ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) SecurityLoan loan	Mar. 31, 2018 USD ($) loan	Dec. 31, 2018 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ 900,000	$ 3,400,000
Percentage of average loans annualized, charged-offs	0.06%	0.29%
Interest income on impaired loans	$ 200,000	$ 300,000
Troubled debt restructuring related reserves	$ 1,100,000		$ 1,200,000
Usual sustained repayment performance period	6 months
TRD defaulted | loan	1	2
Subsequent default, loan amount, less than	$ 100,000	$ 100,000
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of residential loans in the process of foreclosure | SecurityLoan	17		26
Total loans outstanding, residential loans	$ 1,200,000		$ 1,900,000
Commercial and Industrial (1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of residential loans in the process of foreclosure | SecurityLoan	13		11
Total loans outstanding, residential loans	$ 5,600,000		$ 5,300,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for impairment loans	90 days
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in allowance for loan losses (less than)	$ (100,000)
Troubled debt restructurings charged off	$ 0	$ 0
Total Residential and Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment loans, charge off period	90 days