Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Surplus	Retained Earnings	Other Comprehensive Income (Loss)	Treasury Stock	Total
Balance at Dec. 31, 2022	$ 96,420	$ 154,061	$ 2,695,567	$ (470,497)	$ (430,792)	$ 2,044,759
Balance (in shares) at Dec. 31, 2022	96,420
Increase (decrease) in shareholders' equity
Net Income (Loss)			305,392			305,392
Dividends:
Dividends Payable/ Cash			(78,247)			(78,247)
Purchase of treasury stock					(4,487)	(4,487)
Exercise of stock options	$ 24	630				654
Exercise of stock options (in shares)	24
Stock compensation expense recognized in earnings		255				255
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments				(74,715)		(74,715)
Balance at Sep. 30, 2023	$ 96,444	154,946	2,922,712	(545,212)	(435,279)	2,193,611
Balance (in shares) at Sep. 30, 2023	96,444
Balance at Jun. 30, 2023	$ 96,432	154,522	2,858,544	(482,312)	(435,195)	2,191,991
Balance (in shares) at Jun. 30, 2023	96,432
Increase (decrease) in shareholders' equity
Net Income (Loss)			103,264			103,264
Dividends:
Dividends Payable/ Cash			(39,096)			(39,096)
Purchase of treasury stock					(84)	(84)
Exercise of stock options	$ 12	348				360
Exercise of stock options (in shares)	12
Stock compensation expense recognized in earnings		76				76
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments				(62,900)		(62,900)
Balance at Sep. 30, 2023	$ 96,444	154,946	2,922,712	(545,212)	(435,279)	2,193,611
Balance (in shares) at Sep. 30, 2023	96,444
Balance at Dec. 31, 2023	$ 96,467	155,511	3,029,088	(397,889)	(435,403)	2,447,774
Balance (in shares) at Dec. 31, 2023	96,467
Increase (decrease) in shareholders' equity
Net Income (Loss)			294,083			294,083
Dividends:
Dividends Payable/ Cash			(82,078)			(82,078)
Purchase of treasury stock					(742)	(742)
Exercise of stock options	$ 136	3,160				3,296
Exercise of stock options (in shares)	136
Stock compensation expense recognized in earnings		169				169
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments				86,914		86,914
Balance at Sep. 30, 2024	$ 96,603	158,840	3,241,093	(310,975)	(436,145)	2,749,416
Balance (in shares) at Sep. 30, 2024	96,603
Balance at Jun. 30, 2024	$ 96,580	158,171	3,182,368	(423,860)	(435,898)	2,577,361
Balance (in shares) at Jun. 30, 2024	96,580
Increase (decrease) in shareholders' equity
Net Income (Loss)			99,772			99,772
Dividends:
Dividends Payable/ Cash			(41,047)			(41,047)
Purchase of treasury stock					(247)	(247)
Exercise of stock options	$ 23	622				645
Exercise of stock options (in shares)	23
Stock compensation expense recognized in earnings		47				47
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments				112,885		112,885
Balance at Sep. 30, 2024	$ 96,603	$ 158,840	$ 3,241,093	$ (310,975)	$ (436,145)	$ 2,749,416
Balance (in shares) at Sep. 30, 2024	96,603