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 [Member]
Beginning balance at Dec. 31, 2020	$ 692,472	$ 157,784	$ 296,186	$ 306,899	$ (22,144)	$ (46,253)
Beginning balance, shares at Dec. 31, 2020		29,295,052
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	53,478			53,478
Other comprehensive income, net of income tax	2,599				2,599
Cash dividends declared	(11,741)			(11,741)
Stock-based compensation	1,643		1,700	(56)		(1)
Stock issued under dividend reinvestment and employee stock purchase plans	1,214		90	(1)		1,125
Stock issued under dividend reinvestment and employee stock purchase plans, shares		45,226
Vesting of restricted stock units	(355)		(1,126)			771
Vesting of restricted stock unit awards, shares		42,619
Exercise of stock options	983		31			952
Shares under option, exercised		(46,527)
Cancellation of performance-based restricted stock awards	0		327			(327)
Cancellation of performance-based restricted stock awards, shares		(7,199)
Purchases of treasury stock	(295)					(295)
Purchases of treasury stock, shares		(10,494)
Ending balance at Jun. 30, 2021	$ 739,998	$ 157,784	297,208	348,579	(19,545)	(44,028)
Ending balance, shares at Jun. 30, 2021		29,411,731
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.40
Beginning balance at Mar. 31, 2021	$ 722,455	$ 157,784	296,177	333,581	(20,440)	(44,647)
Beginning balance, shares at Mar. 31, 2021		29,379,575
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,875			20,875
Other comprehensive income, net of income tax	895				895
Cash dividends declared	(5,877)			(5,877)
Stock-based compensation	821		822			(1)
Stock issued under dividend reinvestment and employee stock purchase plans	605		25			580
Stock issued under dividend reinvestment and employee stock purchase plans, shares		21,915
Exercise of stock options	224		14			210
Shares under option, exercised		10,241
Cancellation of performance-based restricted stock awards	0		170			(170)
Ending balance at Jun. 30, 2021	$ 739,998	$ 157,784	297,208	348,579	(19,545)	(44,028)
Ending balance, shares at Jun. 30, 2021		29,411,731
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.20
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	33,483			33,483
Other comprehensive income, net of income tax	(26,428)				(26,428)
Cash dividends declared	(12,105)			(12,105)
Stock-based compensation	1,802		2,009	(207)
Stock issued under dividend reinvestment and employee stock purchase plans	1,275		104			1,171
Stock issued under dividend reinvestment and employee stock purchase plans, shares		47,617
Vesting of restricted stock units	(901)		(2,544)			1,643
Vesting of restricted stock unit awards, shares		91,835
Exercise of stock options	$ 575		50			525
Shares under option, exercised	25,781	25,781
Purchases of treasury stock	$ (7,570)					(7,570)
Purchases of treasury stock, shares		(300,000)
Ending balance at Jun. 30, 2022	$ 763,925	$ 157,784	298,800	396,295	(42,781)	(46,173)
Ending balance, shares at Jun. 30, 2022		29,365,775
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.41
Beginning balance at Mar. 31, 2022	$ 773,855	$ 157,784	297,945	389,332	(31,909)	(39,297)
Beginning balance, shares at Mar. 31, 2022		29,636,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,166			13,166
Other comprehensive income, net of income tax	(10,872)				(10,872)
Cash dividends declared	(6,200)			(6,200)
Stock-based compensation	933		936	(3)
Stock issued under dividend reinvestment and employee stock purchase plans	652		45			607
Stock issued under dividend reinvestment and employee stock purchase plans, shares		25,774
Vesting of restricted stock units	(38)		(126)			88
Vesting of restricted stock unit awards, shares		3,576
Exercise of stock options	(1)					(1)
Purchases of treasury stock	(7,570)					(7,570)
Purchases of treasury stock, shares		(300,000)
Ending balance at Jun. 30, 2022	$ 763,925	$ 157,784	$ 298,800	$ 396,295	$ (42,781)	$ (46,173)
Ending balance, shares at Jun. 30, 2022		29,365,775
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.21