Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Outstanding [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Deficit) [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, beginning at Dec. 31, 2014	$ (18,502)		$ 406	$ 118,419	$ (11,343)	$ (90,918)	$ (35,066)
Balance, Shares beginning at Dec. 31, 2014		34,056,468
Stock-based compensation	2,768			2,768
Exercise of stock options	$ 3,436		5	3,431
Exercise of stock options, Shares	512,474	512,474
Other comprehensive income (loss), net	$ 34,835						34,835
Net income (loss)	(84,867)				(84,867)
Balance, ending at Dec. 31, 2015	(62,330)		411	124,618	(96,210)	(90,918)	(231)
Balance, Shares ending at Dec. 31, 2015		34,568,942
Stock-based compensation	3,843			3,843
Exercise of stock options	$ 1,733		3	1,730
Exercise of stock options, Shares	296,103	296,103
Settlement of restricted stock units			2	(2)
Settlement of restricted stock units, Shares		183,293
Acquisition of treasury stock			0
Other comprehensive income (loss), net	$ 14,255						14,255
Net income (loss)	(29,615)				(29,615)
Balance, ending at Dec. 31, 2016	$ (72,114)		416	130,189	(125,825)	(90,918)	14,024
Balance, Shares ending at Dec. 31, 2016	35,048,338	35,048,338
Stock-based compensation	$ 2,336			2,336
Exercise of stock options	$ 3,744		6	3,738
Exercise of stock options, Shares	539,183	539,183
Settlement of restricted stock units			4	(4)
Settlement of restricted stock units, Shares		397,522
Acquisition of treasury stock	$ (11,401)		0			(11,401)
Acquisition of treasury stock, Shares	(1,795,444)	(1,795,444)
Other comprehensive income (loss), net	$ (47,138)						(47,138)
Net income (loss)	84,936				84,936
Balance, ending at Dec. 31, 2017	$ (39,637)		$ 426	$ 136,259	$ (40,889)	$ (102,319)	$ (33,114)
Balance, Shares ending at Dec. 31, 2017	34,189,599	34,189,599