Schedule of Information about All Outstanding Options (Detail) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number, Options Outstanding	8,133,176	9,674,791	9,639,949
Weighted average exercise price, Options Outstanding	$ 124.52	$ 115.39	$ 112.40
Aggregate intrinsic value, Options Outstanding	$ 154,591,751
Weighted average remaining contractual life, Options Outstanding	2 years 8 months 12 days	2 years 7 months 6 days	2 years 10 months 24 days
Number, Options Exercisable	2,551,267	3,724,179	2,869,346
Weighted Average Exercise Price, Options Exercisable	$ 119.86	$ 106.77	$ 100.51
Aggregate intrinsic value, Options Exercisable	$ 60,222,515
Weighted average remaining contractual life, Options Exercisable	1 year 4 months 24 days

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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, 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 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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