Loan Quality (Troubled Debt Restructuring Loans) (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Number of Contracts | contract		17	17
Troubled Debt Restructurings: Recorded Investment		$ 12,186	$ 13,419
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Number of Contracts | contract		2	2
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Recorded Investment		$ 634	$ 1,401
New During Period, Number of Contracts | contract		0	2
New During Period, Pre-TDR Modification			$ 763
New During Period, After-TDR Modification			763
New During Period, Recorded Investment			750
Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	$ 11,555	12,018
Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	$ 631	$ 1,401
Residential Real Estate - Construction [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Number of Contracts | contract		1	1
Troubled Debt Restructurings: Recorded Investment		$ 466	$ 480
Residential Real Estate - Construction [Member] | Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	$ 466	$ 480
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Number of Contracts | contract		5	5
Troubled Debt Restructurings: Recorded Investment		$ 737	$ 875
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Number of Contracts | contract		1	1
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Recorded Investment		$ 39	$ 151
New During Period, Number of Contracts | contract			1
New During Period, Pre-TDR Modification			$ 238
New During Period, After-TDR Modification			238
New During Period, Recorded Investment			237
Residential Real Estate [Member] | Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	701	724
Residential Real Estate [Member] | Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	$ 36	$ 151
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Number of Contracts | contract		11	11
Troubled Debt Restructurings: Recorded Investment		$ 10,983	$ 12,064
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Number of Contracts | contract		1	1
Troubled Debt Restructurings That Have Defaulted on Modified Terms in the Last Twelve Months: Recorded Investment		$ 595	$ 1,250
New During Period, Number of Contracts | contract			1
New During Period, Pre-TDR Modification			$ 525
New During Period, After-TDR Modification			525
New During Period, Recorded Investment			513
Commercial Real Estate [Member] | Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	10,388	10,814
Commercial Real Estate [Member] | Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructurings: Recorded Investment	[1]	$ 595	$ 1,250

[1] The performing status is determined by the loan's compliance with the modified terms.