Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2014
Options Outstanding
Beginning balance (shares)	6,969,303
Granted (shares)	184,250
Exercised (shares)	(159,332)
Forfeited (shares)	(214,223)
Ending balance (shares)	6,779,998
Vested and expected to vest (shares)	6,577,603
Exercisable (shares)	4,755,993
Weighted-Average Exercise Price per Share
Beginning balance (USD per share)	$ 6.38
Granted (USD per share)	$ 12.00
Exercised (USD per share)	$ 6.39
Forfeited (USD per share)	$ 9.82
Ending balance (USD per share)	$ 6.42
Vested and expected to vest (USD per share)	$ 6.32
Exercisable (USD per share)	$ 5.12
Weighted- Average Remaining Contractual Life
Balance (in years)	6 years 5 months 15 days
Vested and expected to vest (in years)	6 years 4 months 22 days
Exercisable (in years)	5 years 6 months 14 days
Aggregate Intrinsic Value
Balance	$ 42,797
Vested and expected to vest	42,141
Exercisable	$ 36,147

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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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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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

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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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