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
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 income (loss), 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						34,118
Other comprehensive income (loss), net of tax						982
Balance at Jun. 30, 2023	20,058	257,078	414,251	(26,212)	(43,786)	621,389
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 income (loss), 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
Balance at Dec. 31, 2023	20,058	257,181	425,069	(13,237)	(43,786)	645,285
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	12,126	0	0	12,126
Other comprehensive income (loss), net of tax	0	0	0	(1,526)	0	(1,526)
Cash dividend declared	0	0	(6,849)	0	0	(6,849)
Stock based compensation expense	0	154	0	0	0	154
Balance at Mar. 31, 2024	20,058	257,335	430,346	(14,763)	(43,786)	649,190
Balance at Dec. 31, 2023	20,058	257,181	425,069	(13,237)	(43,786)	645,285
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						24,677
Other comprehensive income (loss), net of tax						(1,031)
Balance at Jun. 30, 2024	20,058	257,490	436,048	(14,268)	(44,160)	655,168
Balance at Mar. 31, 2024	20,058	257,335	430,346	(14,763)	(43,786)	649,190
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	12,551	0	0	12,551
Other comprehensive income (loss), net of tax	0	0	0	495	0	495
Cash dividend declared	0	0	(6,849)	0	0	(6,849)
Purchase of treasury stock	0	0	0	0	(374)	(374)
Stock based compensation expense	0	155	0	0	0	155
Balance at Jun. 30, 2024	$ 20,058	$ 257,490	$ 436,048	$ (14,268)	$ (44,160)	$ 655,168