CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock, Common [Member]
BALANCE at Dec. 31, 2021	$ 1,099,914	$ 2	$ 491	$ 658,728	$ 500,212	$ (18,235)	$ (41,284)
BALANCE (in shares) at Dec. 31, 2021		200,000	49,065,924				1,365,648
Net income	144,927				144,927
Other comprehensive loss	(6,321)					(6,321)
Cash dividend	(42,740)				(42,740)
Issuance of common stock to employees	22,147			22,147
Issuance of common stock to employees (in shares)			70,887
Shares withheld for employee taxes	(9,150)			(9,150)
Shares withheld for employee taxes (in shares)			(31,334)
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,421		$ 10,022	1,421
Issuance of common stock to employees under an ESPP	1,627		13,026	1,627
BALANCE at Sep. 30, 2022	1,211,825	$ 2	$ 491	674,773	602,399	(24,556)	$ (41,284)
BALANCE (in shares) at Sep. 30, 2022		200,000	49,128,525				1,365,648
BALANCE at Jun. 30, 2022	1,165,309	$ 2	$ 491	666,087	563,191	(23,178)	$ (41,284)
BALANCE (in shares) at Jun. 30, 2022		200,000	49,115,444				1,365,648
Net income	53,455				53,455
Other comprehensive loss	(1,378)					(1,378)
Cash dividend	(14,247)				(14,247)
Issuance of common stock to employees	8,209			8,209
Issuance of common stock to employees (in shares)			8,753
Shares withheld for employee taxes	(306)			(306)
Shares withheld for employee taxes (in shares)			(2,852)
Issuance of common stock to Board of Directors and Scientific Advisory Board	347		$ 2,196	347
Issuance of common stock to employees under an ESPP	436		4,984	436
BALANCE at Sep. 30, 2022	1,211,825	$ 2	$ 491	674,773	602,399	(24,556)	$ (41,284)
BALANCE (in shares) at Sep. 30, 2022		200,000	49,128,525				1,365,648
BALANCE at Dec. 31, 2022	1,275,369	$ 2	$ 491	681,335	653,277	(18,452)	$ (41,284)
BALANCE (in shares) at Dec. 31, 2022		200,000	49,136,030				1,365,648
Net income	141,033				141,033
Other comprehensive loss	3,487					3,487
Cash dividend	(50,083)				(50,083)
Issuance of common stock to employees	16,947		$ 1	16,946
Issuance of common stock to employees (in shares)			139,826
Shares withheld for employee taxes	(7,895)			(7,895)
Shares withheld for employee taxes (in shares)			(56,504)
Cancellation of restricted stock awards			$ (5)	5
Cancellation of restricted stock awards (in shares)			(526,241)
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,564		$ 13,504	1,564
Issuance of common stock to employees under an ESPP	1,944		13,915	1,944
BALANCE at Sep. 30, 2023	1,382,366	$ 2	$ 487	693,899	744,227	(14,965)	$ (41,284)
BALANCE (in shares) at Sep. 30, 2023		200,000	48,720,530				1,365,648
BALANCE at Jun. 30, 2023	1,338,766	$ 2	$ 487	686,501	709,372	(16,312)	$ (41,284)
BALANCE (in shares) at Jun. 30, 2023		200,000	48,706,932				1,365,648
Net income	51,516				51,516
Other comprehensive loss	1,347					1,347
Cash dividend	(16,661)				(16,661)
Issuance of common stock to employees	6,738		$ 8,908	6,738
Shares withheld for employee taxes	(466)		(3,190)	(466)
Issuance of common stock to Board of Directors and Scientific Advisory Board	423		3,304	423
Issuance of common stock to employees under an ESPP	703		4,576	703
BALANCE at Sep. 30, 2023	$ 1,382,366	$ 2	$ 487	$ 693,899	$ 744,227	$ (14,965)	$ (41,284)
BALANCE (in shares) at Sep. 30, 2023		200,000	48,720,530				1,365,648