Short-Term Borrowings and Long-Term Debt (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Repayments Of Long Term Debt	$ 20,061	$ 5,058	$ 19,055
Proceeds From Issuance Of Long-Term Debt	10,000	15,000
Long-Term Debt	55,498	65,559	$ 55,617
Due in 2018	35,000	20,000
Due in 2022	10,302
Daily advances outstanding	6,000	19,000
Short-term advances	81,500	60,000
Fixed Rate Advance Matures in 2018 [Member]
Debt Instrument [Line Items]
Proceeds From Issuance Of Long-Term Debt	$ 10,000	$ 15,000
Interest rate	1.38%	0.95%
Federal Reserve Bank Of Richmond [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 7,500	$ 8,600
Other Commercial Banks [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	22,000	12,000
Credit Facility With Commercial Bank [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	40,000
Federal Home Loan Bank Borrowings [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	309,600	261,100
Security owned and pledged as collateral, fair value	584,600	521,300
FHLB lendable collateral	452,600	405,700
FHLB lendable pledged collateral	330,100	275,100
Line of credit facility, current borrowing capacity	187,100	130,600
Line of credit facility, fair value of amount outstanding	143,000	144,600
FHLB lendable unpledged collateral	122,500	130,500
Advances and Security Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 420,300	$ 399,600
Percentage of assets limited to maximum borrowing capacity	30.00%