Fair Value (Reconciliation of all Assets Measured at Fair Value on Recurring Basis, Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Obligations of State and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or Losses Included in Other Comprehensive Income	$ 0	$ 0	$ 34	$ 38
Fair Value, Measurements, Recurring | Obligations of State and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of Recurring Level 3 Assets at July 1	6,192	7,942	7,023	8,749
Total Gains or Losses Included in Other Comprehensive Income	0	0	34	38
Maturities / Calls	(450)	(555)	(1,315)	(1,400)
Purchases	0	0	0	0
Balance of Recurring Level 3 Assets at September 30	5,742	7,387	5,742	7,387
Fair Value, Measurements, Recurring | Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of Recurring Level 3 Assets at July 1	353	353	353	353
Total Gains or Losses Included in Other Comprehensive Income	0	0	0	0
Maturities / Calls	0	0	0	0
Purchases	0	0	0	0
Balance of Recurring Level 3 Assets at September 30	$ 353	$ 353	$ 353	$ 353