CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid- In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2019	$ 12		$ 25	$ 168,788	$ (63,993)	$ 104,832
Balance (in shares) at Dec. 31, 2019	12,272,000
Net income				18,477		18,477
Share-based compensation		$ 981				981
Share-based compensation (in shares)	7,000
Net shares repurchased for employee taxes		(487)				(487)
Net shares repurchased for employee taxes, (in shares)	(5,000)
Treasury stock retired from stock repurchases				(63,993)	63,993
Treasury stock retired from stock repurchases, (in shares)	(489,000)
Other comprehensive income			45			45
Cash dividends declared to stockholders				(13,099)		(13,099)
Balance at Mar. 31, 2020	$ 12	494	70	110,173		110,749
Balance (in shares) at Mar. 31, 2020	11,785,000
Balance at Dec. 31, 2019	$ 12		25	168,788	(63,993)	104,832
Balance (in shares) at Dec. 31, 2019	12,272,000
Net income						$ 40,412
Net shares repurchased for employee taxes, (in shares)						(5,208)
Other comprehensive income						$ 74
Balance at Jun. 30, 2020	$ 12	2,871	99	118,754	(5,000)	116,736
Balance (in shares) at Jun. 30, 2020	11,806,000
Balance at Mar. 31, 2020	$ 12	494	70	110,173		110,749
Balance (in shares) at Mar. 31, 2020	11,785,000
Net income				21,935		21,935
Share-based compensation		1,136				1,136
Options exercised by executives and directors		1,250				1,250
Options exercised by executives and directors (in shares)	21,000
Net shares repurchased for employee taxes		(9)				(9)
Treasury stock from stock repurchases					(5,000)	(5,000)
Other comprehensive income			29			29
Cash dividends declared to stockholders				(13,354)		(13,354)
Balance at Jun. 30, 2020	$ 12	2,871	99	118,754	(5,000)	116,736
Balance (in shares) at Jun. 30, 2020	11,806,000
Balance at Dec. 31, 2020	$ 12	7,842	41	154,351	(5,000)	157,246
Balance (in shares) at Dec. 31, 2020	11,822,000
Net income				41,063		41,063
Share-based compensation		2,198				2,198
Share-based compensation (in shares)	13,000
Options exercised by executives and directors		481				481
Options exercised by executives and directors (in shares)	11,000
Net shares repurchased for employee taxes		(1,807)				(1,807)
Net shares repurchased for employee taxes, (in shares)	(7,000)
Treasury stock from stock repurchases					(7,500)	(7,500)
Other comprehensive income			62			62
Cash dividends declared to stockholders				(16,852)		(16,852)
Balance at Mar. 31, 2021	$ 12	8,714	103	178,562	(12,500)	174,891
Balance (in shares) at Mar. 31, 2021	11,839,000
Balance at Dec. 31, 2020	$ 12	7,842	41	154,351	(5,000)	157,246
Balance (in shares) at Dec. 31, 2020	11,822,000
Net income						$ 88,026
Net shares repurchased for employee taxes, (in shares)						(6,927)
Other comprehensive income						$ 34
Balance at Jun. 30, 2021	$ 12	10,606	75	185,343	(1,347)	194,689
Balance (in shares) at Jun. 30, 2021	11,738,000
Balance at Mar. 31, 2021	$ 12	8,714	103	178,562	(12,500)	174,891
Balance (in shares) at Mar. 31, 2021	11,839,000
Net income				46,963		46,963
Share-based compensation		1,697		142		1,839
Share-based compensation (in shares)	10,000
Options exercised by executives and directors		221				221
Options exercised by executives and directors (in shares)	3,000
Net shares repurchased for employee taxes		(26)				(26)
Treasury stock from stock repurchases					(12,230)	(12,230)
Treasury stock retired from stock repurchases				(23,383)	23,383
Treasury stock retired from stock repurchases, (in shares)	(114,000)
Other comprehensive income			(28)			(28)
Cash dividends declared to stockholders				(16,941)		(16,941)
Balance at Jun. 30, 2021	$ 12	$ 10,606	$ 75	$ 185,343	$ (1,347)	$ 194,689
Balance (in shares) at Jun. 30, 2021	11,738,000