Earnings per Common Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Common Share Computations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic:
Net (loss) income	$ (9,770)	$ (14,879)	$ (20,479)	$ 33,446
Weighted average common shares outstanding	59,400,317	55,388,774	58,735,351	54,949,901
Basic (loss) income per common share	$ (0.16)	$ (0.27)	$ (0.35)	$ 0.61
Effect of dilutive securities:
Net (loss) income	$ (9,770)	$ (14,879)	$ (20,479)	$ 33,446
Weighted average common shares outstanding	59,400,317	55,388,774	58,735,351	54,949,901
Effect of dilutive options and warrants				886,868
Diluted weighted average common shares outstanding	59,400,317	55,388,774	58,735,351	55,836,769
Diluted (loss) income per common share	$ (0.16)	$ (0.27)	$ (0.35)	$ 0.60