CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Common stock, shares outstanding at Dec. 31, 2019		17,363,000
Shareholders' equity at Dec. 31, 2019	$ 503,492	$ 1,085	$ 123,281	$ 390,363	$ (11,237)	$ 0
Shareholders' equity (Accounting Standards Update 2016-13) at Dec. 31, 2019	(6,108)			(6,108)
Net income	32,941			32,941
Total other comprehensive income (loss), net of tax	10,775				10,775
Cash dividends declared	(17,810)			(17,810)
Share-based compensation	1,613		1,613
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, shares		22,000
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, value	(418)	$ 0	(1,210)			792
Treasury stock purchased under 2019 Stock Repurchase Program, shares acquired		(125,000)
Treasury stock purchased under 2019 Stock Repurchase Program, amount acquired	(4,322)					(4,322)
Common stock, shares outstanding at Jun. 30, 2020		17,260,000
Shareholders' equity at Jun. 30, 2020	520,163	$ 1,085	123,684	399,386	(462)	(3,530)
Common stock, shares outstanding at Mar. 31, 2020		17,252,000
Shareholders' equity at Mar. 31, 2020	508,597	$ 1,085	123,167	387,243	929	(3,827)
Net income	21,040			21,040
Total other comprehensive income (loss), net of tax	(1,391)				(1,391)
Cash dividends declared	(8,897)			(8,897)
Share-based compensation	855		855
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, shares		8,000
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, value	(41)	$ 0	(338)			297
Common stock, shares outstanding at Jun. 30, 2020		17,260,000
Shareholders' equity at Jun. 30, 2020	$ 520,163	$ 1,085	123,684	399,386	(462)	(3,530)
Common stock, shares outstanding at Dec. 31, 2020	17,265,337	17,265,000
Shareholders' equity at Dec. 31, 2020	$ 534,195	$ 1,085	125,610	418,246	(7,391)	(3,355)
Net income	37,931			37,931
Total other comprehensive income (loss), net of tax	(7,737)				(7,737)
Cash dividends declared	(18,250)			(18,250)
Share-based compensation	1,882		1,882
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, shares		55,000
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, value	$ (165)	$ 0	(2,050)			1,885
Common stock, shares outstanding at Jun. 30, 2021	17,320,446	17,320,000
Shareholders' equity at Jun. 30, 2021	$ 547,856	$ 1,085	125,442	437,927	(15,128)	(1,470)
Common stock, shares outstanding at Mar. 31, 2021		17,306,000
Shareholders' equity at Mar. 31, 2021	533,599	$ 1,085	124,882	429,598	(20,006)	(1,960)
Net income	17,460			17,460
Total other comprehensive income (loss), net of tax	4,878				4,878
Cash dividends declared	(9,131)			(9,131)
Share-based compensation	964		964
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, shares		14,000
Exercise of stock options and issuance of other compensation-related equity awards, net of awards surrendered, value	$ 86	$ 0	(404)			490
Common stock, shares outstanding at Jun. 30, 2021	17,320,446	17,320,000
Shareholders' equity at Jun. 30, 2021	$ 547,856	$ 1,085	$ 125,442	$ 437,927	$ (15,128)	$ (1,470)