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, 2020	$ 1,678,190	$ 1,422	$ 669,644	$ 836,729	$ (9,126)	$ 9,126	$ 170,395
Beginning Balance, Shares at Dec. 31, 2020		142,161,834
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2020					938,591
Net earnings (Unaudited)	56,918			56,918
Stock option exercises (unaudited)	1,904	$ 1	1,903
Stock option exercises, Shares		124,524
Restricted stock grant/forfeiture, net (unaudited)	(17)		(17)
Restricted stock grant/forfeiture, net (unaudited), Shares		(747)
Cash dividends declared	(18,500)			18,500
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(53,386)						(53,386)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ 259	(259)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					587
Stock option expense (unaudited)	319		319
Ending Balance at Mar. 31, 2021	$ 1,665,428	$ 1,423	671,849	875,147	$ (9,385)	9,385	117,009
Ending Balance, Shares at Mar. 31, 2021		142,285,611
Treasury Stock, Ending Balance, Shares at Mar. 31, 2021	(938,004)				938,004
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)				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