CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Scenario, Previously Reported [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member] Common Stock [Member]	Scenario, Previously Reported [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member] Additional Paid- In Capital [Member]	Scenario, Previously Reported [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Scenario, Previously Reported [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member] Retained Earnings [Member]	Scenario, Previously Reported [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member]	Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Retained Earnings [Member]	Difference between Revenue Guidance in Effect before and after Topic 606 [Member]	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, 2016								$ 12	$ 2,672	$ (165)	$ 93,497		$ 96,016
Balance (in shares) at Dec. 31, 2016								12,027
Net income											27,721		27,721
Share-based compensation									4,267				4,267
Share-based compensation (in shares)								95
Options exercised by executives and directors									568				568
Options exercised by executives and directors (in shares)								25
Net shares repurchased for employee taxes									(2,540)				(2,540)
Net shares repurchased for employee taxes, (in shares)								(44)
Other comprehensive income (loss)										5			5
Cash dividends declared to stockholders											(17,456)		(17,456)
Balance at Dec. 31, 2017	$ 12	$ 4,967	$ (160)	$ 103,762	$ 108,581			$ 12	4,967	(160)	101,744		106,563
Balance (in shares) at Dec. 31, 2017	12,103							12,103
Cumulative effect adjustments from changes in accounting standards						$ (2,018)	$ (2,018)
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)
Restricted shares forfeitures								(40)
Treasury stock from cashless options									884			$ (884)
Treasury stock from cashless options, (in shares)								8
Treasury stock from stock repurchases												(29,995)	(29,995)
Other comprehensive income (loss)										(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
Net income											77,916		77,916
Share-based compensation									4,520				4,520
Share-based compensation (in shares)								273
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)
Treasury stock from stock repurchases												(33,114)	(33,114)
Other comprehensive income (loss)										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