Acquisitions - Additional Information (Detail) € in Millions, $ in Millions	1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2016 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 EUR (€)
Business Acquisition [Line Items]
Commitments and contingencies (Note 14)
Transaction-related costs, net					20	23	$ 21
Goodwill		$ 1,007			1,092	1,073	1,007
Income (Loss) from Equity Method Investments					0	0	$ 0
Equity Method Investments					0	0
2018 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred					$ 38
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					2 years
2018 Avis and Budget Licensees [Member] | Licensing Agreements [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					$ 42
Turiscar Group [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Oct. 01, 2018
Business Combination, Consideration Transferred					$ 25
Business Combination, Contingent Consideration, Liability | €								€ 4
Payments to Acquire Businesses, Gross					$ 26
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					11 years
Goodwill					$ 12
Turiscar Group [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					10
Turiscar Group [Member] | Trademarks
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					$ 2
Morini S.p.A. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Jul. 01, 2018
Business Combination, Consideration Transferred					$ 40
Business Combination, Contingent Consideration, Liability					6			€ 7
Payments to Acquire Businesses, Gross					$ 32
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					6 years
Goodwill					$ 42
Morini S.p.A. [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					6
Morini S.p.A. [Member] | Trademarks
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					3
Morini S.p.A. [Member] | Licensing Agreements [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired					$ 2
2017 Avis and Budget Licensees [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other						$ 9
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						3 years
Transaction-related costs, net						$ 2
2017 Avis and Budget Licensees [Member] | Licensing Agreements [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired						12
ACL Hire Limited [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2017
Business Combination, Consideration Transferred						5
Commitments and contingencies (Note 14)						2
Goodwill						6
France Cars [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Dec. 01, 2016
Business Combination, Consideration Transferred		$ 45
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life							8 years
Goodwill		$ 22					$ 22
France Cars [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired							$ 9
France Cars [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired						$ 6
Greece [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Mar. 01, 2018
Equity Method Investment, Ownership Percentage			20.00%	20.00%	40.00%			40.00%
Payments to Acquire Equity Method Investments			$ 20	$ 19
Equity Method Investments					$ 8