Net Income (Loss) Per Share - Calculations of Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic:
Net income (loss)	$ 32,060	$ (18,650)	$ 994	$ (69,844)
Weighted average common shares outstanding (in shares)	20,561	20,455	20,535	20,416
Net income (loss) per share (in dollars per share)	$ 1.56	$ (0.91)	$ 0.05	$ (3.42)
Diluted:
Unvested restricted stock and DSU's	0	0	0	0
Employee stock options	0	0	0	0
Weighted average common shares outstanding	$ 20,561	$ 20,455	$ 20,535	$ 20,416
Net income (loss) for dilutive share computation	$ 0	$ 0	$ 0	$ 0