Summary of Stock Options Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shares issuable under options
Shares issuable under options, beginning balance	591,427	916,094	440,301
Shares issuable under options, granted	718,903	7,961	475,793
Shares issuable under options, exercised		(16,069)
Shares issuable under options, forfeited		(316,559)
Shares issuable under options, ending balance	1,310,330	591,427	916,094	440,301
Shares issuable under options, options vested and expected to vest	1,310,330
Shares issuable under options, options exercisable	657,317
Weighted-average exercise price
Weighted-average exercise price, beginning balance	$ 1.00	$ 1.19	$ 0.75
Weighted-average exercise price, granted	$ 2.64	$ 1.57	$ 1.57
Weighted-average exercise price, exercised		$ 0.88
Weighted-average exercise price, forfeited		$ 1.57
Weighted-average exercise price, ending balance	$ 1.88	$ 1.00	$ 1.19	$ 0.75
Weighted-average exercise price, options vested and expected to vest	$ 1.88
Weighted-average exercise price, options exercisable	$ 1.26
Weighted-average remaining contractual life
Weighted-average remaining contractual life	7 years 9 months 18 days	7 years 1 month 6 days	8 years 8 months 12 days	8 years 6 months
Weighted-average remaining contractual life, options vested and expected to vest	7 years 9 months 18 days
Weighted-average remaining contractual life, options exercisable	6 years 7 months 6 days
Aggregate intrinsic value
Aggregate intrinsic value, beginning balance	$ 342	$ 354		$ 216
Aggregate intrinsic value, ending balance	10,185	342	354
Aggregate intrinsic value, options vested and expected to vest	10,185
Aggregate intrinsic value, options exercisable	$ 5,543

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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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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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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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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