Loans Receivable and Allowance for Loan Losses - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) contract	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) contract	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable | $	$ 530,389	$ 530,389	$ 530,389	$ 519,132	$ 519,132	$ 519,132
Troubled debt restructuring loans | $	$ 11,300	11,300	$ 11,300	$ 11,400	11,400	$ 11,400
Number of contracts	2		7	1		1
Number of troubled debt restructuring into which loans were modified | loan			2
Interest income on impaired loans | $		443			543
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Troubled debt restructuring loans | $	$ 9,500	9,500	$ 9,500	$ 10,500	10,500	$ 10,500
Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Troubled debt restructuring loans | $	$ 1,800	$ 1,800	$ 1,800	$ 915	$ 915	$ 915
One-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Number of troubled debt restructuring into which loans were modified | loan			1
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Number of contracts | loan			2
Commercial overdraft
Financing Receivable, Credit Quality Indicator [Line Items]
Number of contracts | loan			2
Commercial owner
Financing Receivable, Credit Quality Indicator [Line Items]
Number of troubled debt restructuring into which loans were modified | loan			1