Fair Value Measurements, Quantitative Information (Details) $ in Thousands	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Level 3 [Member] | Commercial Real Estate [Member] | Income Approach [Member] | Capitalization Rate [Member] | Minimum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0325
Level 3 [Member] | Commercial Real Estate [Member] | Income Approach [Member] | Capitalization Rate [Member] | Maximum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0325
Level 3 [Member] | Commercial Real Estate [Member] | Income Approach [Member] | Capitalization Rate [Member] | Weighted Average [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0325
Level 3 [Member] | Residential 1st Mortgage [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Minimum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.01
Level 3 [Member] | Residential 1st Mortgage [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Maximum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.04
Level 3 [Member] | Residential 1st Mortgage [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Weighted Average [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.03
Level 3 [Member] | Home Equity Lines and Loans [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Minimum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.01
Level 3 [Member] | Home Equity Lines and Loans [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Maximum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.02
Level 3 [Member] | Home Equity Lines and Loans [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Weighted Average [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.01
Level 3 [Member] | Commercial [Member] | Income Approach [Member] | Capitalization Rate [Member] | Minimum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0295
Level 3 [Member] | Commercial [Member] | Income Approach [Member] | Capitalization Rate [Member] | Maximum [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0870
Level 3 [Member] | Commercial [Member] | Income Approach [Member] | Capitalization Rate [Member] | Weighted Average [Member]
Quantitative Information [Abstract]
Impaired loans, measurement input	0.0340
Level 3 [Member] | Real Estate Construction [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Minimum [Member]
Quantitative Information [Abstract]
Other real estate, measurement input	0.1
Level 3 [Member] | Real Estate Construction [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Maximum [Member]
Quantitative Information [Abstract]
Other real estate, measurement input	0.1
Level 3 [Member] | Real Estate Construction [Member] | Sales Comparison Approach [Member] | Adjustment for Difference Between Comparable Sales [Member] | Weighted Average [Member]
Quantitative Information [Abstract]
Other real estate, measurement input	0.1
Nonrecurring [Member]
Quantitative Information [Abstract]
Impaired loans	$ 5,621	$ 5,181	$ 4,980
Nonrecurring [Member] | Commercial Real Estate [Member]
Quantitative Information [Abstract]
Impaired loans	2,596	2,595	2,594
Nonrecurring [Member] | Residential 1st Mortgage [Member]
Quantitative Information [Abstract]
Impaired loans	1,476	997	491
Nonrecurring [Member] | Home Equity Lines and Loans [Member]
Quantitative Information [Abstract]
Impaired loans	71	75	78
Nonrecurring [Member] | Commercial [Member]
Quantitative Information [Abstract]
Impaired loans	1,478	1,514	1,519
Nonrecurring [Member] | Level 3 [Member]
Quantitative Information [Abstract]
Impaired loans	5,621	5,181	4,980
Nonrecurring [Member] | Level 3 [Member] | Commercial Real Estate [Member]
Quantitative Information [Abstract]
Impaired loans	2,596	2,595	2,594
Nonrecurring [Member] | Level 3 [Member] | Residential 1st Mortgage [Member]
Quantitative Information [Abstract]
Impaired loans	1,476	997	491
Nonrecurring [Member] | Level 3 [Member] | Home Equity Lines and Loans [Member]
Quantitative Information [Abstract]
Impaired loans	71	75	78
Nonrecurring [Member] | Level 3 [Member] | Commercial [Member]
Quantitative Information [Abstract]
Impaired loans	1,478	$ 1,514	$ 1,519
Nonrecurring [Member] | Level 3 [Member] | Real Estate Construction [Member]
Quantitative Information [Abstract]
Other real estate	$ 873