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, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense, Total	$ 12,786	$ 10,515	$ 10,288
Deferred tax benefits, Total	2,830	4,019	3,933
Realized tax benefits, Total	8,877	7,095	5,050
Excess tax benefits (shortfall)	5,427	5,793	(1,154)
Intrinsic value of options exercised	32,217	15,256	1,894
Cash received for strike price and tax withholdings	$ 120	$ 0	$ 119
Shares acquired through cashless exercise	1,361	491	325
Value of shares acquired through cashless exercise	$ 49,199	$ 12,808	$ 6,238
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense, Stock options	7,579	6,907	3,641
Deferred tax benefits, Total	1,877	2,640	1,392
Realized tax benefits, Total	7,957	5,831	724
Excess tax benefits (shortfall)	$ 5,330	$ 5,548	$ 642
Weighted average fair value per option or share, Stock option grants (in dollars per share)	$ 11.74	$ 10.18	$ 6.01
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 609	$ 0	$ 3,433
Deferred tax benefits, Total	8	0	1,312
Realized tax benefits, Total	0	0	4,326
Excess tax benefits (shortfall)	$ 0	$ 0	$ (1,796)
Granted, weighted average grant date fair value (in dollars per share)	$ 33.64	$ 0	$ 0
Fair value vested/performance share units vested	$ 632	$ 0	$ 11,319
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	4,598	3,608	3,214
Deferred tax benefits, Total	945	1,379	1,229
Realized tax benefits, Total	920	1,264	0
Excess tax benefits (shortfall)	$ 97	$ 245	$ 0
Granted, weighted average grant date fair value (in dollars per share)	$ 32.51	$ 27.20	$ 23.18
Fair value vested/performance share units vested	$ 3,726	$ 3,307	$ 0

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.

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

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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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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The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

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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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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.

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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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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.

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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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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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