Loans Receivable and Allowance for Loan Losses - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	$ 2,429	$ 3,373
Accruing Current Balances	508,207	500,450
Nonaccrual Loans	3,108	4,131
Ending balance	513,744	507,954
30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	2,142	2,931
60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	287	440
Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	2
Residential Mortgage
Financing Receivable, Past Due [Line Items]
Ending balance	153,769	167,706
Residential Mortgage | One-to-four family
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	2,006	1,695
Accruing Current Balances	127,747	139,371
Nonaccrual Loans	1,169	2,276
Ending balance	130,922	143,342
Residential Mortgage | One-to-four family | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	1,719	1,328
Residential Mortgage | One-to-four family | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	287	365
Residential Mortgage | One-to-four family | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	2
Residential Mortgage | Home equity
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	160	1,677
Accruing Current Balances	21,744	22,079
Nonaccrual Loans	943	608
Ending balance	22,847	24,364
Residential Mortgage | Home equity | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	160	1,602
Residential Mortgage | Home equity | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	75
Residential Mortgage | Home equity | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Commercial and multi-family real estate
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	260	0
Accruing Current Balances	225,841	211,258
Nonaccrual Loans	996	1,032
Ending balance	227,097	212,290
Commercial and multi-family real estate | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	260	0
Commercial and multi-family real estate | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Commercial and multi-family real estate | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Construction
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Accruing Current Balances	31,465	18,905
Nonaccrual Loans	0	0
Ending balance	31,465	18,905
Construction | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Construction | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Construction | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Accruing Current Balances	100,981	108,298
Nonaccrual Loans	0	215
Ending balance	100,981	108,513
Commercial and Industrial | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Commercial and Industrial | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Commercial and Industrial | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	3	1
Accruing Current Balances	429	539
Nonaccrual Loans	0	0
Ending balance	432	540
Consumer | 30-59 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	3	1
Consumer | 60-89 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	0	0
Consumer | Greater than 90 Days and Still Accruing
Financing Receivable, Past Due [Line Items]
Total Past Due and Still Accruing	$ 0	$ 0