Loans Receivable and Related Allowance for Loan Losses - Summary of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 540,892	$ 520,980
Less allowance for loan losses	5,688	5,545	$ 5,352	$ 5,205
Total loans, net	535,204	515,435
Residential first mortgages
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	209,694	198,167
Less allowance for loan losses	1,956	1,846	1,577	1,429
Home equity loans and lines of credit
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	90,648	91,359
Less allowance for loan losses	648	633	636	586
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	178,024	166,994
Less allowance for loan losses	2,449	2,314	1,926	2,185
Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	55,753	57,788
Less allowance for loan losses	583	700	1,162	960
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	6,773	6,672
Less allowance for loan losses	52	52	$ 51	$ 45
Mortgage loans on real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	478,366	456,520
Mortgage loans on real estate | Residential first mortgages
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	209,694	198,167
Mortgage loans on real estate | Home equity loans and lines of credit
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	90,648	91,359
Mortgage loans on real estate | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	178,024	166,994
Other loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	62,526	64,460
Other loans | Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	55,753	57,788
Other loans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 6,773	$ 6,672