Loans - Nonaccrual Loans Segregated by Class of Loan (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	$ 4,894	$ 4,811
Residential Mortgage Loans [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	2,088	2,560
Residential Mortgage Loans [Member] | 1-4 Family First Lien Residential Mortgages [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	2,088	2,560
Commercial Loans [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	2,443	1,863
Commercial Loans [Member] | Real Estate [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	1,545	1,223
Commercial Loans [Member] | Lines of Credit [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	132
Commercial Loans [Member] | Other Commercial and Industrial [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	766	640
Consumer Loans [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	363	388
Consumer Loans [Member] | Home Equity and Junior Liens [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	300	338
Consumer Loans [Member] | Other Consumer [Member]
Nonaccrual loans, Segregated by class of loans [Abstract]
Nonaccrual status loans	$ 63	$ 50