Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Capital Stock [Member]	Surplus [Member]	Undivided Profits [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Total	Cumulative Effect, Period of Adoption, Adjustment [Member] Undivided Profits [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Capital Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Surplus [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Undivided Profits [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Accumulated Other Comprehensive Loss [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Balance at Dec. 31, 2021	$ 20,046	$ 256,661	$ 349,056	$ 12,147	$ (36,782)	$ 601,128	$ (3,470)	$ (3,470)	$ 20,046	$ 256,661	$ 345,586	$ 12,147	$ (36,782)	$ 597,658
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible Enumeration]							ASU 2016-13 [Member]				ASU 2016-13 [Member]
Net income	0	0	17,089	0	0	17,089
Other comprehensive (loss) income, net of tax	0	0	0	(14,516)	0	(14,516)
Cash dividend declared	0	0	(6,727)	0	0	(6,727)
Purchase of treasury stock	0	0	0	0	(609)	(609)
Balance at Mar. 31, 2022	20,046	256,661	355,948	(2,369)	(37,391)	592,895
Balance at Dec. 31, 2021	20,046	256,661	349,056	12,147	(36,782)	601,128	$ (3,470)	$ (3,470)	$ 20,046	$ 256,661	$ 345,586	$ 12,147	$ (36,782)	$ 597,658
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						54,324
Other comprehensive (loss) income, net of tax						(37,356)
Balance at Sep. 30, 2022	20,046	256,661	379,769	(25,209)	(42,261)	589,006
Balance at Mar. 31, 2022	20,046	256,661	355,948	(2,369)	(37,391)	592,895
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	17,871	0	0	17,871
Other comprehensive (loss) income, net of tax	0	0	0	(7,053)	0	(7,053)
Cash dividend declared	0	0	(6,719)	0	0	(6,719)
Purchase of treasury stock	0	0	0	0	(2,362)	(2,362)
Balance at Jun. 30, 2022	20,046	256,661	367,100	(9,422)	(39,753)	594,632
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	19,364	0	0	19,364
Other comprehensive (loss) income, net of tax	0	0	0	(15,787)	0	(15,787)
Cash dividend declared	0	0	(6,695)	0	0	(6,695)
Purchase of treasury stock	0	0	0	0	(2,508)	(2,508)
Balance at Sep. 30, 2022	20,046	256,661	379,769	(25,209)	(42,261)	589,006
Balance at Dec. 31, 2022	20,058	257,078	393,831	(27,194)	(43,786)	599,987
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	17,746	0	0	17,746
Other comprehensive (loss) income, net of tax	0	0	0	3,819	0	3,819
Cash dividend declared	0	0	(6,849)	0	0	(6,849)
Balance at Mar. 31, 2023	20,058	257,078	404,728	(23,375)	(43,786)	614,703
Balance at Dec. 31, 2022	20,058	257,078	393,831	(27,194)	(43,786)	599,987
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						48,798
Other comprehensive (loss) income, net of tax						(4,312)
Balance at Sep. 30, 2023	20,058	257,078	422,082	(31,506)	(43,786)	623,926
Balance at Mar. 31, 2023	20,058	257,078	404,728	(23,375)	(43,786)	614,703
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	16,372	0	0	16,372
Other comprehensive (loss) income, net of tax	0	0	0	(2,837)	0	(2,837)
Cash dividend declared	0	0	(6,849)	0	0	(6,849)
Balance at Jun. 30, 2023	20,058	257,078	414,251	(26,212)	(43,786)	621,389
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	14,680	0	0	14,680
Other comprehensive (loss) income, net of tax	0	0	0	(5,294)	0	(5,294)
Cash dividend declared	0	0	(6,849)	0	0	(6,849)
Balance at Sep. 30, 2023	$ 20,058	$ 257,078	$ 422,082	$ (31,506)	$ (43,786)	$ 623,926