Basis of Presentation Disaggregated Revenue in Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,920	$ 1,968
Americas [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,327	1,348
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	433	447
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Revenues	160	173
Avis [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,100	1,145
Budget [Member]
Disaggregation of Revenue [Line Items]
Revenues	651	642
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 169	$ 181