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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator for Basic and Diluted:
Net loss used for basic calculation	$ (18,166)	$ (15,972)	$ (35,029)	$ (25,432)
Effect of revaluation of warrant liability				(3,589)
Adjusted net loss used for diluted calculation	$ (18,166)	$ (15,972)	$ (35,029)	$ (29,021)
Denominator:
Basic weighted average number of shares outstanding	101,563	95,728	100,517	94,576
Effect of dilutive potential shares				1,106
Diluted weighted average number of shares outstanding	101,563	95,728	100,517	95,682
Net loss per share:
Basic	$ (0.18)	$ (0.17)	$ (0.35)	$ (0.27)
Diluted	$ (0.18)	$ (0.17)	$ (0.35)	$ (0.30)