Benefit Plans (Actuarial Assumptions for Benefit Obligations) (Details)	Dec. 31, 2017	Dec. 31, 2016
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.55%	3.95%
Expected long term rate of return	7.50%	7.50%
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.75%	2.75%