Subordinated Debentures, Notes, And Other Borrowings (Narrative) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Mar. 05, 2015 USD ($)
Debt Instrument [Line Items]
Number of issuances of junior subordinated debentures | item	2
Repurchase agreements	$ 4,089,000	$ 12,023,000
State and municipal securites sold	$ 4,200,000	$ 12,300,000
Repurchase agreement amount, percentage	102.00%	102.00%
Subordinated Note [Member]
Debt Instrument [Line Items]
Interest rate period, in years	5 years
Debt instrument, face amount			$ 9,750,000
Debt maturity date	Mar. 06, 2025
Subordinated Note [Member] | Maximum [Member]
Debt Instrument [Line Items]
Variable interest rate	5.75%
Subordinated Note [Member] | Minimum [Member]
Debt Instrument [Line Items]
Variable interest rate	3.00%
Fixed Rate, First 5 Years [Member] | Subordinated Note [Member]
Debt Instrument [Line Items]
Subordinate notes bearing fixed interest rate	4.25%
Prime Rate [Member] | Subordinated Note [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
DNB Capital Trust I [Member]
Debt Instrument [Line Items]
Issuance date	Jul. 20, 2001
Floating rate capital preferred securities	$ 5,000,000
LIBOR rate, borrowing period, in months	6 months
Basis spread on variable rate	3.75%
Fixed interest rate	12.00%
Principal amount, floating rate junior subordinated debentures	$ 5,200,000
Maturity date range, start	Jul. 25, 2006
Maturity date range, end	Jul. 25, 2031
DNB Capital Trust II [Member]
Debt Instrument [Line Items]
Issuance date	Mar. 30, 2005
Floating rate capital preferred securities	$ 4,000,000
LIBOR rate, borrowing period, in months	3 months
Basis spread on variable rate	1.77%
Subordinate notes bearing fixed interest rate	6.56%
Interest rate period, in years	5 years
Principal amount, floating rate junior subordinated debentures	$ 4,100,000
Maturity date range, start	May 23, 2010
Maturity date range, end	May 23, 2035