Loans Receivable - Credit Quality Indicators by Class of Loan (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 905,675	$ 883,757
Recorded investment, nonaccrual loans	1,740	1,796
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	876,882	865,674
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	18,480	8,055
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	5,737	5,078
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,576	4,950
Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,740	1,796
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	903,935	881,961
Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	700,368	695,021
Real Estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	679,934	684,434
Real Estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	13,902	3,966
Real Estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,281	4,132
Real Estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,251	2,489
Real Estate | Real estate loans | One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	302,688	306,014
Recorded investment, nonaccrual loans	467	698
Real Estate | Real estate loans | One-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	297,391	301,312
Real Estate | Real estate loans | One-to-four family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,455	2,685
Real Estate | Real estate loans | One-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,206	1,148
Real Estate | Real estate loans | One-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	636	869
Real Estate | Real estate loans | One-to-four family | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	467	698
Real Estate | Real estate loans | One-to-four family | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	302,221	305,316
Real Estate | Real estate loans | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	88,794	96,098
Recorded investment, nonaccrual loans		0
Real Estate | Real estate loans | Multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	88,390	95,694
Real Estate | Real estate loans | Multi-family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Real Estate | Real estate loans | Multi-family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	107	107
Real Estate | Real estate loans | Multi-family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	297	297
Real Estate | Real estate loans | Multi-family | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	297	0
Real Estate | Real estate loans | Multi-family | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	88,497	96,098
Real Estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	260,321	255,722
Recorded investment, nonaccrual loans	106	109
Real Estate | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	256,166	251,531
Real Estate | Commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	94	97
Real Estate | Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,782	2,800
Real Estate | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,279	1,294
Real Estate | Commercial real estate | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	106	109
Real Estate | Commercial real estate | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	260,215	255,613
Real Estate | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	48,565	37,187
Recorded investment, nonaccrual loans	28	29
Real Estate | Construction and land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	37,987	35,897
Real Estate | Construction and land | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,353	1,184
Real Estate | Construction and land | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	186	77
Real Estate | Construction and land | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	39	29
Real Estate | Construction and land | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	28	29
Real Estate | Construction and land | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	48,537	37,158
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	149,454	147,165
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	143,054	141,587
Consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,518	3,713
Consumer | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	886	683
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	996	1,182
Consumer | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,260	35,046
Recorded investment, nonaccrual loans	133	112
Consumer | Home equity | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	34,196	34,260
Consumer | Home equity | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	712	470
Consumer | Home equity | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	127	89
Consumer | Home equity | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	225	227
Consumer | Home equity | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	133	112
Consumer | Home equity | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,127	34,934
Consumer | Auto and other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	114,194	112,119
Recorded investment, nonaccrual loans	709	848
Consumer | Auto and other consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	108,858	107,327
Consumer | Auto and other consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,806	3,243
Consumer | Auto and other consumer | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	759	594
Consumer | Auto and other consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	771	955
Consumer | Auto and other consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	709	848
Consumer | Auto and other consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	113,485	111,271
Commercial business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	55,853	41,571
Commercial business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	53,894	39,653
Commercial business | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	60	376
Commercial business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	570	263
Commercial business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,329	1,279
Commercial business | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial business | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 55,853	$ 41,571