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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic:
Net income (loss)	$ 38,976	$ (19,022)	$ 23,524	$ (33,625)
Weighted average common shares outstanding (in shares)	20,333	20,895	20,391	20,878
Net income (loss) per share (in dollars per share)	$ 1.92	$ (0.91)	$ 1.15	$ (1.61)
Diluted:
Interest on convertible senior debentures	$ 1,119	$ 0	$ 2,229	$ 0
Net income (loss) for dilutive share computation	$ 40,095	$ (19,022)	$ 25,753	$ (33,625)
Weighted average common shares outstanding (in shares)	23,539	20,895	23,602	20,878
Net income (loss) per share (in dollars per share)	$ 1.70	$ (0.91)	$ 1.09	$ (1.61)
Restricted Stock Unit And Performance Stock Unit And Deferred Stock Unit
Diluted:
Unvested restricted stock, DSUs, and employee stock options (in shares)	148	0	155	0
Employee stock options
Diluted:
Unvested restricted stock, DSUs, and employee stock options (in shares)	24	0	22	0
Convertible Senior Debentures due 2018
Diluted:
Convertible senior debentures (in shares)	3,034	0	3,034	0