COVID-19 charges	0	1	1	2
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDA	(23)	(8)	(52)	(34)
Americas | Geographical
Segment Reporting Information [Line Items]
Revenues	2,403	1,114	5,457	2,936
Adjusted EBITDA	952	222	1,694	(41)
International | Geographical
Segment Reporting Information [Line Items]
Revenues	598	420	1,287	1,111
Adjusted EBITDA	$ 128	$ 6	$ 86	$ (174)