Basis of Accounting and Consolidation Basis of Accounting and Consolidation (Stock Plans) (Details) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares to be issued in stock incentive plan (in shares)	149,983
Employee Stock Purchase Plan [Abstract]
Employee Discount for Employee Stock Purchase Plan	5.00%
Employee Stock Purchase Plan, Number Of Shares Authorized	600,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock awarded in SI plan (in shares)	13,250
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock awarded in SI plan (in shares)	15,450	18,391