Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Outstanding January 1, 2014	9,330,000
Granted	3,271,000
Cancelled/Expired	(1,696,000)
Exercised	(234,500)	(386,000)
Outstanding, December 31, 2014	10,670,000	9,330,000
Exercisable, December 31, 2014	7,263,000
Vested and Expected to Vest, December 31, 2014	1,630,000
Available for future grant at December 31, 2014	5,578,000
Weighted Average Exercise Price
Outstanding January 1, 2014	$ 6.64
Granted	$ 1.99
Cancelled/Expired	$ 9.02
Exercised	$ 1.31
Outstanding, December 31, 2014	$ 4.95	$ 6.64
Exercisable, December 31, 2014	$ 5.33
Vested and Expected to Vest, December 31, 2014	$ 6.03
Weighted Average Remaining Contractual Term
Outstanding, December 31, 2014	7 years 8 months 12 days
Exercisable, December 31, 2014	7 years 3 months 18 days
Vested and Expected to Vest, December 31, 2014	8 years 2 months 12 days
Aggregate Intrinsic Value
Outstanding, December 31, 2014	$ 0
Exercisable, December 31, 2014	0
Vested and Expected to Vest, December 31, 2014	$ 0

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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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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 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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