LOANS AND LEASES - Restructured Loans (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) loans d	Mar. 31, 2017 USD ($) loans	Dec. 31, 2017 USD ($) loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extended Maturities	$ 888,000	$ 674,000
Adjusted Interest Rates	52,000	2,767,000
Combined Rate And Maturity	0	0
Forebearance Agreements	0	0
Other	138,000	0
Total	$ 1,078,000	$ 3,441,000
Restructured loans, Number of Loans | loans	8	2
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 1,093,000	$ 3,502,000
Restructured loans, Period End Balance	$ 1,078,000	3,441,000
Restructured loans with payment default within 12 months of modification, Number of Loans | loans	0		0
Restructured loans with payment default within 12 months of modification, Period End Balance	$ 0	$ 0
Number of Restructured Loans | loans	204		214
Total restructured loans	$ 21,000,000.0		$ 23,900,000
Restructured loans on accrual status	14,943,000		17,545,000
Restructured Loans, Nonaccrual Status	6,000,000.0		6,400,000
Allowance for loan and lease losses lncluded in reserves for restructured loans	2,000,000.0		1,300,000
Restructured loans uncollectible portion written off	100,000
Accruing TDRs performing in accordance with restructured terms for more than one year	$ 13,300,000		$ 17,200,000
Restructured loans performance threshold (days) | d	90
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	4	2
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 928,000	$ 3,502,000
Restructured loans, Period End Balance	$ 913,000	$ 3,441,000
Construction real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	2	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 72,000	$ 0
Restructured loans, Period End Balance	$ 72,000	$ 0
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	2	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 93,000	$ 0
Restructured loans, Period End Balance	93,000	$ 0
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum	$ 250,000
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0
Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0