LOANS AND LEASES - Restructured Loans (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) loans d	Mar. 31, 2020 USD ($) loans	Dec. 31, 2020 USD ($) loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	22	21
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 14,258	$ 12,724
Financing Receivable, Troubled Debt Restructuring, Postmodification	13,130	12,657
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 0	0
Number of Restructured Loans | loans	173		155
Total restructured loans	$ 32,500		$ 21,800
Restructured loans on accrual status	11,600		7,100
Restructured Loans, Nonaccrual Status	20,900		14,700
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	300		300
Allowance for loan and lease losses lncluded in reserves for restructured loans	8,000		8,800
Accruing TDRs performing in accordance with restructured terms for more than one year	5,200		$ 5,000
Restructured Loans, Portion Determined to be Uncollectible	$ 30	$ 400
Restructured loans performance threshold (days) | d	90
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | loans	0	0
Commercial segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	4	2
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 3,206	$ 11,383
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 3,070	$ 11,383
Construction real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	0	0
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 0
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 0	$ 0
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	7	0
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 10,015	$ 0
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 9,046	$ 0
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	10	14
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 1,023	$ 1,129
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 1,000	$ 1,073
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	1	4
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 14	$ 186
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 14	$ 186
Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	0	1
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 0	$ 26
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 0	$ 15
Payment Deferral [Member] | Commercial segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	67		90
Total restructured loans	$ 248,400		$ 312,500
Payment Deferral [Member] | Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Number of Contracts | loans	25		53
Total restructured loans	$ 2,700		$ 7,700