Basis of Presentation Disaggregated Revenue in Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Other related Revenue	$ 33		$ 63
Revenues	2,337	$ 2,328	4,257	$ 4,296
Americas [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,627	1,590	2,954	2,938
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	572	600	1,005	1,047
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Revenues	138	138	298	311
Avis [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,328	1,351	2,428	2,496
Budget [Member]
Disaggregation of Revenue [Line Items]
Revenues	816	777	1,467	1,419
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 193	$ 200	$ 362	$ 381