Fair Values of Financial Instruments (Quantitative Information about Unobservable Inputs used in Recurring and Nonrecurring Level Three Fair Value Measurements) (Details) - Pooled Trust Preferred Securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,721	$ 2,588
Valuation Technique	Discounted cash flow	Discounted cash flow
Constant prepayment rate	2.00%	2.00%
Cumulative projected prepayments	40.00%	40.00%
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%	32.50%
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%	38.70%