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Shared-Based Payments - Schedule of Stock Option Activity (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding, Beginning Balance	3,249,702
Number of Options, Granted	687,183
Number of Options, Exercised	(1,025,933)
Number of Options, Forfeited or expired	(33,949)
Number of Options, Outstanding, Ending Balance	2,877,003	3,249,702
Number of Options, Exercisable	1,855,178
Number of Options, Vested and expected to vest	918,600
Weighted- Average Exercise Price, Outstanding, Beginning Balance	$ 0.94
Weighted- Average Exercise Price, Granted	$ 3.19
Weighted- Average Exercise Price, Exercised	$ 0.75
Weighted- Average Exercise Price, Forfeited or expired	$ 1.13
Weighted- Average Exercise Price, Outstanding, Ending Balance	$ 1.50	$ 0.94
Weighted- Average Exercise Price, Exercisable	$ 0.94
Weighted- Average Exercise Price, Vested and expected to vest	$ 2.44
Weighted Average Contractual Term, Granted	7 years
Weighted Average Contractual Term, Outstanding	7 years 3 months 12 days	7 years 3 months 18 days

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Share based compensation arrangement by share based payment award options granted weighted average remaining contractual term.

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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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-Publisher FASB

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

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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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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 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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