LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES - Non-accrual loans (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	$ 4,512	$ 4,127
Transfer into non-accrual	1,055	831
Loans paid down/payoffs	(685)	(252)
Loans return to accrual status	(650)	(594)
Loans charged off	(123)	(171)
Balance	4,109	3,941
Real Estate Loan
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	4,299
Balance	3,971
Consumer Loans
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	213
Single-family residential | Real Estate Loan
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	270	790
Loans paid down/payoffs	(136)	(139)
Balance	134	651
Multifamily | Real Estate Loan
Financing Receivable Nonaccrual Status [Roll Forward]
Balance		24
Loans paid down/payoffs		(5)
Balance		19
Commercial | Real Estate Loan
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	4,029	3,139
Transfer into non-accrual	920	577
Loans paid down/payoffs	(496)	(67)
Loans return to accrual status	(616)	(577)
Balance	3,837	3,072
Commercial | Consumer Loans
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	138
Consumer | Consumer Loans
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	34	51
Transfer into non-accrual	1
Loans paid down/payoffs	(1)	(6)
Loans return to accrual status	(34)
Balance		45
Automobile | Consumer Loans
Financing Receivable Nonaccrual Status [Roll Forward]
Balance	179	123
Transfer into non-accrual	134	254
Loans paid down/payoffs	(52)	(35)
Loans return to accrual status		(17)
Loans charged off	(123)	(171)
Balance	$ 138	$ 154