Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 234,475,000	$ 227,562,000	$ 202,034,000
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	12,762,000	13,061,000	12,793,000
Provision for credit losses	17,427,000	(1,139,000)	19,517,000
Securities premium amortization, net	70,788,000	68,308,000	41,959,000
Discount accretion on purchased loans	(1,492,000)	(2,362,000)	(3,780,000)
Gain on sale of assets, net	(4,115,000)	(1,217,000)	(4,001,000)
Deferred federal income tax (expense) benefit	(4,205,000)	3,531,000	(5,249,000)
Change in loans held-for-sale	25,194,000	44,098,000	(53,494,000)
Change in other assets	907,000	(11,308,000)	(23,233,000)
Change in other liabilities	(27,801,000)	12,697,000	24,122,000
Total adjustments	89,465,000	125,669,000	8,634,000
Net cash provided by operating activities	323,940,000	353,231,000	210,668,000
Activity in available-for-sale securities and other investments:
Sales	479,273,000	10,631,000	263,042,000
Maturities	4,132,928,000	8,495,614,000	6,075,017,000
Purchases	(4,385,683,000)	(10,887,727,000)	(7,117,151,000)
Net increase in loans held-for-investment	(1,049,925,000)	(211,786,000)	(529,144,000)
Purchases of bank premises and equipment	(15,784,000)	(19,205,000)	(16,450,000)
Proceeds from sale of bank premises and equipment and other assets	1,186,000	823,000	1,456,000
Net cash used in investing activities	(838,005,000)	(2,611,650,000)	(1,262,202,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in noninterest-bearing deposits	281,558,000	797,533,000	679,744,000
Net increase in interest-bearing deposits	157,461,000	1,093,138,000	843,142,000
Net increase (decrease) in borrowings	(28,645,000)	241,059,000	48,737,000
Common stock transactions:
Proceeds from stock option exercises	6,545,000	5,905,000	4,717,000
Dividends paid	(91,315,000)	(79,712,000)	(70,318,000)
Repurchase of stock	(9,449,000)	0	(8,008,000)
Net cash provided by financing activities	316,155,000	2,057,923,000	1,498,014,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(197,910,000)	(200,496,000)	446,480,000
CASH AND CASH EQUIVALENTS, beginning of year	528,588,000	729,084,000	282,604,000
CASH AND CASH EQUIVALENTS, end of year	330,678,000	528,588,000	729,084,000
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	30,540,000	6,198,000	14,494,000
Federal income taxes paid	45,430,000	39,528,000	44,381,000
Schedule of noncash investing and financing activities:
Assets acquired through foreclosure	0	2,711,000	164,000
Investment securities purchased but not settled	0	0	14,641,000
Restricted stock grant (forfeiture)	2,188,000	1,316,000	672,000
Stock issued in acquisition of TB&T Bancshares, Inc.	0	0	220,273,000
TB And T Bacshares Inc [Member]
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash received in acquisition, Net	$ 0	$ 0	$ 61,028,000