Reconciliation of Numerator and Denominator Used in Computation of Basic and Diluted Net Income Loss per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator for Basic and Diluted:
Net loss used for basic calculation	$ (14,376)	$ (15,680)	$ (49,405)	$ (41,112)
Effect of revaluation of warrant liability		(1,109)		(4,698)
Adjusted net loss used for diluted calculation	$ (14,376)	$ (16,789)	$ (49,405)	$ (45,810)
Denominator:
Basic weighted average number of shares outstanding	102,769	96,864	101,273	95,347
Effect of dilutive potential shares		741		993
Diluted weighted average number of shares outstanding	102,769	97,605	101,273	96,340
Net loss per share:
Basic	$ (0.14)	$ (0.16)	$ (0.49)	$ (0.43)
Diluted	$ (0.14)	$ (0.17)	$ (0.49)	$ (0.48)