LOANS AND THE ALLOWANCE FOR LOAN LOSSES - Summary of unpaid principal balance of loans classified as TDRs (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) loan	Mar. 31, 2018 USD ($) loan	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Recorded Investment	$ 17,500	$ 1,835	$ 17,835
Allowance for loan associated with TDR	(940)	$ (722)	(940)
Net recorded investment	16,560		$ 16,895
Additional funds to loans classified as TDRs	300
Cash collateral received	$ 1,500
Number of contracts modified	0	0	2
Cash, Securities and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Recorded Investment	$ 10,977		$ 11,252
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Recorded Investment	6,523	$ 1,835	6,583
Allowance for loan associated with TDR	(940)	$ (722)	(940)
Investment accruing interest	5,100		5,100
Investment non-accruing interest	$ 1,400		$ 1,400