Share-Based Compensation - Certain Information Regarding Company's Share-Based Compensation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense, Total	$ 10,515	$ 10,288	$ 17,386
Deferred tax benefits, Total	4,019	3,933	5,348
Realized tax benefits, Total	7,095	5,050	5,369
Excess tax benefits (shortfall)	5,793	(1,154)	5,310
Intrinsic value of options exercised	$ 15,256	1,894	14,734
Cash received for strike price and tax withholdings		$ 119	$ 519
Shares acquired through cashless exercise	491	325	611
Value of shares acquired through cashless exercise	$ 12,808	$ 6,238	$ 15,445
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense, Stock options	6,907	3,641	1,389
Deferred tax benefits, Total	2,640	1,392	532
Realized tax benefits, Total	5,831	724	5,369
Excess tax benefits (shortfall)	$ 5,548	$ 642	$ 5,310
Weighted average fair value per option or share, Stock option grants	$ 10.18	$ 6.01	$ 6.34
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense		$ 3,433	$ 15,997
Deferred tax benefits, Total		1,312	$ 4,816
Realized tax benefits, Total		4,326
Excess tax benefits (shortfall)		(1,796)
Weighted average fair value per option or share, Restricted stock grants/Performance share unit grants			$ 26.04
Fair value of restricted stock vested/performance share units vested		11,319	$ 17,505
Performance Share Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense	$ 3,608	3,214
Deferred tax benefits, Total	1,379	$ 1,229
Realized tax benefits, Total	1,264
Excess tax benefits (shortfall)	$ 245
Weighted average fair value per option or share, Restricted stock grants/Performance share unit grants	$ 27.20	$ 23.18
Fair value of restricted stock vested/performance share units vested	$ 3,307

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Amount of deferred income tax expense (benefit) and income tax credits.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
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- Definition

Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

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Cash received for strike price and tax withholdings.

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Value of shares acquired.

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