Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Fair Value of Stock Options Granted	$ 28.90	$ 28.47	$ 26.60
Total Intrinsic Value of Stock Options	$ 456	$ 177	$ 398
Unrecognized Compensation Cost Related to Nonvested Awards	$ 89
Employee Stock Purchase Plan ("ESPP") [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock were reserved for issuance	7,827
Compensation expense	$ 10	9
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Future Grants	21,162
Restricted Stock Units and Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs and PSUs, Vested, value	$ 413	$ 188	$ 216
Unrecognized Compensation Cost Related to Nonvested Awards	$ 304

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 number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

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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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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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