Basis of Presentation Disaggregated Revenue in Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Other related Revenue	$ 32	$ 30
Revenues	1,753	1,920
Americas [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,257	1,327
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	357	433
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Revenues	139	160
Avis [Member]
Disaggregation of Revenue [Line Items]
Revenues	985	1,100
Budget [Member]
Disaggregation of Revenue [Line Items]
Revenues	619	651
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 149	$ 169