CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2017	$ 13,918	$ 189,077	$ 151,963	$ (1,671)	$ 353,287
Net income			10,550		10,550
Other comprehensive income (loss), net of tax				(3,202)	(3,202)
Impact of adoption of ASU 2016-01 | ASU 2016-01			667	(667)
Common cash dividends declared			(834)		(834)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	3	100			103
Issuance of shares of common stock as a result of stock options exercised	13	193			206
Stock-based compensation expense		496			496
Restricted stock awards - shares of common stock	7	(7)
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	(4)	(174)			(178)
Balance at Mar. 31, 2018	13,937	189,685	162,346	(5,540)	360,428
Balance at Dec. 31, 2017	13,918	189,077	151,963	(1,671)	353,287
Net income					20,995
Other comprehensive income (loss), net of tax					(4,536)
Balance at Jun. 30, 2018	13,974	190,533	171,955	(6,874)	369,588
Balance at Mar. 31, 2018	13,937	189,685	162,346	(5,540)	360,428
Net income			10,445		10,445
Other comprehensive income (loss), net of tax				(1,334)	(1,334)
Common cash dividends declared			(836)		(836)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	6	215			221
Issuance of shares of common stock as a result of stock options exercised	26	362			388
Stock-based compensation expense		292			292
Restricted stock awards - shares of common stock	4	(4)
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	1	(17)			(16)
Balance at Jun. 30, 2018	13,974	190,533	171,955	(6,874)	369,588
Balance at Dec. 31, 2018	15,718	270,761	192,203	(5,544)	473,138
Net income			12,918		12,918
Other comprehensive income (loss), net of tax				2,344	2,344
Common cash dividends declared			(942)		(942)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	4	124			128
Issuance of shares of common stock as a result of stock options exercised	25	263			288
Stock-based compensation expense		722			722
Restricted stock awards - shares of common stock	13	(50)			(37)
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	(5)	(147)			(152)
Balance at Mar. 31, 2019	15,755	271,673	204,179	(3,200)	488,407
Balance at Dec. 31, 2018	15,718	270,761	192,203	(5,544)	473,138
Net income					26,422
Other comprehensive income (loss), net of tax					4,586
Balance at Jun. 30, 2019	15,773	272,744	216,741	(958)	504,300
Balance at Mar. 31, 2019	15,755	271,673	204,179	(3,200)	488,407
Net income			13,504		13,504
Other comprehensive income (loss), net of tax				2,242	2,242
Common cash dividends declared			(942)		(942)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	11	323			334
Issuance of shares of common stock as a result of stock options exercised	3	41			44
Stock-based compensation expense		719			719
Restricted stock awards - shares of common stock	5	(5)
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	(1)	(7)			(8)
Balance at Jun. 30, 2019	$ 15,773	$ 272,744	$ 216,741	$ (958)	$ 504,300