Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock, Common
Beginning balance at Dec. 31, 2021	$ 773,794	$ 157,784	$ 299,181	$ 375,124	$ (16,353)	$ (41,942)
Beginning balance, shares at Dec. 31, 2021		29,500,542
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,284			54,284
Other comprehensive income, net of income tax	(48,632)				(48,632)
Cash dividends declared	(18,258)			(18,258)
Stock-based compensation	2,774		2,982	(208)		0
Stock issued under dividend reinvestment and employee stock purchase plans	1,934		129	0		1,805
Stock issued under dividend reinvestment and employee stock purchase plans, shares		74,055
Vesting of restricted stock units, net of shares withheld to cover taxes	(903)		(2,551)			1,648
Vesting of restricted stock unit awards, shares		92,073
Exercise of stock options	575		50			525
Shares under option, exercised		25,781
Purchases of treasury stock	(11,381)					(11,381)
Purchases of treasury stock, shares		(450,000)
Ending balance at Sep. 30, 2022	$ 754,187	$ 157,784	299,791	410,942	(64,985)	(49,345)
Ending balance, shares at Sep. 30, 2022		29,242,451
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.62
Beginning balance at Jun. 30, 2022	$ 763,925	$ 157,784	298,800	396,295	(42,781)	(46,173)
Beginning balance, shares at Jun. 30, 2022		29,365,775
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,801			20,801
Other comprehensive income, net of income tax	(22,204)				(22,204)
Cash dividends declared	(6,153)			(6,153)
Stock-based compensation	972		973	(1)		0
Stock issued under dividend reinvestment and employee stock purchase plans	659		25			634
Stock issued under dividend reinvestment and employee stock purchase plans, shares		26,438
Vesting of restricted stock units, net of shares withheld to cover taxes	(2)		(7)			5
Vesting of restricted stock unit awards, shares		238
Purchases of treasury stock	(3,811)					(3,811)
Purchases of treasury stock, shares		(150,000)
Ending balance at Sep. 30, 2022	$ 754,187	$ 157,784	299,791	410,942	(64,985)	(49,345)
Ending balance, shares at Sep. 30, 2022		29,242,451
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.21
Beginning balance at Dec. 31, 2022	$ 776,500	$ 157,784	300,808	428,637	(62,104)	(48,625)
Beginning balance, shares at Dec. 31, 2022		29,271,915
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,850			54,850
Other comprehensive income, net of income tax	(9,482)				(9,482)
Cash dividends declared	(18,521)			(18,521)
Stock-based compensation	2,990		3,322	(332)
Stock issued under dividend reinvestment and employee stock purchase plans	1,979		(84)			2,063
Stock issued under dividend reinvestment and employee stock purchase plans, shares		98,402
Vesting of restricted stock units, net of shares withheld to cover taxes	(1,232)		(3,857)			2,625
Vesting of restricted stock unit awards, shares		131,601
Exercise of stock options	$ 114		(18)			132
Shares under option, exercised	6,210	6,210
Ending balance at Sep. 30, 2023	$ 807,198	$ 157,784	300,171	464,634	(71,586)	(43,805)
Ending balance, shares at Sep. 30, 2023		29,508,128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.63
Beginning balance at Jun. 30, 2023	$ 805,222	$ 157,784	299,212	453,806	(61,034)	(44,546)
Beginning balance, shares at Jun. 30, 2023		29,471,124
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,016			17,016
Other comprehensive income, net of income tax	(10,552)				(10,552)
Cash dividends declared	(6,190)			(6,190)
Stock-based compensation	1,033		1,031	2
Stock issued under dividend reinvestment and employee stock purchase plans	670		(65)			735
Stock issued under dividend reinvestment and employee stock purchase plans, shares		36,766
Vesting of restricted stock units, net of shares withheld to cover taxes	(1)		(7)			6
Vesting of restricted stock unit awards, shares		238
Ending balance at Sep. 30, 2023	$ 807,198	$ 157,784	$ 300,171	$ 464,634	$ (71,586)	$ (43,805)
Ending balance, shares at Sep. 30, 2023		29,508,128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.21