Reconciliation of Numerator and Denominator Used in Computation of Basic and Diluted Net Income Loss per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Numerator for Basic and Diluted:
Net loss used for basic calculation	$ (9,460)us-gaap_NetIncomeLoss	$ (225)us-gaap_NetIncomeLoss
Effect of revaluation of warrant liability	(6,296)us-gaap_DilutiveSecurities	(9,034)us-gaap_DilutiveSecurities
Adjusted net loss used for diluted calculation	$ (15,756)	$ (9,259)
Denominator:
Basic weighted average number of shares outstanding	93,411	72,088
Effect of dilutive potential shares	1,251	3,070
Diluted weighted average number of shares outstanding	94,662	75,158
Net loss per share:
Basic	$ (0.10)us-gaap_EarningsPerShareBasic	$ 0.00us-gaap_EarningsPerShareBasic
Diluted	$ (0.17)us-gaap_EarningsPerShareDiluted	$ (0.12)us-gaap_EarningsPerShareDiluted

Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise stock options, restrictive stock units (RSUs), convertible preferred stock of an employee stock ownership plan (ESOP), and other dilutive convertible securities.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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