SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Allowance for Loan Losses Allocated
Historical loss experience period used to determine specific and general components of allowance	3 years
Minimum
Loans
Past due period of payments of loans	90 days
Allowance for Loan Losses Allocated
Basis points floor of historical losses used to reflect minimum level of risk	0.15%
Amount of impaired loans for which specific reserve is established	$ 250
Minimum | Residential
Allowance for Loan Losses Allocated
Financing term of loans	15 years
Minimum | Consumer
Allowance for Loan Losses Allocated
Financing term of loans	3 years
Maximum | Residential
Allowance for Loan Losses Allocated
Financing term of loans	30 years
Maximum | Consumer
Allowance for Loan Losses Allocated
Financing term of loans	7 years