Summary of Option Activities (Detail) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Options, Number of shares, beginning balance	8,133,176
Granted, Number of Shares	2,589,966
Exercised, Number of Shares	(1,534,741)
Expired, Number of Shares	(551,750)
Cancelled, Number of Shares	(397,685)
Outstanding Options, Number of shares, ending balance	8,238,966
Outstanding options vested and exercisable, Number of Shares	2,522,906	2,551,267	3,724,179
Outstanding Options, Average Option Price, beginning balance	$ 124.52
Granted, Average Option Price	70.36
Exercised, Average Option Price	118.99
Expired, Average Option Price	117.30
Cancelled, Average Option Price	114.79
Outstanding Options, Average Option Price, ending balance	109.47
Outstanding options vested and exercisable, Average Option Price	$ 124.62	$ 119.86	$ 106.77

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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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Weighted average price of options that were either forfeited or expired.

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

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

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

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