Basis of Presentation Disaggregated Revenue in Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Other related Revenue	$ 30	$ 40	$ 84	$ 103
Revenues	1,534	2,753	4,047	7,010
Corporate Interest Expense [Member]
Disaggregation of Revenue [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	3	0	4	2
Americas [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,114	1,868	2,936	4,822
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	363	742	879	1,747
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Revenues	57	143	232	441
Avis [Member]
Disaggregation of Revenue [Line Items]
Revenues	843	1,580	2,230	4,008
Budget [Member]
Disaggregation of Revenue [Line Items]
Revenues	539	950	1,425	2,417
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 152	$ 223	$ 392	$ 585