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Stock appreciation rights liabilities noncurrent.

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Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

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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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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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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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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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Price of a single share of a number of saleable stocks of a company.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stock-based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock authorized for share based payment awards under 2011 Plan	2,600,000
Shares available for grant under the 2011 plan	665,374
Compensation expenses	$ 6,837,000	$ 7,151,000	$ 12,618,000
Decrease increase in market value of company common stock, per share	$ 74.00	$ 78.97	$ 81.48
Decrease in market value of common stock	$ 4.97	$ 2.51
Income tax benefit recognized in the income statement for share-based compensation arrangements	$ 1,849,000	$ 2,980,124	$ 4,761,000
Proceeds from stock option exercises	$ 4,163,000	$ 3,370,000	$ 4,017,000
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant-date fair values of options awarded	$ 22.13	$ 24.49	$ 14.70
Intrinsic values of options exercised	$ 3,879,000	$ 5,232,000	$ 6,620,000
Unrecognized compensation cost	$ 1,655,000
Weighted average period for amortization of unrecognized compensation cost	1 year 8 months 12 days
Actual tax benefit recognized for the tax deductions from stock based compensation	$ 548,000	$ 1,455,000	$ 1,899,000
Stock Option Granted Prior to 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Stock Options Granted in 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Percentage of awards vesting in each year	33.33%
Stock Options Granted in 2018 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Percentage of awards vesting in each year	33.33%
Performance Stock Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance stock awards vested	0
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 3,180,000
Weighted average period for amortization of unrecognized compensation cost	1 year 8 months 12 days
Performance stock awards vested	119,501
Weighted-average grant-date fair values of awards granted	$ 72.06	$ 75.94	$ 41.81
SARs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Unrecognized compensation cost	$ 3,566,000
Weighted average period for amortization of unrecognized compensation cost	1 year 9 months 18 days
Weighted-average grant-date fair values of awards granted	$ 22.19	$ 24.90	$ 14.69
SARs liability cash-settled	$ 3,647,000	$ 4,760,000
SARs Granted Prior to 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
SARs Granted in 2017 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Percentage of awards vesting in each year	33.33%
SARs Granted in 2018 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Percentage of awards vesting in each year	33.33%
Maximum [Member] \| Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Minimum [Member] \| Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	8 years