Basis of Presentation (Disaggregated Revenue in Basis of Presentation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 1,372	$ 1,753
Avis
Disaggregation of Revenue [Line Items]
Revenues	717	985
Budget
Disaggregation of Revenue [Line Items]
Revenues	524	619
Other
Disaggregation of Revenue [Line Items]
Revenues	131	149
Americas
Disaggregation of Revenue [Line Items]
Revenues	1,080	1,257
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	203	357
Asia and Australasia
Disaggregation of Revenue [Line Items]
Revenues	$ 89	$ 139