Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Shares
Beginning Balance	3,539,961	3,091,474
Granted	425,426	800,000
Forfeited/Cancelled	(403,674)	(299,683)
Exercised	(213,008)	(51,830)
Ending Balance	3,348,705	3,539,961
Exercisable, December 31, 2013	2,084,463
Weighted Average Exercise Price
Beginning Balance	$ 5.66	$ 6.83
Granted	$ 3.89	$ 2.13
Forfeited/Cancelled	$ 14.19	$ 8.93
Exercised	$ 2.18	$ 2.31
Ending Balance	$ 4.70	$ 5.66
Exercisable, December 31, 2013	$ 4.43
Weighted Average Remaining Contractual Life (Years)
Outstanding, December 31, 2013	6 years 10 months 17 days
Exercisable, December 31, 2013	6 years 2 months 5 days
Stock Options Aggregate Intrinsic Value
Outstanding, December 31, 2013	$ 11,420
Exercisable, December 31, 2013	$ 7,721

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

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Number of share options (or share units) exercised during the current period.

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