Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(428,599)	(752,075)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	53,008
Granted, Number of Units	6,576
Stock Awards Vested and Expected to Vest, Exercisable, Number	(10,674)
Ending Balance, Number of Shares	48,910
Beginning Balance, Director Deferred, Weighted-Average Grant-Date Fair Value	$ 64.87
Granted, Directors Deferred, Weighted-Average Grant-Date Fair Value	109.58
Ending Balance, Director Deferred, Weighted-Average Grant-Date Fair Value	71.14
Stock Award Vested, Weighted Average Grant Date Fair Value	$ 63.68
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	312,656
Stock Awards Vested and Expected to Vest, Exercisable, Number	(2,470)
Forfeited/expired, Number of Shares	(4,424)
Ending Balance, Number of Shares	305,762
Stock Award Vested, Weighted Average Grant Date Fair Value	$ 78.92
Beginning Balance, Weighted-Average Grant-Date Fair Value	81.71
Ending Balance, Weighted-Average Grant-Date Fair Value	81.65
Forfeited/expired, Weighted-Average Exercise Price	$ 87.24
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	2,917,142
Stock options exercised, Number of Shares	(415,455)
Forfeited/expired, Number of Shares	(43,875)
Ending Balance, Number of Shares	2,457,812
Beginning Balance, Weighted-Average Exercise Price	$ 63.34
Stock options exercised, Weighted-Average Exercise Price	61.25
Forfeited/expired, Weighted-Average Exercise Price	70.19
Ending Balance, Weighted-Average Exercise Price	$ 63.57
Maximum [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	80,103
Ending Balance, Number of Shares	80,103
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 79.91
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 79.91

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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 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 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 that were terminated.

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Weighted average grant-date fair value of options vested.

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

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