Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 55,972,000	$ 56,918,000
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	3,231,000	3,171,000
Provision for Credit losses	4,782,000	(1,997,000)
Securities premium amortization, net	19,836,000	14,105,000
Discount accretion on purchased loans	(373,000)	(591,000)
Gain on sale of assets, net	(1,074,000)	(910,000)
Change in loans held-for-sale	9,367,000	16,365,000
Change in other assets	9,434,000	8,868,000
Change in other liabilities	(14,490,000)	840,000
Total adjustments	30,713,000	39,851,000
Net cash provided by operating activities	86,685,000	96,769,000
Activity in available-for-sale securities:
Sales	0	10,631,000
Maturities	211,266,000	7,839,968,000
Purchases	(551,559,000)	(8,280,926,000)
Net increase in loans held-for-investment	(176,350,000)	(148,615,000)
Purchases of bank premises and equipment	(3,193,000)	(3,322,000)
Proceeds from sale of bank premises and equipment and other assets	0	420,000
Net cash used in investing activities	(519,836,000)	(581,844,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in noninterest-bearing deposits	198,494,000	367,448,000
Net increase in interest-bearing deposits	234,843,000	370,182,000
Net increase in borrowings	87,443,000	118,511,000
Common stock transactions:
Proceeds from stock option exercises	2,921,000	1,904,000
Dividends paid	(21,385,000)	(18,483,000)
Net cash provided by financing activities	502,316,000	839,562,000
NET INCREASE IN CASH AND CASH EQUIVALENTS	69,165,000	354,487,000
CASH AND CASH EQUIVALENTS, beginning of period	528,588,000	729,084,000
CASH AND CASH EQUIVALENTS, end of period	597,753,000	1,083,571,000
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	1,523,000	1,843,000
Transfer of loans to other real estate	0	255,000
Investment securities purchased but not settled	0	381,871,000
Restricted stock grant (forfeiture)	$ 559,000	$ (17,000)