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, 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 and restricted stock units of common stock, net of restricted stock units withheld for payment for taxes	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					41,517
Other comprehensive income (loss), net of tax					5,130
Balance at Sep. 30, 2019	15,790	273,475	230,892	(414)	519,743
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 and restricted stock units of common stock, net of restricted stock units withheld for payment for taxes	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
Net income			15,095		15,095
Other comprehensive income (loss), net of tax				544	544
Common cash dividends declared			(944)		(944)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	6	187			193
Issuance of shares of common stock as a result of stock options exercised	12	144			156
Stock-based compensation expense		428			428
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	(1)	(28)			(29)
Balance at Sep. 30, 2019	15,790	273,475	230,892	(414)	519,743
Impact of adoption of ASU 2016-01					245,836
Balance at Dec. 31, 2019	15,828	274,785	245,836	(1,098)	535,351
Net income			11,228		11,228
Other comprehensive income (loss), net of tax				(3,691)	(3,691)
Common cash dividends declared			(942)		(942)
Repurchase and cancellation of 100,932 shares of common stock as a result of share repurchase program	(101)	(1,844)	(1,835)		(3,780)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	6	208			214
Issuance of shares of common stock as a result of stock options exercised	32	274			306
Stock-based compensation expense		641			641
Restricted stock awards and restricted stock units of common stock, net of restricted stock units withheld for payment for taxes	10	(8)			2
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised	(1)	(189)			(190)
Balance at Mar. 31, 2020	15,774	273,867	254,287	(4,789)	539,139
Balance at Dec. 31, 2019	15,828	274,785	245,836	(1,098)	535,351
Net income					42,311
Other comprehensive income (loss), net of tax					(683)
Balance at Sep. 30, 2020	15,792	275,122	283,480	(1,781)	572,613
Balance at Mar. 31, 2020	15,774	273,867	254,287	(4,789)	539,139
Net income			13,739		13,739
Other comprehensive income (loss), net of tax				3,622	3,622
Common cash dividends declared			(945)		(945)
Issuance of shares of common stock as a result of the acquisition, net of issuance cost	16	462			478
Issuance of shares of common stock as a result of stock options exercised	1	9			10
Stock-based compensation expense		423			423
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised		(446)			(446)
Balance at Jun. 30, 2020	15,791	274,315	267,081	(1,167)	556,020
Net income			17,344		17,344
Other comprehensive income (loss), net of tax				(614)	(614)
Common cash dividends declared			(945)		(945)
Issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	6	161			167
Issuance of shares of common stock as a result of stock options exercised	1	23			24
Stock-based compensation expense		472			472
Balance at Sep. 30, 2020	15,792	275,122	$ 283,480	$ (1,781)	572,613
Impact of adoption of ASU 2016-01					283,480
Exchange of shares in connection with payroll taxes for restricted stock and in connection with stock options exercised	$ 6	$ (151)			$ (145)