Loans - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	$ 617,589	$ 615,498
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	541,440	531,848
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	53,795	59,061
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	14,070	15,062
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	8,284	9,527
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Real estate loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	458,329	475,448
Consumer loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	75,591	75,833
Commercial business
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	83,669	64,217
Commercial business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	77,199	56,743
Commercial business | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	4,392	5,202
Commercial business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	465	310
Commercial business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	1,613	1,962
Commercial business | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Commercial business | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
One-to-four family | Real estate loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	129,995	130,657
One-to-four family | Real estate loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	123,661	113,185
One-to-four family | Real estate loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	4,221	15,142
One-to-four family | Real estate loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
One-to-four family | Real estate loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	2,113	2,330
One-to-four family | Real estate loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
One-to-four family | Real estate loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Home equity | Real estate loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	13,763	16,265
Home equity | Real estate loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	13,152	15,556
Home equity | Real estate loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	178	245
Home equity | Real estate loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Home equity | Real estate loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	433	464
Home equity | Real estate loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Home equity | Real estate loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Commercial and multifamily | Real estate loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	251,459	265,774
Commercial and multifamily | Real estate loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	208,405	228,652
Commercial and multifamily | Real estate loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	30,369	22,945
Commercial and multifamily | Real estate loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	10,062	10,813
Commercial and multifamily | Real estate loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	2,623	3,364
Commercial and multifamily | Real estate loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Commercial and multifamily | Real estate loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Construction and land | Real estate loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	63,112	62,752
Construction and land | Real estate loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	45,293	44,360
Construction and land | Real estate loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	13,511	13,808
Construction and land | Real estate loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	3,543	3,939
Construction and land | Real estate loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	765	645
Construction and land | Real estate loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Construction and land | Real estate loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Manufactured homes | Consumer loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	20,781	20,941
Manufactured homes | Consumer loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	20,063	19,606
Manufactured homes | Consumer loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	518	1,115
Manufactured homes | Consumer loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Manufactured homes | Consumer loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	200	220
Manufactured homes | Consumer loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Manufactured homes | Consumer loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Floating homes | Consumer loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	39,868	39,868
Floating homes | Consumer loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	38,750	38,746
Floating homes | Consumer loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	604	604
Floating homes | Consumer loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Floating homes | Consumer loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	514	518
Floating homes | Consumer loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Floating homes | Consumer loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Other consumer | Consumer loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	14,942	15,024
Other consumer | Consumer loans: | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	14,917	15,000
Other consumer | Consumer loans: | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	2	0
Other consumer | Consumer loans: | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Other consumer | Consumer loans: | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	23	24
Other consumer | Consumer loans: | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	0	0
Other consumer | Consumer loans: | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held-for-portfolio	$ 0	$ 0