Stock-based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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	1,971,353
Compensation expenses (income) charged against income	$ (69)	$ 2,783	$ 3,122
Income tax benefit (expense) recognized in the income statement for share-based compensation arrangements	(26)	1,059	1,186
Proceeds from stock option exercises	1,754	3,977	4,473
Actual tax benefit recognized for the tax deductions from stock options exercise	640	3,440	7,237
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Weighted-average grant-date fair values of options awarded	$ 23.77	$ 23.08	$ 15.73
Intrinsic values of options exercised	2,071	9,138	17,163
Unrecognized compensation cost	774
Weighted average period for amortization of unrecognized compensation cost	1 year
Actual tax benefit recognized for the tax deductions from stock options exercise	568	2,786	6,411
Stock Option [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Stock Option [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	8 years
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	1,365
Weighted average period for amortization of unrecognized compensation cost	2 years
Weighted-average grant-date fair values of awards granted	$ 59.52	$ 60.75	$ 41.00
SARs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period of expiration	10 years
Vesting period	2 years
Unrecognized compensation cost	693
Weighted average period for amortization of unrecognized compensation cost	1 year 1 month 6 days
Weighted-average grant-date fair values of awards granted	$ 23.74	$ 23.12	$ 15.73
SARs liability	$ 1,457	$ 2,172

allocated share based compensation expense income.

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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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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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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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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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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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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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