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 Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Accumulated (Deficit)
Beginning balance at Dec. 31, 2019	$ 27,260		$ 574	$ 1,008,701	$ (437,962)	$ 0		$ (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	(30,626)				$ (30,626)
Exercise of stock options (in shares)			20,661
Exercise of stock options	300			300
Net income	39,566							39,566
Ending balance at Jun. 30, 2020	36,500		$ 574	1,009,001	$ (468,588)	0		(504,487)
Ending balance (in shares) at Jun. 30, 2020			57,463,943		(26,634,798)
Beginning balance at Mar. 31, 2020	33,892		$ 574	1,009,001	$ (459,732)	0		(515,951)
Beginning balance (in shares) at Mar. 31, 2020			57,463,943		(25,805,102)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock (in shares)					(829,696)
Purchase of treasury stock	(8,856)				$ (8,856)
Net income	11,464							11,464
Ending balance at Jun. 30, 2020	36,500		$ 574	1,009,001	$ (468,588)	0		(504,487)
Ending balance (in shares) at Jun. 30, 2020			57,463,943		(26,634,798)
Beginning balance at Dec. 31, 2020	$ 196,775	$ (4,445)	$ 596	1,059,624	$ (468,613)	0	$ (4,445)	(394,832)
Beginning balance (in shares) at Dec. 31, 2020			59,590,422		(26,678,410)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock (in shares)	0
Exercise of stock options (in shares)			239,275
Exercise of stock options	$ (1,070)		$ 2	(1,072)
Exercise of stock warrants (in shares)			561,900
Exercise of stock warrants	13,686		$ 6	13,680
Stock compensation expense	3,892			3,892
Net income	60,865							60,865
Ending balance at Jun. 30, 2021	269,703		$ 604	1,076,124	$ (468,613)	(4,445)		(333,967)
Ending balance (in shares) at Jun. 30, 2021			60,391,597		(26,678,410)
Beginning balance at Mar. 31, 2021	$ 229,196	$ (1,478)	$ 598	1,058,504	$ (468,613)	(2,967)	$ (1,478)	(358,326)
Beginning balance (in shares) at Mar. 31, 2021			59,806,077		(26,678,410)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock (in shares)	0
Exercise of stock options (in shares)			23,731
Exercise of stock options	$ 2,024			2,024
Exercise of stock warrants (in shares)			561,789
Exercise of stock warrants	13,681		$ 6	13,675
Stock compensation expense	1,921			1,921
Net income	24,359							24,359
Ending balance at Jun. 30, 2021	$ 269,703		$ 604	$ 1,076,124	$ (468,613)	$ (4,445)		$ (333,967)
Ending balance (in shares) at Jun. 30, 2021			60,391,597		(26,678,410)