Consolidated Statements of Shareholders' Equity - 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, 2021	$ 1,759,224	$ 1,425	$ 676,871	$ 981,675	$ (10,090)	$ 10,090	$ 99,253
Beginning Balance, Shares at Dec. 31, 2021		142,532,116
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2021					(936,897)
Net earnings (Unaudited)	55,972			55,972
Stock option exercises (unaudited)	2,921	$ 2	2,919
Stock option exercises, Shares		172,751
Restricted stock grant/forfeiture, net (unaudited)	559		559
Restricted stock grant/forfeiture, net (unaudited), Shares		(372)
Cash dividends declared	(21,408)			(21,408)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(308,835)						(308,835)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (314)	314
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					50
Stock option expense (unaudited)	316		316
Ending Balance at Mar. 31, 2022	$ 1,488,749	$ 1,427	680,665	1,016,239	$ (10,404)	10,404	(209,582)
Ending Balance, Shares at Mar. 31, 2022		142,704,495
Treasury Stock, Ending Balance, Shares at Mar. 31, 2022	(936,847)				(936,847)
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)				(929,210)
Net earnings (Unaudited)	$ 52,568			52,568
Stock option exercises (unaudited)	913		913
Stock option exercises, Shares		47,620
Restricted stock grant/forfeiture, net (unaudited)	479		479
Restricted stock grant/forfeiture, net (unaudited), Shares		(1,960)
Cash dividends declared	(24,267)			(24,267)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	76,979						76,979
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (236)	236
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					1,421
Stock option expense (unaudited)	$ 444		444
Shares repurchased under stock repurchase authorization (unaudited), Shares	244,559
Ending Balance at Mar. 31, 2023	$ 1,372,853	$ 1,427	$ 679,429	$ 1,150,246	$ (11,271)	$ 11,271	$ (458,249)
Ending Balance, Shares at Mar. 31, 2023		142,703,531
Treasury Stock, Ending Balance, Shares at Mar. 31, 2023	(927,789)				(927,789)