Net Loss Per Share - Computation of Net (Loss) Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss	$ (4,153)	$ (18,724)	$ (2,346)	$ (25,562)	$ (2,976)	$ (11,539)	$ (3,563)	$ (27,641)	$ (50,785)	$ (45,719)	$ (62,134)
Weighted average shares-basic (shares)									64,882,417	64,708,163	60,729,128
Net (loss) income per share-basic ($ per share)	$ (0.07)	$ (0.28)	$ (0.04)	$ (0.39)	$ (0.05)	$ (0.18)	$ (0.06)	$ (0.44)	$ (0.78)	$ (0.71)	$ (1.02)
Weighted average shares-diluted (shares)									64,882,417	64,708,163	60,729,128
Net (loss) income per share-diluted ($ per share)	$ (0.07)	$ (0.28)	$ (0.04)	$ (0.39)	$ (0.05)	$ (0.18)	$ (0.06)	$ (0.44)	$ (0.78)	$ (0.71)	$ (1.02)