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, 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)	116,466			116,466
Stock option exercises (unaudited)	4,346	$ 3	4,343
Stock option exercises, Shares		234,585
Restricted stock grant/forfeiture, net (unaudited)	1,210		1,210
Restricted stock grant/forfeiture, net (unaudited), Shares		11,887
Cash dividends declared	(45,688)			(45,688)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(499,767)						(499,767)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (566)	566
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					(1,027)
Stock option expense (unaudited)	632		632
Shares repurchased under stock repurchase authorization (unaudited)	(7,405)	$ (2)	(7,403)
Shares repurchased under stock repurchase authorization (unaudited), Shares		(191,987)
Ending Balance at Jun. 30, 2022	$ 1,329,018	$ 1,426	675,653	1,052,453	$ (10,656)	10,656	(400,514)
Ending Balance, Shares at Jun. 30, 2022		142,586,601
Treasury Stock, Ending Balance, Shares at Jun. 30, 2022	(937,924)				(937,924)
Beginning Balance at Mar. 31, 2022	$ 1,488,749	$ 1,427	680,665	1,016,239	$ (10,404)	10,404	(209,582)
Beginning Balance, Shares at Mar. 31, 2022		142,704,495
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2022					(936,847)
Net earnings (Unaudited)	60,494			60,494
Stock option exercises (unaudited)	1,425	$ 1	1,424
Stock option exercises, Shares		61,834
Restricted stock grant/forfeiture, net (unaudited)	651		651
Restricted stock grant/forfeiture, net (unaudited), Shares		12,259
Cash dividends declared	(24,280)			(24,280)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(190,932)						(190,932)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (252)	252
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					(1,077)
Stock option expense (unaudited)	316		316
Shares repurchased under stock repurchase authorization (unaudited)	(7,405)	$ (2)	(7,403)
Shares repurchased under stock repurchase authorization (unaudited), Shares		(191,987)
Ending Balance at Jun. 30, 2022	$ 1,329,018	$ 1,426	675,653	1,052,453	$ (10,656)	10,656	(400,514)
Ending Balance, Shares at Jun. 30, 2022		142,586,601
Treasury Stock, Ending Balance, Shares at Jun. 30, 2022	(937,924)				(937,924)
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)	$ 103,441			103,441
Stock option exercises (unaudited)	1,128		1,128
Stock option exercises, Shares		60,095
Restricted stock grant/forfeiture, net (unaudited)	1,066		1,066
Restricted stock grant/forfeiture, net (unaudited), Shares		23,230
Cash dividends declared	(49,976)			(49,976)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	44,948						44,948
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (431)	431
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					1,602
Stock option expense (unaudited)	$ 889		889
Shares repurchased under stock repurchase authorization (unaudited), Shares	244,559
Ending Balance at Jun. 30, 2023	$ 1,367,233	$ 1,427	680,676	1,175,410	$ (11,466)	11,466	(490,280)
Ending Balance, Shares at Jun. 30, 2023		142,741,196
Treasury Stock, Ending Balance, Shares at Jun. 30, 2023	(927,608)				(927,608)
Beginning Balance at Mar. 31, 2023	$ 1,372,853	$ 1,427	679,429	1,150,246	$ (11,271)	11,271	(458,249)
Beginning Balance, Shares at Mar. 31, 2023		142,703,531
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2023					(927,789)
Net earnings (Unaudited)	50,873			50,873
Stock option exercises (unaudited)	215		215
Stock option exercises, Shares		12,475
Restricted stock grant/forfeiture, net (unaudited)	587		587
Restricted stock grant/forfeiture, net (unaudited), Shares		25,190
Cash dividends declared	(25,709)			(25,709)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(32,031)						(32,031)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (195)	195
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					181
Stock option expense (unaudited)	445		445
Ending Balance at Jun. 30, 2023	$ 1,367,233	$ 1,427	$ 680,676	$ 1,175,410	$ (11,466)	$ 11,466	$ (490,280)
Ending Balance, Shares at Jun. 30, 2023		142,741,196
Treasury Stock, Ending Balance, Shares at Jun. 30, 2023	(927,608)				(927,608)