Equity Incentive Plans - Summary of Stock Option and Restricted Stock Bonus Activities (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding Beginning Balance, Number of Options	2,944,645	3,077,481	2,008,960
Granted, Number of Options	310,000	455,000	1,319,500
Forfeited, Number of Options	(31,905)	(8,360)	(95,271)
Exercised, Number of Options	(6,795)	(579,476)	(155,708)
Outstanding Ending Balance, Number of Options	3,215,945	2,944,645	3,077,481	2,008,960
Vested and expected to vest, Number of Options	3,204,967	2,916,184	3,021,937
Exercisable, Number of Options	2,760,402	1,946,475	1,726,891
Outstanding Beginning Balance, Weighted Average Exercise Price of Stock Options	$ 8.82	$ 7.35	$ 6.79
Granted, Weighted Average Exercise Price of Stock Options	$ 16.75	$ 17.08	$ 8.29
Forfeited, Weighted Average Exercise Price of Stock Options	$ 8.34	$ 10.89	$ 11.07
Exercised, Weighted Average Exercise Price of Stock Options	$ 7.03	$ 7.44	$ 5.88
Outstanding Ending Balance, Weighted Average Exercise Price of Stock Options	$ 9.60	$ 8.82	$ 7.35	$ 6.79
Vested and expected to vest, Weighted Average Exercise Price of Stock Options	$ 9.58	$ 8.78	$ 7.32
Exercisable, Weighted Average Exercise Price of Stock Options	$ 8.70	$ 7.00	$ 6.54
Outstanding Beginning Balance, Aggregate Intrinsic Value of Stock Options	$ 31,558	$ 26,385	$ 2,773
Outstanding Ending Balance, Aggregate Intrinsic Value of Stock Options	39,615	31,558	26,385	2,773
Vested and expected to vest, Aggregate Intrinsic Value of Stock Options	39,610	31,376	25,988
Exercisable, Aggregate Intrinsic Value of Stock Options	$ 39,187	$ 24,325	$ 16,203
Outstanding, Weighted Average Remaining Contractual Life of Stock Options	6 years 7 months 6 days	7 years 3 months 18 days	7 years 10 months 24 days	8 years 1 month 6 days
Vested and expected to vest, Weighted Average Remaining Contractual Life of Stock Options	6 years 7 months 6 days	7 years 3 months 18 days	7 years 10 months 24 days
Exercisable, Weighted Average Remaining Contractual Life of Stock Options	6 years 3 months 18 days	6 years 8 months 12 days	7 years

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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

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

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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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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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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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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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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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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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