CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net income	$ 84,714,000	$ 52,581,000
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and net amortization	8,634,000	9,128,000
Securities premium amortization (discount accretion), net	17,709,000	17,954,000
Loan (discount accretion) premium amortization, net	(649,000)	(847,000)
Provision for credit losses	(13,543,000)	25,746,000
Stock compensation expense	2,189,000	2,253,000
Deferred tax expense (benefit)	3,612,000	(4,305,000)
Net gain on sale of AFS securities	(3,399,000)	(8,281,000)
Net loss on premises and equipment	315,000	821,000
Gross proceeds from sales of loans held for sale	36,961,000	48,343,000
Gross originations of loans held for sale	(34,397,000)	(56,646,000)
Net (gain) loss on OREO	(180,000)	129,000
Loss due to curtailment	0	163,000
Loss on redemption of subordinated notes	1,118,000	0
Net change in:
Interest receivable	9,611,000	(1,987,000)
Other assets	(2,803,000)	(35,530,000)
Interest payable	(1,223,000)	(3,673,000)
Other liabilities	19,981,000	4,402,000
Net cash provided by operating activities	128,650,000	50,251,000
Securities AFS:
Purchases	(569,807,000)	(821,232,000)
Sales	104,728,000	291,581,000
Maturities, calls and principal repayments	243,507,000	316,072,000
Securities HTM:
Maturities, calls and principal repayments	16,602,000	19,820,000
Proceeds from redemption of FHLB stock and equity investments	19,240,000	20,000,000
Purchases of FHLB stock and equity investments	(21,113,000)	(5,483,000)
Net loan originations	9,314,000	(222,342,000)
Purchases of premises and equipment	(6,491,000)	(10,216,000)
Purchases of BOLI	(13,000,000)	(12,500,000)
Proceeds from sales of premises and equipment	1,853,000	114,000
Net proceeds from sales of OREO	797,000	277,000
Proceeds from sales of repossessed assets	247,000	158,000
Net cash used in investing activities	(214,123,000)	(423,751,000)
FINANCING ACTIVITIES:
Net change in deposits	399,303,000	420,068,000
Net change in other borrowings	(2,448,000)	13,210,000
Proceeds from FHLB borrowings	11,648,180,000	10,135,401,000
Repayment of FHLB borrowings	(11,821,503,000)	(10,155,201,000)
Net proceeds from issuance of subordinated notes	(95,000)	0
Redemption of subordinated notes	(100,011,000)	0
Proceeds from stock option exercises	6,108,000	1,502,000
Cash paid to tax authority related to tax withholding on share-based awards	(217,000)	(179,000)
Purchase of common stock	(34,148,000)	(25,842,000)
Proceeds from the issuance of common stock for dividend reinvestment plan	986,000	1,020,000
Cash dividends paid	(31,957,000)	(30,972,000)
Net cash provided by financing activities	64,198,000	359,007,000
Net (decrease) increase in cash and cash equivalents	(21,275,000)	(14,493,000)
Cash and cash equivalents at beginning of period	108,408,000	110,697,000
Cash and cash equivalents at end of period	87,133,000	96,204,000
SUPPLEMENTAL DISCLOSURES FOR CASH FLOW INFORMATION:
Interest paid	22,295,000	40,039,000
Income taxes paid	8,750,000	9,000,000
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Loans transferred to other repossessed assets and real estate through foreclosure	740,000	627,000
Unsettled trades to purchase securities	$ (4,433,000)	$ (7,294,000)