Fair Value Accounting and Measurement Fair Value, quantitative inputs to Level 3 measurements (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans	$ 6,577	$ 3,787
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans	6,577	3,787
Other Real Estate Owned, Fair Value Disclosure	1,423	4,388
Real Estate Collateral [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans		2,248
Other Collateral [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans		$ 1,539
Not Collateral-Dependent [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans	3,058
Real Estate Collateral [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans	$ 3,519
Income Approach Valuation Technique [Member] | Minimum [Member] | Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Not Collateral-Dependent [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	3.75%	4.50%
Income Approach Valuation Technique [Member] | Maximum [Member] | Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Not Collateral-Dependent [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	7.75%	6.50%
Income Approach Valuation Technique [Member] | Weighted Average [Member] | Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Not Collateral-Dependent [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Inputs, Discount Rate	4.12%	5.26%