Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated (Deficit)	Accumulated (Deficit) Cumulative Effect, Period of Adoption, Adjustment
Beginning balance at Dec. 31, 2018	$ 428,340	$ (502)	$ 573	$ 1,006,822	$ 0	$ (579,055)	$ (502)
Beginning balance (in shares) at Dec. 31, 2018			57,331,622		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock (in shares)					(23,952,756)
Purchase of treasury stock (see Note 9)	(437,962)				$ (437,962)
Exercise of stock options (in shares)			111,660
Exercise of stock options	1,880		$ 1	1,879
Net (loss) income	37,557					37,557
Ending balance at Sep. 30, 2019	29,313		$ 574	1,008,701	$ (437,962)	(542,000)
Ending balance (in shares) at Sep. 30, 2019			57,443,282		(23,952,756)
Beginning balance at Jun. 30, 2019	27,725		$ 573	1,006,822	$ (437,942)	(541,728)
Beginning balance (in shares) at Jun. 30, 2019			57,331,622		(23,952,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			111,660
Exercise of stock options	1,880		$ 1	1,879
Other	(20)				$ (20)
Net (loss) income	(272)					(272)
Ending balance at Sep. 30, 2019	29,313		$ 574	1,008,701	$ (437,962)	(542,000)
Ending balance (in shares) at Sep. 30, 2019			57,443,282		(23,952,756)
Beginning balance at Dec. 31, 2019	27,260		$ 574	1,008,701	$ (437,962)	(544,053)
Beginning balance (in shares) at Dec. 31, 2019			57,443,282		(23,952,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock (in shares)					(2,682,042)
Purchase of treasury stock (see Note 9)	(30,626)				$ (30,626)
Exercise of stock options (in shares)			26,109
Exercise of stock options	356		$ 1	355
Private placement (in shares)					68,857
Private placement (see Note 9)	444			(813)	$ 1,257
Net (loss) income	39,421					39,421
Ending balance at Sep. 30, 2020	36,855		$ 575	1,008,243	$ (467,331)	(504,632)
Ending balance (in shares) at Sep. 30, 2020			57,469,391		(26,565,941)
Beginning balance at Jun. 30, 2020	36,500		$ 574	1,009,001	$ (468,588)	(504,487)
Beginning balance (in shares) at Jun. 30, 2020			57,463,943		(26,634,798)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			5,448
Exercise of stock options	56		$ 1	55
Private placement (in shares)					68,857
Private placement (see Note 9)	444			(813)	$ 1,257
Net (loss) income	(145)					(145)
Ending balance at Sep. 30, 2020	$ 36,855		$ 575	$ 1,008,243	$ (467,331)	$ (504,632)
Ending balance (in shares) at Sep. 30, 2020			57,469,391		(26,565,941)