Acquisitions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,083	$ 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	40
Business Acquisition Purchase Price Allocation Vehicles, Net	27
Payments to Acquire Businesses, Gross	64
Business Combination, Contingent Consideration, Liability	$ 3
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 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	$ 12