Derivative Financial Instruments (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Interest rate swap fair value (asset)	$ 800	$ 700
Gain on derivative	81
Deferred tax asset on gain on derivative	$ 22
Cash flow hedge ineffectiveness	Interest rate swap agreements are entered into with counterparties that meet established credit standards and the Corporation believes that the credit risk inherent in these contracts is not significant as of December 31, 2017.
Cash Flow Hedge [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 30,000
Number of interest rate swap contracts | contract	4
Derivative Matured [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 20,000
Number of interest rate swap contracts | contract	3
Derivative, maturity date	Jun. 17, 2016
Swap Contract 3 Year 5 Million [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 5,000
Derivative, maturity date	Jun. 17, 2019
Swap Contract 5 Year $5 Million [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 5,000
Derivative, maturity date	Mar. 17, 2021
Swap Contract- 7 year $5 Million [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 5,000
Derivative, maturity date	Mar. 17, 2023
Swap Contract 10 Year $15 Million [Member]
Derivative [Line Items]
Interest rate swap notional amount	$ 15,000
Derivative, maturity date	Mar. 17, 2026