LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES - Allowance for credit losses (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2019 USD ($) borrower	Sep. 30, 2018 USD ($) borrower	Dec. 31, 2018 USD ($)
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Average loans	$ 293,958,000	$ 283,006,000
Net charge-offs to average loans (annualized)	0.14%	0.35%
Number of borrowers \| borrower	47	43
Loans charged off	$ 519,000	$ 954,000	$ 1,151,000
Outstanding commitments	35,500,000	31,400,000
Unfunded commitments
Beginning balance	35,000	24,000	24,000
Reduction of unfunded reserve	(23,000)	(45,000)
Provisions charged to operations	25,000	46,000
Ending balance	$ 37,000	$ 25,000	$ 35,000

Amount of writeoff of financing receivable, charged against allowance for credit loss.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 55
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
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