Summary of Significant Accounting Policies - Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 11,789	$ 12,008	$ 11,994
Avis
Disaggregation of Revenue [Line Items]
Revenues	6,775	6,779	6,519
Budget
Disaggregation of Revenue [Line Items]
Revenues	4,271	4,478	4,701
Other
Disaggregation of Revenue [Line Items]
Revenues	743	751	774
Americas
Disaggregation of Revenue [Line Items]
Revenues	9,111	9,347	9,474
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	2,045	2,014	1,927
Asia and Australasia
Disaggregation of Revenue [Line Items]
Revenues	$ 633	$ 647	$ 593