CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Scenario, Previously Reported [Member] Common Stock [Member]	Scenario, Previously Reported [Member] Additional Paid- In Capital [Member]	Scenario, Previously Reported [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Scenario, Previously Reported [Member] Retained Earnings [Member]	Scenario, Previously Reported [Member]	Common Stock [Member]	Additional Paid- In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Cumulative effect adjustments from changes in accounting standards									$ (2,018)		$ (2,018)
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
Net income									12,222		12,222
Share-based compensation							805				805
Share-based compensation (in shares)						16
Options exercised by executives and directors							62				62
Options exercised by executives and directors (in shares)						14
Net shares repurchased for employee taxes							(215)				(215)
Net shares repurchased for employee taxes, (in shares)						(3)
Treasury stock from cashless options							750			$ (750)
Treasury stock from cashless options, (in shares)						9
Other comprehensive income (loss)								(84)			(84)
Cash dividends declared to stockholders									(5,723)		(5,723)
Balance at Mar. 31, 2018						$ 12	6,369	(244)	108,243	(750)	113,630
Balance (in shares) at Mar. 31, 2018						12,139
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
Net income											26,355
Net shares repurchased for employee taxes, (in shares)						(3)
Other comprehensive income (loss)											(59)
Balance at Jun. 30, 2018						$ 12	7,199	(219)	116,617	(20,746)	102,863
Balance (in shares) at Jun. 30, 2018						12,141
Balance at Mar. 31, 2018						$ 12	6,369	(244)	108,243	(750)	113,630
Balance (in shares) at Mar. 31, 2018						12,139
Net income									14,133		14,133
Share-based compensation							830				830
Options exercised by executives and directors (in shares)						2
Treasury stock from stock repurchases										(19,996)	(19,996)
Other comprehensive income (loss)								25			25
Cash dividends declared to stockholders									(5,759)		(5,759)
Balance at Jun. 30, 2018						$ 12	7,199	(219)	116,617	(20,746)	102,863
Balance (in shares) at Jun. 30, 2018						12,141
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									20,750		20,750
Share-based compensation							990				990
Options exercised by executives and directors							269				269
Options exercised by executives and directors (in shares)						10
Net shares repurchased for employee taxes							(256)				(256)
Net shares repurchased for employee taxes, (in shares)						(1)
Other comprehensive income (loss)								127			127
Cash dividends declared to stockholders									(8,918)		(8,918)
Balance at Mar. 31, 2019						$ 12	9,805	(46)	143,176	(30,879)	122,068
Balance (in shares) at Mar. 31, 2019						12,126
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											42,133
Net shares repurchased for employee taxes, (in shares)						(1)
Other comprehensive income (loss)											229
Balance at Jun. 30, 2019						$ 12	11,070	56	155,762	(40,877)	126,023
Balance (in shares) at Jun. 30, 2019						12,126
Balance at Mar. 31, 2019						$ 12	9,805	(46)	143,176	(30,879)	122,068
Balance (in shares) at Mar. 31, 2019						12,126
Net income									21,383		21,383
Share-based compensation							1,255				1,255
Options exercised by executives and directors							10				10
Treasury stock from stock repurchases										(9,998)	(9,998)
Other comprehensive income (loss)								102			102
Cash dividends declared to stockholders									(8,797)		(8,797)
Balance at Jun. 30, 2019						$ 12	$ 11,070	$ 56	$ 155,762	$ (40,877)	$ 126,023
Balance (in shares) at Jun. 30, 2019						12,126