Fair Values of Financial Instruments - Assets Measured at Fair Value on a Non-recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	$ 1,103	$ 609
Level 1
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0	0
Level 2
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0	0
Level 3
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	1,103	609
Impaired residential mortgage loan
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	58
Impaired residential mortgage loan | Level 1
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0
Impaired residential mortgage loan | Level 2
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0
Impaired residential mortgage loan | Level 3
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	58
Impaired commercial real estate loan
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	463
Impaired commercial real estate loan | Level 1
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0
Impaired commercial real estate loan | Level 2
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0
Impaired commercial real estate loan | Level 3
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	463
Impaired commercial business loan
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	582	596
Impaired commercial business loan | Level 1
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0	0
Impaired commercial business loan | Level 2
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	0	0
Impaired commercial business loan | Level 3
Financing Receivable, Impaired [Line Items]
Unpaid principal balance	$ 582	596
Other residential real estate owned
Financing Receivable, Impaired [Line Items]
Unpaid principal balance		13
Other residential real estate owned | Level 1
Financing Receivable, Impaired [Line Items]
Unpaid principal balance		0
Other residential real estate owned | Level 2
Financing Receivable, Impaired [Line Items]
Unpaid principal balance		0
Other residential real estate owned | Level 3
Financing Receivable, Impaired [Line Items]
Unpaid principal balance		$ 13