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

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-Section 50

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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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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 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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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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Share-based Compensation Arrangement by Share-based Payment Award, Number of Plans

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Share Based Compensation Arrangements By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value

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Share Based Compensation Arrangements By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value

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Stock-Based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 plan	Dec. 31, 2013	Dec. 31, 2012	May 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized				3,800,000
Number of stock-based compensation plans	4
Total stock-based compensation cost recognized	$ 13,790	$ 9,429	$ 11,016
Shares exercised, total intrinsic value	1,543	3,632	10,555
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	4,068
Compensation cost expected recognition weighted average period	1 year 2 months 12 days
Shares granted fair value	7,376	9,757	7,830
Shares vested fair value	8,545	5,259	6,347
Restricted Stock Units (RSUs) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted Stock Units (RSUs) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Deferred Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted and vested fair value	189	137	150
Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost expected recognition weighted average period	1 year 10 months 24 days
Shares vested fair value	2,474	9,075	1,382
Performance Based Restricted Stock Units \| Units At Threshold
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	3,886
Performance Based Restricted Stock Units \| Units At Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	11,058
Shares granted fair value	19,239	5,356	4,308
Performance Based Restricted Stock Units \| Units At Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	$ 20,910
Performance Based Restricted Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance goals tracking period	1 year
Performance Based Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance goals tracking period	4 years