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, 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)
Repurchase and cancellation of shares of common stock as a result of share repurchase program	(101)	(1,844)	(1,835)		(3,780)
Common cash dividends declared			(942)		(942)
Stock-based compensation expense		641			641
Issuance of common stock under employee benefit plans	47	285			332
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)
Stock-based compensation expense		423			423
Issuance of common stock under employee benefit plans	17	25			42
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)
Stock-based compensation expense		472			472
Issuance of common stock under employee benefit plans	1	335			336
Balance at Sep. 30, 2020	15,792	275,122	283,480	(1,781)	572,613
Impact of adoption of ASU 2016-13					300,804
Balance at Dec. 31, 2020	15,806	275,807	300,804	1,376	593,793
Net income			17,982		17,982
Other comprehensive income (loss), net of tax				(1,751)	(1,751)
Common cash dividends declared			(949)		(949)
Stock-based compensation expense		841			841
Issuance of common stock under employee benefit plans		(298)			(260)
Issuance of common stock under employee benefit plans	38
Balance at Mar. 31, 2021	15,844	276,350	316,900	(375)	608,719
Balance at Dec. 31, 2020	15,806	275,807	300,804	1,376	593,793
Net income					71,896
Other comprehensive income (loss), net of tax					(118)
Balance at Sep. 30, 2021	15,590	272,964	360,003	1,257	649,814
Impact of adoption of ASU 2016-13 | Accounting Standards Update 2016-13			937		937
Balance at Mar. 31, 2021	15,844	276,350	316,900	(375)	608,719
Net income			22,349		22,349
Other comprehensive income (loss), net of tax				4,179	4,179
Repurchase and cancellation of shares of common stock as a result of share repurchase program	(100)	(1,826)	(2,874)		(4,800)
Common cash dividends declared			(951)		(951)
Stock-based compensation expense		520			520
Issuance of common stock under employee benefit plans	20	440			460
Balance at Jun. 30, 2021	15,764	275,485	335,424	3,803	630,476
Net income			31,565		31,565
Other comprehensive income (loss), net of tax				(2,546)	(2,546)
Repurchase and cancellation of shares of common stock as a result of share repurchase program	(193)	(3,134)	(6,040)		(9,367)
Common cash dividends declared			(946)		(946)
Stock-based compensation expense		504			504
Issuance of common stock under employee benefit plans	19	109			128
Balance at Sep. 30, 2021	$ 15,590	$ 272,964	$ 360,003	$ 1,257	649,814
Impact of adoption of ASU 2016-13					$ 360,003