Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 56,918	$ 37,232
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	3,171	3,087
Provision for credit losses	(1,997)	9,850
Securities premium amortization, net	14,105	7,239
Discount accretion on purchased loans	(591)	(354)
Gain on sale of assets, net	(910)	(2,250)
Change in loans held-for-sale	16,365	(13,445)
Change in other assets	8,868	(15,046)
Change in other liabilities	840	4,919
Total adjustments	39,851	(6,000)
Net cash provided by operating activities	96,769	31,232
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash received in acquisition of TB&T Bancshares, Inc.		61,028
Activity in available-for-sale securities:
Sales	10,631	95,437
Maturities	7,839,968	1,614,414
Purchases	(8,280,926)	(2,333,332)
Net (increase) decrease in loans held-for-investment	(148,615)	1,366
Purchases of bank premises and equipment	(3,322)	(5,734)
Proceeds from sale of bank premises and equipment and other assets	420	171
Net cash used in investing activities	(581,844)	(566,650)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	367,448	(14,356)
Net increase in interest-bearing deposits	370,182	72,633
Net increase in borrowings	118,511	476,515
Common stock transactions:
Proceeds from stock option exercises	1,904	2,192
Dividends paid	(18,483)	(16,306)
Net cash provided by financing activities	839,562	520,678
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	354,487	(14,740)
CASH AND CASH EQUIVALENTS, beginning of period	729,084	282,604
CASH AND CASH EQUIVALENTS, end of period	1,083,571	267,864
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	1,843	7,042
Transfer of loans and bank premises to other real estate	255
Investment securities purchased but not settled	381,871	33,066
Investment securities sold but not yet settled		126,119
Restricted stock grant (forfeiture) to officers and directors	$ (17)	118
Stock issued in acquisition of TB&T Bancshares, Inc.		$ 220,273