Share-Based Payments - Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period, shares \| shares	103,791
Granted, shares \| shares	1,181
Exercised, shares \| shares	(15,964)
Forfeited, shares \| shares	(55)
Expired, shares \| shares	(353)
Outstanding, end of period, shares \| shares	88,600
Vested and expected to vest, end of period, shares \| shares	88,469
Exercisable, end of period, shares \| shares	85,372
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period, weighted-average exercise price per share (in dollars per share) \| $ / shares	$ 27.69
Granted, weighted-average exercise price per share (in dollars per share) \| $ / shares	43.35
Exercised, weighted-average exercise price per share (in dollars per share) \| $ / shares	24.84
Forfeited, weighted-average exercise price per share (in dollars per share) \| $ / shares	37.67
Expired, weighted-average exercise price per share (in dollars per share) \| $ / shares	31.12
Outstanding, end of period, weighted-average exercise price per share (in dollars per share) \| $ / shares	28.39
Vested and expected to vest, end of period, weighted-average exercise price per share (in dollars per share) \| $ / shares	28.37
Exercisable, end of period, weighted-average exercise price per share (in dollars per share) \| $ / shares	$ 28.04
Outstanding, end of period, weighted-average remaining contractual term	3 years 7 months 6 days
Vested and expected to vest, end of period, weighted-average remaining contractual term	3 years 7 months 6 days
Exercisable, end of period, weighted-average remaining contractual term	3 years 4 months 24 days
Outstanding, end of period, aggregate intrinsic value \| $	$ 960
Vested and expected to vest, end of period, aggregate intrinsic value \| $	960
Exercisable, end of period, aggregate intrinsic value \| $	$ 951

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest exercisable or convertible options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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