Share-Based Compensation - Summary of SAR's Outstanding (Detail) - $ / shares	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Granted	0	0	0
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of year	1,397,611	1,292,142	1,402,784
Shares Granted	627,971	332,159	195,560
Shares, Exercised	(160,946)	(179,702)	(267,077)
Shares, Forfeited	(115,215)	(45,441)	(38,738)
Shares, Expired	(8,635)	(1,547)	(387)
Shares, Outstanding at end of period	1,740,786	1,397,611	1,292,142
Shares, Exercisable at end of period	828,754	736,075	586,344
Weighted-average grant date fair value at beginning of year (in USD per share)	$ 56.15	$ 56.78	$ 42.20	$ 36.36
Weighted-average exercise price, Granted (in USD per share)	52.13	107.31	74.59
Weighted-average exercise price, Exercised (in USD per share)	35.37	40.71	34.03
Weighted-average exercise price, Forfeited (in USD per share)	65.74	75.26	50.57
Weighted-average exercise price, Expired (in USD per share)	88.65	47.11	46.07
Weighted-average exercise price, Exercisable at end of year (in USD per share)	$ 45.14	$ 35.90	$ 33.03

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option 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)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

+ 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)(1)(iv)(4)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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.

+ 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)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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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 of the plan that expired.

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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 per share amount at which grantees can acquire shares of common stock by exercise of options.

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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