LOANS AND LEASES - Collateral (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 9,933,969	$ 9,900,970
Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	28,057	36,803
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	33,768	29,837
Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	417	3,269
Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,238	6,444
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	16,185	17,893
Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	581	5,055
Total Collateral
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	85,246	99,301
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	24,941	45,456
Commercial | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	22,215	30,961
Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,874	6,130
Commercial | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	417	2,608
Commercial | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	865
Commercial | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Commercial | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	435	4,892
Commercial real estate - investor
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	31,527	27,282
Commercial real estate - investor | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Commercial real estate - investor | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	25,115	20,212
Commercial real estate - investor | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	661
Commercial real estate - investor | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,198	5,537
Commercial real estate - investor | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	214	872
Commercial real estate - investor | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Commercial Real Estate-Owner
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	12,987	9,723
Commercial Real Estate-Owner | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,842	5,842
Commercial Real Estate-Owner | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,779	3,495
Commercial Real Estate-Owner | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Commercial Real Estate-Owner | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	40	42
Commercial Real Estate-Owner | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	326	344
Commercial Real Estate-Owner | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	11,359	11,601
Residential real estate | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Residential real estate | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Residential real estate | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Residential real estate | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Residential real estate | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	11,359	11,601
Residential real estate | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Home Equity Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,286	5,076
Home Equity Loan | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Home Equity Loan | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Home Equity Loan | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Home Equity Loan | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Home Equity Loan | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,286	5,076
Home Equity Loan | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	146	163
Installment | Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment | Equipment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment | Land
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Installment | Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 146	$ 163