Stock-Based Employee Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to stock-based compensation plan	$ 85	$ 89	$ 84
Total income tax benefit related to stock-based compensation plan	30	31	29
Unrecognized compensation cost related to nonvested awards	78
Weighted average period of years over which unrecognized compensation cost will be reflected in operating results	1 year 8 months 12 days
Maximum number of shares in respect to which stock-based awards may be granted under the plan most recently approved by shareholders	7,400,000
Shares available for grant	8,200,000
Performance period in which performance unit awards are based	3 years
Stock option expiration period	10 years
Weighted average fair value per stock option granted	$ 15.48	$ 14.95	$ 11.95
Total intrinsic value of stock options exercised	2	16	40
Cash received from the exercise of stock options	3	10	47
Tax benefit realized with respect to the exercise of stock options	1	5	13
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share of the restricted stock units and performance units granted	$ 86.67	$ 83.75	$ 68.64
Total fair value of the restricted stock units and performance units vested	66	72	74
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share of the restricted stock units and performance units granted	$ 76.32	$ 98.46	$ 63.38
Total fair value of the restricted stock units and performance units vested	$ 17	$ 64	$ 70

The number of years in the performance period related to the performance unit awards.

No definition available.

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The expiration period of stock options.

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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.

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Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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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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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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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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