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).

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- Definition

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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- Definition

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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No definition available.

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- Definition

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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- Definition

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

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No definition available.

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- Definition

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
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- Definition

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

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- Definition

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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- Definition

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

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No definition available.

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- Definition

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

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No definition available.

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Weighted average grant-date fair value of options vested.

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No definition available.

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(53,035)	(110,489)	(153,900)	(428,599)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			48,910
Granted, Number of Units			7,592
Ending Balance, Number of Shares	56,502		56,502
Beginning Balance, Director Deferred, Weighted-Average Grant-Date Fair Value			$ 71.14
Ending Balance, Director Deferred, Weighted-Average Grant-Date Fair Value	$ 75.38		75.38
Granted Weighted-Average Grant-Date Fair Value			$ 102.70
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			383,797
Granted, Number of Units			1,957
Stock Awards exercised/vested, Number of shares	(17,800)		(17,800)
Forfeited/expired, Number of Shares			(3,877)
Ending Balance, Number of Shares	364,077		364,077
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 85.59
Granted Weighted-Average Grant-Date Fair Value			91.96
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			65.11
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 86.58		86.58
Forfeited/expired, Weighted-Average Exercise Price			$ 90.10
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			2,352,008
Stock options exercised, Number of Shares			(136,100)
Forfeited/expired, Number of Shares			(6,875)
Ending Balance, Number of Shares	2,209,033		2,209,033
Beginning Balance, Weighted-Average Exercise Price			$ 63.55
Stock options exercised, Weighted-Average Exercise Price			57.61
Forfeited/expired, Weighted-Average Exercise Price			65.11
Ending Balance, Weighted-Average Exercise Price	$ 63.91		$ 63.91
Maximum [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			125,809
Ending Balance, Number of Shares	125,809		125,809
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 82.55
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 82.55		$ 82.55