Short-Term Borrowings and Long-Term Debt (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Debt paid off	$ 5,000,000	$ 19,000,000
Percentage of the long term debt exercised or expired	100.00%	100.00%
Long term debt exercised or expired	$ 65,600,000	$ 55,600,000
Line of credit facility, fair value of amount outstanding	7,000,000
Short-term loan	60,000,000	29,000,000
Due in 2017	$ 20,000,000	5,000,000
Due in 2021		10,000,000
Fixed Rate Advance Matures in 2018 [Member]
Debt Instrument [Line Items]
Interest rate	0.95%
Proceeds from Issuance of Debt	$ 15,000,000
Federal Reserve Bank Of Richmond [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	8,600,000	7,200,000
Line of credit facility, fair value of amount outstanding	0	0
Other Commercial Banks [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		12,000,000	$ 12,000,000
Line of credit facility, fair value of amount outstanding	$ 0	0
Fixed Rate Convertible Advances [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2020
Debt conversion, converted instrument, rate	4.00%
Federal Home Loan Bank Borrowings [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 261,100,000	185,600,000
Security owned and pledged as collateral, fair value	521,300,000	365,400,000
FHLB lendable collateral	405,700,000	277,200,000
FHLB lendable pledged collateral	275,100,000	165,800,000
Line of credit facility, current borrowing capacity	130,600,000	74,200,000
Line of credit facility, fair value of amount outstanding	144,600,000	91,600,000
FHLB lendable unpledged collateral	$ 130,500,000	111,400,000
Maximum [Member] | Fixed Rate Convertible Advances [Member]
Debt Instrument [Line Items]
Variable convertible debt maturity period	5 years
Minimum [Member] | Fixed Rate Convertible Advances [Member]
Debt Instrument [Line Items]
Variable convertible debt maturity period	6 months
Advances and Security Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 399,600,000	$ 332,800,000
Percentage of assets limited to maximum borrowing capacity	30.00%