Loans (Composition of Total Loans Outstanding) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 816,525		$ 817,529
Less allowance for credit losses	(5,267)	$ (5,418)	(5,373)	$ (5,247)	$ (5,172)	$ (4,935)
Net loans	811,258		812,156
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	86,632		87,581
Less allowance for credit losses	(245)	(247)	(349)	(314)	(220)	(216)
Commercial Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	453,453		465,486
Less allowance for credit losses	(2,634)	(2,597)	(2,531)	(2,370)	(2,376)	(2,375)
Commercial Term [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	118,490		123,175
Less allowance for credit losses	(625)	(774)	(709)	(891)	(948)	(989)
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	92,157		72,755
Less allowance for credit losses	(1,208)	(1,059)	(969)	(866)	(765)	(569)
Consumer: Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	59,829		62,560
Less allowance for credit losses	(189)	(196)	(196)	(191)	(188)	(195)
Consumer: Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,964		5,972
Less allowance for credit losses	$ (84)	$ (63)	$ (61)	$ (64)	$ (67)	$ (64)