Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2020	$ 701,106	$ 47,619	$ 171,304	$ 589,988	$ (139,038)	$ 31,233
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,962			41,962
Other comprehensive income (loss)	(8,667)					(8,667)
Cash dividends declared	(18,397)			(18,397)
Stock-based compensation expense	1,778		1,778
Restricted awards granted	0		(1,860)		1,860
Exercise of stock options	537		(1,548)		2,085
Purchase of treasury shares	(22,843)				(22,843)
Ending balance at Jun. 30, 2021	$ 695,476	47,619	169,674	613,553	(157,936)	22,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	11,690
Beginning Balance at Mar. 31, 2021	$ 691,685	47,619	170,526	600,396	(142,484)	15,628
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,148			22,148
Other comprehensive income (loss)	6,938					6,938
Cash dividends declared	(8,991)			(8,991)
Stock-based compensation expense	625		625
Restricted awards granted	0		(1,396)		1,396
Exercise of stock options	152		(81)		233
Purchase of treasury shares	(17,081)				(17,081)
Ending balance at Jun. 30, 2021	$ 695,476	47,619	169,674	613,553	(157,936)	22,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	2,921
Beginning Balance at Dec. 31, 2021	$ 681,105	47,619	170,942	641,826	(193,542)	14,260
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,025			44,025
Other comprehensive income (loss)	(98,243)					(98,243)
Cash dividends declared	(17,918)			(17,918)
Stock-based compensation expense	1,658		1,658
Restricted awards granted	0		(2,658)		2,658
Exercise of stock options	661		(385)		1,046
Purchase of treasury shares	(19,295)				(19,295)
Ending balance at Jun. 30, 2022	$ 591,993	47,619	169,557	667,933	(209,133)	(83,983)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	13,078
Beginning Balance at Mar. 31, 2022	$ 632,430	47,619	170,206	654,138	(194,819)	(44,714)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,683			22,683
Other comprehensive income (loss)	(39,269)					(39,269)
Cash dividends declared	(8,888)			(8,888)
Stock-based compensation expense	687		687
Restricted awards granted	0		(951)		951
Exercise of stock options	661		(385)		1,046
Purchase of treasury shares	(16,311)				(16,311)
Ending balance at Jun. 30, 2022	$ 591,993	$ 47,619	$ 169,557	$ 667,933	$ (209,133)	$ (83,983)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	13,078