Basis of Presentation Disaggregated Revenue in Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Other related Revenue	$ 40		$ 103
Revenues	2,753	$ 2,778	7,010	$ 7,074
Americas [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,868	1,844	4,822	4,782
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	742	784	1,747	1,830
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Revenues	143	150	441	462
Avis [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,580	1,599	4,008	4,095
Budget [Member]
Disaggregation of Revenue [Line Items]
Revenues	950	953	2,417	2,372
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 223	$ 226	$ 585	$ 607