LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES - Impaired Financing Receivables (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Recorded Investment with specific reserves	$ 27,000	$ 27,000
Unpaid Principal Balance with specific reserves	37,000	38,000
Interest Income Recognized with specific reserves	1,000	2,000
Specific Reserve with specific reserves	10,000	11,000
Average Recorded Investment	49,000	50,000
Recorded Investment with no specific reserve	2,744,000	4,876,000
Unpaid Principal Balance with no specific reserve	2,744,000	4,876,000
Interest Income Recognized with no specific reserve	340,000	199,000
Average Recorded Investment with no specific reserve	3,220,000	5,129,000
Real Estate Loan
Financing Receivable, Impaired [Line Items]
Recorded Investment with specific reserves	27,000	27,000
Unpaid Principal Balance with specific reserves	37,000	38,000
Interest Income Recognized with specific reserves	1,000	2,000
Specific Reserve with specific reserves	10,000	11,000
Average Recorded Investment	49,000	50,000
Recorded Investment with no specific reserve	2,547,000	4,725,000
Unpaid Principal Balance with no specific reserve	2,547,000	4,725,000
Interest Income Recognized with no specific reserve	334,000	185,000
Average Recorded Investment with no specific reserve	3,000,000	4,859,000
Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	71,000
Unpaid Principal Balance with no specific reserve	71,000
Interest Income Recognized with no specific reserve	1,000
Average Recorded Investment with no specific reserve	71,000
Consumer Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	126,000	151,000
Unpaid Principal Balance with no specific reserve	126,000	151,000
Interest Income Recognized with no specific reserve	5,000	14,000
Average Recorded Investment with no specific reserve	149,000	270,000
Single-family \| Real Estate Loan
Financing Receivable, Impaired [Line Items]
Recorded Investment with specific reserves	27,000	27,000
Unpaid Principal Balance with specific reserves	37,000	38,000
Interest Income Recognized with specific reserves	1,000	2,000
Specific Reserve with specific reserves	10,000	11,000
Average Recorded Investment	49,000	50,000
Recorded Investment with no specific reserve	95,000	232,000
Unpaid Principal Balance with no specific reserve	95,000	232,000
Interest Income Recognized with no specific reserve	1,000
Average Recorded Investment with no specific reserve	99,000	544,000
Single-family \| Consumer Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with specific reserves	36,532
Specific Reserve	10,359
Commercial \| Real Estate Loan
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	2,452,000	4,493,000
Unpaid Principal Balance with no specific reserve	2,452,000	4,493,000
Interest Income Recognized with no specific reserve	333,000	185,000
Average Recorded Investment with no specific reserve	2,901,000	4,315,000
SBA Guaranty \| Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	71,000
Unpaid Principal Balance with no specific reserve	71,000
Interest Income Recognized with no specific reserve	1,000
Average Recorded Investment with no specific reserve	71,000
Consumer and Indirect \| Consumer Loans
Financing Receivable, Impaired [Line Items]
Specific Reserve with specific reserves		11,000
Recorded Investment with no specific reserve		34,000
Unpaid Principal Balance with no specific reserve		34,000
Interest Income Recognized with no specific reserve		4,000
Average Recorded Investment with no specific reserve		43,000
Automobile \| Consumer Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	126,000	117,000
Unpaid Principal Balance with no specific reserve	126,000	117,000
Interest Income Recognized with no specific reserve	5,000	10,000
Average Recorded Investment with no specific reserve	$ 149,000	$ 227,000

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

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Amount of allowance for credit losses related to recorded investment.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of interest income, recognized on cash basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 10
-Section 50
-Paragraph 15
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-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

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-Section 50
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-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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