Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014	$ 140,175	$ 0	$ 3,000	$ 18,971	$ 117,950	$ 254
Common stock, shares outstanding at Dec. 31, 2014			16,018,734
Stockholders' Equity [Roll Forward]
Net income	21,742	0	$ 0	0	21,742	0
Total other comprehensive income (loss), net of tax	(684)	0	0	0	0	(684)
Cash dividends declared, common stock	(9,952)	0	0	0	(9,952)	0
Stock-based compensation costs	1,166	0	0	1,166	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, value	(225)	0	$ 0	(225)	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, shares			45,701
Excess tax benefits from vesting of restricted stock units	155	0	$ 0	155	0	0
Balance at Dec. 31, 2015	152,377	0	$ 3,000	20,067	129,740	(430)
Common stock, shares outstanding at Dec. 31, 2015			16,064,435
Stockholders' Equity [Roll Forward]
Net income	23,016	0	$ 0	0	23,016	0
Total other comprehensive income (loss), net of tax	(612)	0	0	0	0	(612)
Cash dividends declared, common stock	(10,800)	0	0	0	(10,800)	0
Stock-based compensation costs	1,684	0	0	1,684	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, value	(394)	0	$ 0	(394)	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, shares			73,564
Excess tax benefits from vesting of restricted stock units	105	0	$ 0	105	0	0
Balance at Dec. 31, 2016	$ 165,376	0	$ 3,000	21,462	141,956	(1,042)
Common stock, shares outstanding at Dec. 31, 2016	16,137,999		16,137,999
Stockholders' Equity [Roll Forward]
Net income	$ 23,070	0	$ 0	0	23,070	0
Total other comprehensive income (loss), net of tax	(850)	0	0	0	0	(850)
Cash dividends declared, common stock	(11,499)	0	0	0	(11,499)	0
Stock-based compensation costs	2,632	0	0	2,632	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, value	(631)	0	$ 0	(631)	0	0
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for payroll taxes, shares			77,673
Balance at Dec. 31, 2017	$ 178,098	$ 0	$ 3,000	$ 23,463	$ 153,527	$ (1,892)
Common stock, shares outstanding at Dec. 31, 2017	16,215,672		16,215,672