Earnings per Common Share - Reconciliation of Numerators and Denominators of Basic and Diluted Loss Per Share Computations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic:
Net income (loss)	$ (14,879)	$ (16,486)	$ 33,446	$ (35,219)
Weighted average common shares outstanding	55,388,774	53,594,979	54,949,901	53,412,813
Basic income (loss) per common share	$ (0.27)	$ (0.31)	$ 0.61	$ (0.66)
Effect of dilutive securities:
Net income (loss)	$ (14,879)	$ (16,486)	$ 33,446	$ (35,219)
Weighted average common shares outstanding	55,388,774	53,594,979	54,949,901	53,412,813
Effect of dilutive options and warrants			886,868
Diluted weighted average common shares outstanding	55,388,774	53,594,979	55,836,769	53,412,813
Diluted income (loss) per common share	$ (0.27)	$ (0.31)	$ 0.60	$ (0.66)