CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Series A Nonconvertible Preferred Stock [Member] Preferred Stock [Member]
BALANCE at Dec. 31, 2020	$ 912,714	$ 490	$ 635,595	$ 353,930	$ (36,019)	$ (41,284)	$ 2
BALANCE (in shares) at Dec. 31, 2020		49,013,476				1,365,648	200,000
Net income	51,687			51,687
Other comprehensive income (loss)	1,010				1,010
Cash dividend	(9,487)			9,487
Issuance of common stock to employees	5,116	$ 1	5,115
Issuance of common stock to employees (in shares)		53,123
Shares withheld for employee taxes	(9,634)		9,634
Shares withheld for employee taxes (in shares)		22,048
Issuance of common stock to Board of Directors and Scientific Advisory Board	630		630
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		4,443
Issuance of common stock to employees under an ESPP	432		432
Issuance of common stock to employees under an ESPP (in shares)		1,782
BALANCE at Mar. 31, 2021	952,468	$ 491	632,138	396,130	(35,009)	$ (41,284)	$ 2
BALANCE (in shares) at Mar. 31, 2021		49,050,776				1,365,648	200,000
BALANCE at Dec. 31, 2021	1,099,914	$ 491	658,728	500,212	(18,235)	$ (41,284)	$ 2
BALANCE (in shares) at Dec. 31, 2021		49,065,924				1,365,648	200,000
Net income	49,970			49,970
Other comprehensive income (loss)	(3,660)				(3,660)
Cash dividend	(14,246)			14,246
Issuance of common stock to employees	5,979		5,979
Issuance of common stock to employees (in shares)		47,748
Shares withheld for employee taxes	(7,896)		7,896
Shares withheld for employee taxes (in shares)		22,347
Issuance of common stock to Board of Directors and Scientific Advisory Board	730		730
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		5,630
Issuance of common stock to employees under an ESPP	509		509
Issuance of common stock to employees under an ESPP (in shares)		2,875
BALANCE at Mar. 31, 2022	$ 1,131,300	$ 491	$ 658,050	$ 535,936	$ (21,895)	$ (41,284)	$ 2
BALANCE (in shares) at Mar. 31, 2022		49,099,830				1,365,648	200,000