Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Deferred Compensation [Member]	Accumulated Other Comprehensive Earnings (Loss) [Member]
Beginning Balance at Dec. 31, 2022	$ 1,265,737	$ 1,427	$ 677,593	$ 1,121,945	$ (11,035)	$ 11,035	$ (535,228)
Beginning Balance, Shares at Dec. 31, 2022		142,657,871
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2022					(929,210)
Net Income (Loss)	152,997			152,997
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	1,483	$ 1	1,482
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		120,535
Cash dividends declared	(75,699)			(75,699)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(104,706)						(104,706)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (623)	623
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					2,487
Stock- based compensation expense (unaudited)	3,033		3,033
Shares repurchased under stock repurchase authorization (unaudited) Value	(2,735)	$ (1)	(2,734)
Shares repurchased under stock repurchase authorization (unaudited) Shares		(101,337)
Ending Balance at Sep. 30, 2023	$ 1,240,110	$ 1,427	679,374	1,199,243	$ (11,658)	11,658	(639,934)
Ending Balance, Shares at Sep. 30, 2023		142,677,069
Treasury Stock, Ending Balance, Shares at Sep. 30, 2023	(926,723)				(926,723)
Beginning Balance at Jun. 30, 2023	$ 1,367,233	$ 1,427	680,676	1,175,410	$ (11,466)	11,466	(490,280)
Beginning Balance, Shares at Jun. 30, 2023		142,741,196
Treasury Stock, Beginning Balance, Shares at Jun. 30, 2023					(927,608)
Net Income (Loss)	49,556			49,556
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	384	$ 1	383
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		37,210
Cash dividends declared	(25,723)			(25,723)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(149,654)						(149,654)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (192)	192
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					885
Stock- based compensation expense (unaudited)	1,049		1,049
Shares repurchased under stock repurchase authorization (unaudited) Value	(2,735)	$ (1)	(2,734)
Shares repurchased under stock repurchase authorization (unaudited) Shares		(101,337)
Ending Balance at Sep. 30, 2023	$ 1,240,110	$ 1,427	679,374	1,199,243	$ (11,658)	11,658	(639,934)
Ending Balance, Shares at Sep. 30, 2023		142,677,069
Treasury Stock, Ending Balance, Shares at Sep. 30, 2023	(926,723)				(926,723)
Beginning Balance at Dec. 31, 2023	$ 1,498,900	$ 1,427	681,246	1,219,525	$ (11,855)	11,855	(403,298)
Beginning Balance, Shares at Dec. 31, 2023		142,716,939
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2023	(930,152)				(930,152)
Net Income (Loss)	$ 161,190			161,190
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	2,387	$ 2	2,385
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		189,131
Cash dividends declared	(77,201)			(77,201)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	73,481						73,481
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (798)	798
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					(1,271)
Stock- based compensation expense (unaudited)	3,434		3,434
Ending Balance at Sep. 30, 2024	$ 1,662,191	$ 1,429	687,065	1,303,514	$ (12,653)	12,653	(329,817)
Ending Balance, Shares at Sep. 30, 2024		142,906,070
Treasury Stock, Ending Balance, Shares at Sep. 30, 2024	(931,423)				(931,423)
Beginning Balance at Jun. 30, 2024	$ 1,519,026	$ 1,428	685,209	1,273,946	$ (12,378)	12,378	(441,557)
Beginning Balance, Shares at Jun. 30, 2024		142,848,909
Treasury Stock, Beginning Balance, Shares at Jun. 30, 2024					(934,135)
Net Income (Loss)	55,308			55,308
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	602	$ 1	601
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		57,161
Cash dividends declared	(25,740)			(25,740)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	111,740						111,740
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (275)	275
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					2,712
Stock- based compensation expense (unaudited)	1,255		1,255
Ending Balance at Sep. 30, 2024	$ 1,662,191	$ 1,429	$ 687,065	$ 1,303,514	$ (12,653)	$ 12,653	$ (329,817)
Ending Balance, Shares at Sep. 30, 2024		142,906,070
Treasury Stock, Ending Balance, Shares at Sep. 30, 2024	(931,423)				(931,423)