Fair Values of Financial Instruments (Quantitative Information about Unobservable Inputs used in Recurring and Nonrecurring Level Three Fair Value Measurements) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Pooled Trust Preferred Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,721	$ 2,721
Valuation Technique	Discounted cash flow	Discounted cash flow
Constant prepayment rate	2.00%	2.00%
Cumulative projected prepayments	40.00%	40.00%
Pooled Trust Preferred Securities | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	7.00%	7.00%
Probability of default	1.70%	1.70%
Projected cures given deferral	0.00%	0.00%
Loss severity	29.30%	29.30%
Pooled Trust Preferred Securities | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	8.00%	8.00%
Probability of default	2.20%	2.20%
Projected cures given deferral	15.00%	15.00%
Loss severity	34.90%	34.90%
Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 591
Valuation Technique	Third party valuations
Discount to reflect realizable value		8.97%