Reconciliation of Numerator and Denominator Used in Computation of Basic and Diluted Net Income Loss per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Net loss used for basic calculation	$ (20,501)	$ (3,460)	$ (37,477)	$ (14,201)
Effect of revaluation of warrant liability		(873)
Adjusted net loss used for diluted calculation	$ (20,501)	$ (4,333)	$ (37,477)	$ (14,201)
Denominator
Basic weighted average number of common shares outstanding	69,791	54,875	66,464	54,130
Effect of dilutive potential common shares resulting from warrants		502
Diluted weighted average number of common shares outstanding	69,791	55,377	66,464	54,130
Net loss per common share:
Basic	$ (0.29)	$ (0.06)	$ (0.56)	$ (0.26)
Diluted	$ (0.29)	$ (0.08)	$ (0.56)	$ (0.26)