Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Based Compensation Percentage In Annual Base Salary, Min	50.00%
Deferred Compensation Arrangement with Individual, Shares Issued	20,000	33,000	53,000
Maximum number of shares reserved for grant of awards	18,500,000
Shares available for grant under the plan	5,400,000
Aggregate Intrinsic Value - Exercised	$ 6	$ 23	$ 11
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	95.00%
Allocated Share-based Compensation Expense	34	24	16
Allocated Share-based Compensation Expense, Net of Tax	21	14	10
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	56
Employee Service Share Based Compensation Incremental Tax Benefit To Be Realized From Exercise Of Stock Awards	$ 22

Employee service share based compensation incremental tax benefit to be realized from exercise of stock awards.

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- Definition

Share based compensation percentage in annual base salary, min.

+ References

No definition available.

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- Definition

Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

+ References

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-Publisher FASB

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

No definition available.

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- Definition

Number of shares issued pursuant to the terms of a deferred compensation arrangement.

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- Definition

Discount rate from fair value on purchase date that participants pay for shares.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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