Stock-Based Compensation - Summary of Activity in Corporation's Active Stock Plans (Detail) - $ / shares	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Shares Available for Grant	1,589,727
Forfeited/expired, Shares Available for Grant	26,775
Ending Balance, Shares Available for Grant	1,616,502
Stock options exercised, Number of Shares	(1,875)	(14,350)
Director deferred stock units outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	45,443
Ending Balance, Number of Shares	45,443
Beginning Balance, Director Deferred, Weighted-Average Grant-Date Fair Value	$ 61.35
Ending Balance, Director Deferred, Weighted-Average Grant-Date Fair Value	$ 61.35
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	173,180
Ending Balance, Number of Shares	173,180
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 66.05
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 66.05
Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	5,612,240
Stock options exercised, Number of Shares	(1,875)
Forfeited/expired, Number of Shares	(26,775)
Ending Balance, Number of Shares	5,583,590
Beginning Balance, Weighted-Average Exercise Price	$ 60.30
Stock options exercised, Weighted-Average Exercise Price	51.21
Forfeited/expired, Weighted-Average Exercise Price	70.55
Ending Balance, Weighted-Average Exercise Price	$ 60.26

Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures Shares Available for Grant

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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.

+ References

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)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (c)(1)(iv)(3)
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- Definition

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

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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

As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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