Information Regarding Stock Options Outstanding Stock Options Vested and Expected to Vest and Stock Options Exercisable (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Stock options outstanding	11,323	10,405
Stock options vested and expected to vest	10,920
Stock options exercisable	7,006
Weighted Average Exercise Price
Stock options outstanding	$ 4.13	$ 3.46
Stock options vested and expected to vest	$ 4.08
Stock options exercisable	$ 3.70
Weighted Average Remaining Contractual (Years)
Stock options outstanding	6 years 9 months 18 days
Stock options vested and expected to vest	6 years 8 months 12 days
Stock options exercisable	5 years 8 months 12 days
Aggregate intrinsic value
Stock options outstanding	$ 25,517
Stock options vested and expected to vest	25,174
Stock options exercisable	$ 19,324

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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 number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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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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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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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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