CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
OPERATING ACTIVITIES:
Net income	$ 55,408,000	$ 25,507,000
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and net amortization	5,780,000	6,053,000
Securities premium amortization (discount accretion), net	12,186,000	11,178,000
Loan (discount accretion) premium amortization, net	(683,000)	(406,000)
Provision for credit losses	(8,472,000)	30,492,000
Stock compensation expense	1,360,000	1,467,000
Deferred tax expense (benefit)	2,022,000	(4,955,000)
Net gain on sale of AFS securities	(2,018,000)	(8,203,000)
Net loss on premises and equipment	302,000	59,000
Gross proceeds from sales of loans held for sale	27,286,000	25,633,000
Gross originations of loans held for sale	(26,101,000)	(28,642,000)
Net (gain) loss on OREO	(2,000)	9,000
Retirement plan curtailment expense	0	163,000
Net change in:
Interest receivable	2,112,000	(8,401,000)
Other assets	8,409,000	(9,804,000)
Interest payable	(784,000)	(1,404,000)
Other liabilities	3,414,000	(21,277,000)
Net cash provided by operating activities	80,219,000	17,469,000
Securities AFS:
Purchases	(392,788,000)	(711,897,000)
Sales	46,720,000	285,478,000
Maturities, calls and principal repayments	181,956,000	187,896,000
Securities HTM:
Maturities, calls and principal repayments	14,220,000	14,405,000
Proceeds from redemption of FHLB stock and equity investments	16,240,000	0
Purchases of FHLB stock and equity investments	(18,973,000)	(5,545,000)
Net loan originations	15,333,000	(284,755,000)
Purchases of premises and equipment	(4,507,000)	(7,886,000)
Purchases of BOLI	0	(12,500,000)
Proceeds from sales of premises and equipment	1,850,000	86,000
Net proceeds from sales of OREO	59,000	186,000
Proceeds from sales of repossessed assets	44,000	54,000
Net cash used in investing activities	(139,846,000)	(534,478,000)
FINANCING ACTIVITIES:
Net change in deposits	223,822,000	387,651,000
Net change in other borrowings	611,000	42,947,000
Proceeds from FHLB borrowings	7,080,064,000	5,047,401,000
Repayment of FHLB borrowings	(7,191,223,000)	(4,925,987,000)
Net proceeds from issuance of subordinated long-term debt	(95,000)	0
Proceeds from stock option exercises	5,979,000	1,130,000
Cash paid to tax authority related to tax withholding on share-based awards	(152,000)	(138,000)
Purchase of common stock	(18,710,000)	(25,842,000)
Proceeds from the issuance of common stock for dividend reinvestment plan	662,000	683,000
Cash dividends paid	(21,251,000)	(20,727,000)
Net cash provided by financing activities	79,707,000	507,118,000
Net increase (decrease) in cash and cash equivalents	20,080,000	(9,891,000)
Cash and cash equivalents at beginning of period	108,408,000	110,697,000
Cash and cash equivalents at end of period	128,488,000	100,806,000
SUPPLEMENTAL DISCLOSURES FOR CASH FLOW INFORMATION:
Interest paid	14,984,000	28,679,000
Income taxes paid	6,250,000	5,000,000
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Loans transferred to other repossessed assets and real estate through foreclosure	531,000	380,000
Unsettled trades to purchase securities	(41,888,000)	(26,359,000)
Unsettled trades to sell securities	$ 0	$ 2,923,000