LOANS AND SERVICING - Summary of loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Summary of loans:
Loans receivable	$ 281,669	$ 279,492
Total loans (as a percent)	100.00%	100.00%
Other items:
Net deferred loan costs	$ 540	$ 484
Allowance for loan losses	(2,642)	(2,605)	$ (2,483)	$ (2,408)
Total loans, net	279,567	277,371
Residential loans:
Summary of loans:
Loans receivable	$ 108,337	$ 106,069
Total loans (as a percent)	38.46%	37.95%
One- to four- family, residential loans
Summary of loans:
Loans receivable	$ 92,869	$ 90,190
Total loans (as a percent)	32.97%	32.27%
Other items:
Allowance for loan losses	$ (176)	$ (171)	(180)	(197)
Home equity loans and lines of credit
Summary of loans:
Loans receivable	$ 15,468	$ 15,879
Total loans (as a percent)	5.49%	5.68%
Other items:
Allowance for loan losses	$ (232)	$ (238)	(260)	(276)
Commercial loans:
Summary of loans:
Loans receivable	$ 151,855	$ 148,087
Total loans (as a percent)	53.91%	52.98%
One-to-four family investment property
Summary of loans:
Loans receivable	$ 14,400	$ 13,081
Total loans (as a percent)	5.11%	4.68%
Other items:
Allowance for loan losses	$ (86)	$ (79)	(83)	(90)
Multi-family real estate
Summary of loans:
Loans receivable	$ 30,214	$ 30,748
Total loans (as a percent)	10.73%	11.00%
Other items:
Allowance for loan losses	$ (230)	$ (234)	(226)	(233)
Commercial real estate
Summary of loans:
Loans receivable	$ 83,390	$ 83,583
Total loans (as a percent)	29.60%	29.90%
Other items:
Allowance for loan losses	$ (1,259)	$ (1,262)	(1,126)	(1,021)
Commercial business loan
Summary of loans:
Loans receivable	$ 23,851	$ 20,675
Total loans (as a percent)	8.47%	7.40%
Other items:
Allowance for loan losses	$ (419)	$ (364)	(338)	(305)
Construction loans
Summary of loans:
Loans receivable	$ 21,327	$ 25,154
Total loans (as a percent)	7.58%	9.00%
One-to-four family, construction loans
Summary of loans:
Loans receivable	$ 9,368	$ 12,599
Total loans (as a percent)	3.33%	4.51%
Other items:
Allowance for loan losses	$ (82)	$ (104)	(139)	(113)
Multi-family
Summary of loans:
Loans receivable	$ 4,505	$ 5,725
Total loans (as a percent)	1.60%	2.05%
Other items:
Allowance for loan losses	$ (37)	$ (47)	(14)	(12)
Non-residential
Summary of loans:
Loans receivable	$ 7,454	$ 6,830
Total loans (as a percent)	2.65%	2.44%
Other items:
Allowance for loan losses	$ (114)	$ (104)	(97)	(91)
Consumer
Summary of loans:
Loans receivable	$ 150	$ 182
Total loans (as a percent)	0.05%	0.07%
Other items:
Allowance for loan losses	$ (1)	$ (2)	$ (2)	$ (2)