Condensed Financial Information - Parent Company - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net earnings		$ 198,977	$ 234,475	$ 227,562
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization		12,578	12,762	13,061
Decrease (increase) in other assets		(3,895)	(1,281)	(11,317)
Increase (decrease) in other liabilities		6,663	(29,577)	10,953
Cash flows from investing activities:
Purchases of bank premises and equipment and software		(17,251)	(15,784)	(19,205)
Cash flows from financing activities:
Cash dividends paid		(99,965)	(91,315)	(79,712)
Repurchase of stock		(2,736)	(9,449)	0
Net increase in cash and cash equivalents		205,913	(197,910)	(200,496)
Cash and cash equivalents, beginning of year		330,678
Cash and cash equivalents, end of year		536,591	330,678
Parent Company [Member]
Cash flows from operating activities:
Net earnings		198,977	234,475	227,562
Adjustments to reconcile net earnings to net cash provided by operating activities:
Excess of earnings over dividends of subsidiaries (1)	[1]	(72,444)	(174,741)	(140,441)
Depreciation and amortization		116	188	189
Decrease (increase) in other assets		698	645	(693)
Increase (decrease) in other liabilities		(2,721)	933	2,997
Other		2	0	(4)
Net cash provided by operating activities		124,628	61,500	89,610
Cash flows from investing activities:
Purchases of bank premises and equipment and software		0	(385)	(106)
Net cash provided by (used in) investing activities		0	(385)	(106)
Cash flows from financing activities:
Proceeds from stock option exercises		2,132	6,545	5,905
Cash dividends paid		(99,965)	(91,315)	(79,712)
Repurchase of stock		(2,735)	(9,449)	0
Net cash used in financing activities		(100,568)	(94,219)	(73,807)
Net increase in cash and cash equivalents		24,060	(33,104)	15,697
Cash and cash equivalents, beginning of year		119,259	152,363	136,666
Cash and cash equivalents, end of year		$ 143,319	$ 119,259	$ 152,363

[1] Eliminates in consolidation