Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Fair Value of Stock Options Granted	$ 28.47	$ 26.60	$ 26.10
Total Intrinsic Value of Stock Options	$ 177
Unrecognized Compensation Cost Related to Nonvested Awards	$ 74
Employee Stock Purchase Plan ("ESPP") [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock were reserved for issuance	8,681,600
Compensation expense	$ 9	$ 8
Restricted Stock Units and Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based awards granted	2,788,000	2,628,000	3,105,000
Number of share-based awards vested	2,254,000	3,112,000	2,881,000
Unrecognized Compensation Cost Related to Nonvested Awards	$ 257
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based awards granted	2,787,700	2,628,500
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based awards granted	1,879,100	1,601,300
Number of share-based awards vested	11,284,400
Shares Available for Future Grants	22,755,600

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
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Aggregate number of common shares reserved for future issuance.

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-Publisher FASB
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- Definition

Unrecognized cost of unvested share-based compensation awards.

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- Definition

The number of grants made 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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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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