CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 55,924	$ 47,958	$ 170,343	$ 98,129
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			20,342	20,726
Provision (benefit) for credit losses			(12,262)	49,994
Net amortization of premium on securities			30,975	9,925
Securities gains, net	(1,535)	(1,300)	(4,347)	(4,964)
Unrealized gain on equity securities, net			(85)	(604)
Stock based compensation			6,732	5,551
Loans originated for sale			(364,808)	(461,723)
Proceeds on sales of loans held for sale			401,078	443,913
Net gains on sale of loans held for sale			(15,399)	(21,411)
(Increase) decrease in accrued interest receivable			353	(7,955)
Decrease in prepaid expenses			318	408
Decrease in accrued interest payable			(271)	(1,461)
Capitalization of servicing rights			(1,055)	(2,633)
Valuation adjustment on servicing rights	(195)	120	(586)	1,676
Loss on sales/valuations of assets, net			1,970	2,480
Net excess tax benefit (expense) from stock based compensation			304	(93)
Other, net			(751)	(48,914)
NET CASH PROVIDED BY OPERATING ACTIVITIES			232,851	83,044
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of time deposits in other financial institutions			(9)	(8)
Proceeds from the sale of securities available for sale	169,108	306,383	799,588	818,022
Proceeds from the sale of securities held to maturity			0	1,056
Proceeds from the maturity of and principal paydowns on securities available for sale			722,512	400,565
Proceeds from the maturity of and principal paydowns on securities held to maturity			4,634	3,235
Proceeds from the maturity of time deposits in other financial institutions			0	593
Proceeds from the sale, maturity of and principal paydowns on other investments			2,843	6,297
Purchase of securities available for sale			(2,941,662)	(2,777,981)
Purchase of other investments			(10,922)	(10,916)
Net (increase) decrease in loans			150,876
Net (increase) decrease in loans				(746,723)
Purchase of bank owned life insurance policies			(196)	(208)
Proceeds from bank owned life insurance policies			0	606
Capital expenditures			(15,705)	(13,178)
Proceeds from the sale of equipment			7,332	3,339
Net cash expended in divestitures			(15,682)	0
Proceeds on sale of OREO and other repossessed assets			5,032	2,559
NET CASH USED BY INVESTING ACTIVITIES			(1,291,359)	(2,312,742)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in demand deposits			855,996	1,478,704
Net increase in savings deposits			411,864	434,726
Net decrease in time deposit accounts			(198,024)	(190,651)
Net increase in short-term borrowings			97,748	205,277
Proceeds from short term advances			51,700	541,545
Repayments of short term advances			(51,700)	(622,742)
Proceeds from other borrowings			147,614	254,833
Repayments of other borrowings			(233,765)	(7,399)
Net proceeds from the issuance of preferred stock			0	110,705
Proceeds from issuance of common stock			1,716	2,150
Dividends paid			(35,139)	(24,529)
NET CASH PROVIDED BY FINANCING ACTIVITIES			1,048,010	2,182,619
Net decrease in cash and cash equivalents			(10,498)	(47,079)
Cash and cash equivalents at beginning of year			337,903	378,734	$ 378,734
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 327,405	$ 331,655	327,405	331,655	$ 337,903
Supplemental disclosures:
Cash paid for income/franchise taxes			42,425	26,701
Cash paid for interest			21,632	38,088
Loans transferred to OREO			2,713	1,706
Transfer of premises from premises, furniture and equipment, net, to premises, furniture and equipment held for sale			1,564	0
Transfer of premises from premises, furniture and equipment held for sale to premises, furniture and equipment, net			396	450
Dividends declared, not paid			2,013	0
Purchases of securities available for sale, accrued, not settled			0	4,792
Transfer of available for sale securities to held to maturity securities			0	462
Purchases of loans held to maturity accrued, not settled			$ 0	$ 9,600