Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Accumulated Deficit) [Member]
BALANCE at Dec. 31, 2020	$ 555,907	$ 873	$ (246,088)	$ 658,423	$ 364	$ 142,335
BALANCE, shares at Dec. 31, 2020		87,265,000
BALANCE, shares at Dec. 31, 2020			(17,203,000)
Net income	57,402					57,402
Foreign currency translation	(101)				(101)
Unrealized loss on investments, net of tax	(243)				(243)
Treasury stock purchased	(5,372)		$ (5,372)
Treasury stock purchased, shares			(440,000)
Share-based compensation expense	7,430			7,430
Common stock issued	(1,411)	$ 6	$ (2,034)	617
Common stock issued, shares		620,000	(160,000)
BALANCE at Jun. 30, 2021	613,612	$ 879	$ (253,494)	666,470	20	199,737
BALANCE, shares at Jun. 30, 2021		87,885,000
BALANCE, shares at Jun. 30, 2021			(17,803,000)
BALANCE at Mar. 31, 2021	588,345	$ 878	$ (248,120)	662,485	14	173,088
BALANCE, shares at Mar. 31, 2021		87,795,000
BALANCE, shares at Mar. 31, 2021			(17,363,000)
Net income	26,649					26,649
Foreign currency translation	28				28
Unrealized loss on investments, net of tax	(22)				(22)
Treasury stock purchased	(5,372)		$ (5,372)
Treasury stock purchased, shares			(440,000)
Share-based compensation expense	3,677			3,677
Common stock issued	307	$ 1	$ (2)	308
Common stock issued, shares		90,000
BALANCE at Jun. 30, 2021	613,612	$ 879	$ (253,494)	666,470	20	199,737
BALANCE, shares at Jun. 30, 2021		87,885,000
BALANCE, shares at Jun. 30, 2021			(17,803,000)
BALANCE at Dec. 31, 2021	$ 650,110	$ 887	$ (276,895)	674,242	(96)	251,972
BALANCE, shares at Dec. 31, 2021	88,724,438	88,724,000
BALANCE, shares at Dec. 31, 2021	(19,975,776)		(19,976,000)
Net income	$ 57,845					57,845
Foreign currency translation	(245)				(245)
Unrealized loss on investments, net of tax	(2,833)				(2,833)
Treasury stock purchased	(15,670)		$ (15,670)
Treasury stock purchased, shares			(1,480,000)
Share-based compensation expense	4,316			4,316
Common stock issued	(763)	$ 7	$ (1,612)	842
Common stock issued, shares		635,000	(146,000)
BALANCE at Jun. 30, 2022	$ 692,760	$ 894	$ (294,177)	679,400	(3,174)	309,817
BALANCE, shares at Jun. 30, 2022	89,358,511	89,359,000
BALANCE, shares at Jun. 30, 2022	(21,601,958)		(21,602,000)
BALANCE at Mar. 31, 2022	$ 678,380	$ 893	$ (282,333)	677,311	(1,541)	284,050
BALANCE, shares at Mar. 31, 2022		89,264,000
BALANCE, shares at Mar. 31, 2022			(20,485,000)
Net income	25,767					25,767
Foreign currency translation	(164)				(164)
Unrealized loss on investments, net of tax	(1,469)				(1,469)
Treasury stock purchased	(11,842)		$ (11,842)
Treasury stock purchased, shares			(1,117,000)
Share-based compensation expense	1,900			1,900
Common stock issued	188	$ 1	$ (2)	189
Common stock issued, shares		95,000
BALANCE at Jun. 30, 2022	$ 692,760	$ 894	$ (294,177)	$ 679,400	$ (3,174)	$ 309,817
BALANCE, shares at Jun. 30, 2022	89,358,511	89,359,000
BALANCE, shares at Jun. 30, 2022	(21,601,958)		(21,602,000)