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 earnings (Unaudited)	103,441			103,441
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	1,098		1,098
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		83,325
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- based compensation expense (unaudited)	1,985		1,985
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/ stock unit conversions/ restricted stock activity (unaudited)	215		215
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		37,665
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- based compensation expense (unaudited)	1,032		1,032
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 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 earnings (Unaudited)	$ 105,882			105,882
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	1,785	$ 1	1,784
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		131,970
Cash dividends declared	(51,461)			(51,461)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(38,259)						(38,259)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (523)	523
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					(3,983)
Stock- based compensation expense (unaudited)	2,179		2,179
Ending Balance at Jun. 30, 2024	$ 1,519,026	$ 1,428	685,209	1,273,946	$ (12,378)	12,378	(441,557)
Ending Balance, Shares at Jun. 30, 2024		142,848,909
Treasury Stock, Ending Balance, Shares at Jun. 30, 2024	(934,135)				(934,135)
Beginning Balance at Mar. 31, 2024	$ 1,491,367	$ 1,428	683,997	1,247,169	$ (12,120)	12,120	(441,227)
Beginning Balance, Shares at Mar. 31, 2024		142,817,159
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2024					(931,427)
Net earnings (Unaudited)	52,485			52,485
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited)	162		162
Stock option exercises/ stock unit conversions/ restricted stock activity (unaudited), Shares		31,750
Cash dividends declared	(25,708)			(25,708)
Change in unrealized gain (loss) in investment securities available-for-sale, net of related income taxes (unaudited)	(330)						(330)
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)					$ (258)	258
Shares purchased in connection with directors' deferred compensation plan, net (unaudited), Shares					(2,708)
Stock- based compensation expense (unaudited)	1,050		1,050
Ending Balance at Jun. 30, 2024	$ 1,519,026	$ 1,428	$ 685,209	$ 1,273,946	$ (12,378)	$ 12,378	$ (441,557)
Ending Balance, Shares at Jun. 30, 2024		142,848,909
Treasury Stock, Ending Balance, Shares at Jun. 30, 2024	(934,135)				(934,135)