LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES - Summary of Allowance for credit losses (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Financing Receivable, Impaired [Line Items]
Troubled debt restructured loans | $	$ 260,000	$ 263,000
Non-accrual and 90 days or more and still accruing loans to gross loans	2.09%	1.32%
Allowance for credit losses to non-accrual and 90 days or more and still accruing loans	52.70%	77.70%
Number of TDRs contracts | loan	2	2
Commercial
Financing Receivable, Impaired [Line Items]
Troubled debt restructured loans | $	$ 214,000
Number of TDRs contracts | loan	1	1
Consumer
Financing Receivable, Impaired [Line Items]
Troubled debt restructured loans | $	$ 46,000
Number of TDRs contracts | loan	1	1