Basis of Presentation (Disaggregated Revenue in Basis of Presentation) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 2,371	$ 760	$ 3,743	$ 2,513
Avis
Disaggregation of Revenue [Line Items]
Revenues	1,204	402	1,921	1,387
Budget
Disaggregation of Revenue [Line Items]
Revenues	985	267	1,509	886
Other
Disaggregation of Revenue [Line Items]
Revenues	182	91	313	240
Americas
Disaggregation of Revenue [Line Items]
Revenues	1,974	565	3,054	1,822
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	281	159	484	516
Asia and Australasia
Disaggregation of Revenue [Line Items]
Revenues	$ 116	$ 36	$ 205	$ 175