Loans (Composition of Total Loans Outstanding) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 864,345	$ 845,897
Less allowance for credit losses	(6,145)	(5,843)	$ (5,418)	$ (5,373)
Net loans	858,200	840,054
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	95,404	93,959
Less allowance for credit losses	(226)	(221)	(247)	(349)
Commercial Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	498,506	484,868
Less allowance for credit losses	(2,987)	(2,856)	(2,597)	(2,531)
Commercial Term [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	131,144	129,535
Less allowance for credit losses	(904)	(845)	(774)	(709)
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	78,863	75,014
Less allowance for credit losses	(1,219)	(1,128)	(1,059)	(969)
Consumer: Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	55,002	56,844
Less allowance for credit losses	(176)	(183)	(196)	(196)
Consumer: Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,426	5,677
Less allowance for credit losses	$ (55)	$ (63)	$ (63)	$ (61)