Consolidated Statements of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		6,872,000
Beginning balance, value at Dec. 31, 2017	$ 192,802	$ 6,872	$ 61,793	$ 124,407	$ (270)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(1,664)			(1,664)
Stock-based compensation expense	253		253
Other comprehensive income (loss), net of tax	(418)				(418)
Net income	4,062			4,062
Ending balance (in shares) at Mar. 31, 2018		6,872,000
Ending balance, value at Mar. 31, 2018	194,973	$ 6,872	62,046	126,934	(879)
Beginning balance (in shares) at Dec. 31, 2017		6,872,000
Beginning balance, value at Dec. 31, 2017	$ 192,802	$ 6,872	61,793	124,407	(270)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock units, net (in shares)	996
Other comprehensive income (loss), net of tax	$ (240)
Net income	9,892
Ending balance (in shares) at Jun. 30, 2018		6,873,000
Ending balance, value at Jun. 30, 2018	199,456	$ 6,873	62,187	131,097	(701)
Beginning balance (in shares) at Mar. 31, 2018		6,872,000
Beginning balance, value at Mar. 31, 2018	194,973	$ 6,872	62,046	126,934	(879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(1,667)			(1,667)
Stock-based compensation expense	$ 159		159
Exercise of stock options and vesting of restricted stock units, net (in shares)	996	1,000
Exercise of stock options and vesting of restricted stock units, net	$ (17)	$ 1	(18)
Other comprehensive income (loss), net of tax	178				178
Net income	5,830			5,830
Ending balance (in shares) at Jun. 30, 2018		6,873,000
Ending balance, value at Jun. 30, 2018	199,456	$ 6,873	62,187	131,097	(701)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(1,874)			(1,874)
Stock-based compensation expense	159		159
Exercise of stock options and vesting of restricted stock units, net (in shares)		11,000
Exercise of stock options and vesting of restricted stock units, net	177	$ 11	166
Other comprehensive income (loss), net of tax	60				60
Net income	5,264			5,264
Ending balance (in shares) at Sep. 30, 2018		6,884,000
Ending balance, value at Sep. 30, 2018	203,242	$ 6,884	62,512	134,487	(641)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(1,883)			(1,883)
Stock-based compensation expense	245		245
Exercise of stock options and vesting of restricted stock units, net (in shares)		15,000
Exercise of stock options and vesting of restricted stock units, net	(132)	$ 15	(147)
Repurchase of common stock (in shares)		(16,000)
Repurchase of common stock	(494)	$ (16)	(478)
Other comprehensive income (loss), net of tax	121				121
Net income	$ 4,848			4,848
Ending balance (in shares) at Dec. 31, 2018	6,883,216	6,883,000
Ending balance, value at Dec. 31, 2018	$ 205,947	$ 6,883	62,132	137,452	(520)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(2,087)			(2,087)
Stock-based compensation expense	196		196
Exercise of stock options and vesting of restricted stock units, net (in shares)		2,000
Exercise of stock options and vesting of restricted stock units, net	0	$ 2	(2)
Repurchase of common stock (in shares)		(6,000)
Repurchase of common stock	(205)	$ (6)	(199)
Other comprehensive income (loss), net of tax	675				675
Net income	4,312			4,312
Ending balance (in shares) at Mar. 31, 2019		6,879,000
Ending balance, value at Mar. 31, 2019	$ 208,838	$ 6,879	62,127	139,677	155
Beginning balance (in shares) at Dec. 31, 2018	6,883,216	6,883,000
Beginning balance, value at Dec. 31, 2018	$ 205,947	$ 6,883	62,132	137,452	(520)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of restricted stock units, net (in shares)	1,723
Other comprehensive income (loss), net of tax	$ 1,017
Net income	$ 8,573
Ending balance (in shares) at Jun. 30, 2019	6,729,456	6,729,000
Ending balance, value at Jun. 30, 2019	$ 206,338	$ 6,729	57,234	141,878	497
Beginning balance (in shares) at Mar. 31, 2019		6,879,000
Beginning balance, value at Mar. 31, 2019	208,838	$ 6,879	62,127	139,677	155
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(2,060)			(2,060)
Stock-based compensation expense	$ 155		155
Exercise of stock options and vesting of restricted stock units, net (in shares)	0
Repurchase of common stock (in shares)		(150,000)
Repurchase of common stock	$ (5,198)	$ (150)	(5,048)
Other comprehensive income (loss), net of tax	342				342
Net income	$ 4,261			4,261
Ending balance (in shares) at Jun. 30, 2019	6,729,456	6,729,000
Ending balance, value at Jun. 30, 2019	$ 206,338	$ 6,729	$ 57,234	$ 141,878	$ 497