Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Fair Value of Stock Options Granted	$ 35.98	$ 38.21	$ 28.90
Total Intrinsic Value of Stock Options	$ 328	$ 153	$ 456
Unrecognized Compensation Cost Related to Nonvested Awards	$ 53
Employee Stock Purchase Plan ("ESPP") [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock were reserved for issuance	5,865,000
Compensation expense	$ 13	12	10
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Future Grants	20,274,000
Restricted Stock Units and Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs and PSUs, Vested, value	$ 349	$ 346	$ 413
Unrecognized Compensation Cost Related to Nonvested Awards	$ 330

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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