Stock-Based Compensation - Stock Based Compensation Stock Option Activity (Detail) (Stock Option [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding, Beginning Balance	1,433,179
Number of Options, Granted	0
Number of Options, Exercised	(122,202)
Number of Options, Forfeited	(2,730)
Number of Options, Outstanding, Ending Balance	1,308,247	1,433,179
Number of Options, Vested and exercisable at March 31, 2015	1,216,856
Number of Options, Available for grant at March 31, 2015	621,225
Weighted-Average Exercise Price, Outstanding, Beginning Balance	$ 16.23
Weighted-Average Exercise Price, Granted	$ 0
Weighted-Average Exercise Price, Exercised	$ 15.42
Weighted-Average Exercise Price, Forfeited	$ 24.77
Weighted-Average Exercise Price, Outstanding, Ending Balance	$ 16.29	$ 16.23
Weighted Average Exercise Price, Vested and exercisable	$ 15.67
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 17,889
Aggregate Intrinsic Value, Outstanding, Ending Balance	27,361	17,889
Aggregate Intrinsic Value, Vested and exercisable at March 31, 2015	$ 26,195
Weighted-Average Remaining Contractual Life (Years), Outstanding	4 years 2 months 1 day	4 years 5 months 19 days
Weighted-Average Remaining Contractual Life (Years), Vested and exercisable at March 31, 2015	4 years 4 days

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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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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

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-Publisher FASB

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- Definition

Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Number of options outstanding, including both vested and non-vested options.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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- Definition

As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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