Acquisitions (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,107	$ 1,092
2019 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Goodwill	21
2019 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other	32
Business Acquisition Purchase Price Allocation Vehicles, Net	$ 19
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years
Customer relationships [Member] | 2019 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 7
Licensing Agreements | 2019 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 4