The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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

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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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised, Number of Shares	(114,252)	(77,308)	(628,076)	(143,523)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			52,860
Granted, Number of Units			5,940
Stock Awards exercised/vested, Number of Shares			(2,499)
Ending Balance, Number of Shares/Units	56,301		56,301
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 75.47
Granted Weighted-Average Grant-Date Fair Value			117.90
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			92.03
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 79.21		$ 79.21
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			470,359
Forfeited/expired, Number of Shares/Units			(18,226)
Ending Balance, Number of Shares/Units	452,133		452,133
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 86.24
Forfeited/Expired, Weighted-Average Price			88.68
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 86.14		$ 86.14
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares			1,739,559
Stock options exercised, Number of Shares			(590,446)
Ending Balance, Number of Shares	1,149,113		1,149,113
Beginning Balance, Weighted-Average Exercise Price			$ 66.11
Stock options exercised, Weighted-Average Exercise Price			62.13
Ending Balance, Weighted-Average Exercise Price	$ 68.15		$ 68.15
Maximum [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares/Units			201,257
Stock Awards exercised/vested, Number of Shares			(35,131)
Forfeited/expired, Number of Shares/Units			(1,115)
Ending Balance, Number of Shares/Units	165,011		165,011
Beginning Balance, Weighted-Average Grant-Date Fair Value			$ 77.18
Stock Award Exercised/Vested, Weighted Average Grant Date Fair Value			92.27
Forfeited/Expired, Weighted-Average Price			92.27
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 73.86		$ 73.86