Fair Value Measurements, Quantitative Information (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale debt securities	$ 240,426	$ 254,782
Impaired Loans [Member] | Appraised Collateral Values [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale debt securities	$ 6,281	$ 1,569
Impaired Loans [Member] | Appraised Collateral Values [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	0 months	6 months
Impaired Loans [Member] | Appraised Collateral Values [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	12 months	12 months
Impaired Loans [Member] | Appraised Collateral Values [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Holding period	11 months 21 days	11 months 4 days
Impaired Loans [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0	0
Impaired Loans [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	1	1
Impaired Loans [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.2006	0.3083
Impaired Loans [Member] | Appraised Collateral Values [Member] | Selling Costs [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.05	0.05
Impaired Loans [Member] | Appraised Collateral Values [Member] | Selling Costs [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.11	0.09
Impaired Loans [Member] | Appraised Collateral Values [Member] | Selling Costs [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.0873	0.0835
Other Real Estate Owned [Member] | Appraised Collateral Values [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale debt securities	$ 520	$ 1,024
Other Real Estate Owned [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.25	0.15
Other Real Estate Owned [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.35	0.65
Other Real Estate Owned [Member] | Appraised Collateral Values [Member] | Discount for Time Since Appraisal [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Available-for-sale, Measurement input	0.2634	0.2626