Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Currency translation adjustment	$ 51	$ 166	$ 193	$ 159
Net carrying value of software developed	140us-gaap_CapitalizedComputerSoftwareNet	108us-gaap_CapitalizedComputerSoftwareNet
Vehicle interest income	10car_VehicleInterestIncome	9car_VehicleInterestIncome	8car_VehicleInterestIncome
Advertising expense	112us-gaap_AdvertisingExpense	116us-gaap_AdvertisingExpense	127us-gaap_AdvertisingExpense
Investments in joint ventures	46
Aggregate realized gain from the sale of investments	7		2
Retained risks of liability to third parties	397car_RetainedRisksOfLiabilities	416car_RetainedRisksOfLiabilities
Workers compensation liabilities	67	59
Gain or loss of currency transactions	$ 9	$ 11	$ 17

Retained Risks Of Liabilities

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- Definition

Vehicle Interest Income

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- Definition

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

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- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

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-Paragraph 1

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- Definition

The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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-Publisher FASB

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This item represents the gain (loss) realized during the period from the sale of investments accounted for under the cost method of accounting and any losses recognized thereon for impairments of other than a temporary nature.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

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-Article 5

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Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

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- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

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- Definition

Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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