Consolidated Statement of Shareholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Balances at Dec. 31, 2015	$ 547,190	$ 450	$ 812,160	$ (254,120)	$ (11,300)
Net income (loss)	(39,800)			(39,800)
Other comprehensive income (loss)	(13,100)				(13,100)
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(1,590)		(1,590)
Stock option exercises and restricted stock vesting	160	10	150
Tax effect from stock based compensation	(80)		(80)
Non-cash compensation expense	6,940		6,940
Balances at Dec. 31, 2016	499,720	460	817,580	(293,920)	(24,400)
Net income (loss)	30,960			30,960
Other comprehensive income (loss)	7,070				7,070
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(510)		(510)
Non-cash compensation expense	6,780		6,780
Balances at Dec. 31, 2017	544,020	460	823,850	(262,960)	(17,330)
Net income (loss)	83,300			83,300
Other comprehensive income (loss)	480				480
Stock Repurchased and Retired During Period, Value	(12,140)		(12,140)
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(2,380)		(2,380)
Non-cash compensation expense	7,170		7,170
Balances at Dec. 31, 2018	$ 620,450	$ 460	$ 816,500	$ (179,660)	$ (16,850)