Fair Value Measurements, Assets or Liabilities Measured at Fair Value on a Non-recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	$ 2,594
Significant Unobservable Inputs (Level 3) [Member] | Residential 1st Mortgage [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,485
Significant Unobservable Inputs (Level 3) [Member] | Home Equity Lines and Loans [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	72
Significant Unobservable Inputs (Level 3) [Member] | Commercial [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,490
Nonrecurring [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	5,641	$ 5,181	$ 4,703
Other Real Estate	873	873	873
Total Assets Measured at Fair Value On a Non-Recurring Basis	6,514	6,054	5,576
Nonrecurring [Member] | Commercial Real Estate [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	2,594	2,595	2,526
Nonrecurring [Member] | Residential 1st Mortgage [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,485	997	386
Nonrecurring [Member] | Home Equity Lines and Loans [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	72	75	48
Other Real Estate		0
Nonrecurring [Member] | Agricultural [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			366
Nonrecurring [Member] | Commercial [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,490	1,514	1,358
Nonrecurring [Member] | Consumer [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			19
Nonrecurring [Member] | Real Estate Construction [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Other Real Estate	873	873	873
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Other Real Estate	0	0	0
Total Assets Measured at Fair Value On a Non-Recurring Basis	0	0	0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial Real Estate [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential 1st Mortgage [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Home Equity Lines and Loans [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Other Real Estate		0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Agricultural [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Consumer [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Real Estate Construction [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Other Real Estate	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Other Real Estate	0	0	0
Total Assets Measured at Fair Value On a Non-Recurring Basis	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Commercial Real Estate [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Residential 1st Mortgage [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Home Equity Lines and Loans [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Other Real Estate		0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Agricultural [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Commercial [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Consumer [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member] | Real Estate Construction [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Other Real Estate	0	0	0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	5,641	5,181	4,703
Other Real Estate	873	873	873
Total Assets Measured at Fair Value On a Non-Recurring Basis	6,514	6,054	5,576
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	2,594	2,595	2,526
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Residential 1st Mortgage [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,485	997	386
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Home Equity Lines and Loans [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	72	75	48
Other Real Estate		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Agricultural [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			366
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans	1,490	1,514	1,358
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Consumer [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Impaired Loans			19
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Real Estate Construction [Member]
Fair Value on Non-recurring Basis by Fair Value Hierarchy [Abstract]
Other Real Estate	$ 873	$ 873	$ 873