CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ 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, 2017	$ 12	$ 4,967	$ (160)	$ 101,744		$ 106,563
Balance (in shares) at Dec. 31, 2017	12,103
Net income				55,789		55,789
Share-based compensation		3,124				3,124
Share-based compensation (in shares)	19
Options exercised by executives and directors		547				547
Options exercised by executives and directors (in shares)	34
Net shares repurchased for employee taxes		(720)				$ (720)
Net shares repurchased for employee taxes, (in shares)	(7)					(0)
Restricted shares forfeitures	(40)
Treasury stock from stock repurchases (in shares)	8
Treasury stock from stock repurchases					$ (29,995)	$ (29,995)
Other comprehensive income			(13)			(13)
Cash dividends declared to stockholders				(26,189)		(26,189)
Balance at Dec. 31, 2018	$ 12	8,802	(173)	131,344	(30,879)	109,106
Balance (in shares) at Dec. 31, 2018	12,117
Treasury stock from cashless options		884			(884)
Net income				77,916		77,916
Share-based compensation	$ 273	4,520				4,520
Options exercised by executives and directors		278				278
Options exercised by executives and directors (in shares)	10
Net shares repurchased for employee taxes		(13,600)		(492)		$ (14,092)
Net shares repurchased for employee taxes, (in shares)	(128)					(100)
Treasury stock from stock repurchases					(33,114)	$ (33,114)
Other comprehensive income			198			198
Cash dividends declared to stockholders				(39,980)		(39,980)
Balance at Dec. 31, 2019	$ 12		25	168,788	(63,993)	104,832
Balance (in shares) at Dec. 31, 2019	12,272
Net income				102,859		102,859
Share-based compensation		6,796				6,796
Share-based compensation (in shares)	17
Options exercised by executives and directors		1,597				1,597
Options exercised by executives and directors (in shares)	28
Net shares repurchased for employee taxes		(551)				$ (551)
Net shares repurchased for employee taxes, (in shares)	(6)					(0)
Retirement of treasury stock	$ (489)			(63,993)	63,993
Treasury stock from stock repurchases					(5,000)	$ (5,000)
Other comprehensive income			16			16
Cash dividends declared to stockholders				(53,303)		(53,303)
Balance at Dec. 31, 2020	$ 12	$ 7,842	$ 41	$ 154,351	$ (5,000)	$ 157,246
Balance (in shares) at Dec. 31, 2020	11,822