Pension and Other Post-Employment Benefits (Weighted Average Assumptions Used) (Details)	Dec. 31, 2017	Dec. 31, 2016
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.25%	3.50%
Rates of Increase in Compensation Levels	3.49%	3.49%
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.44%	3.80%
Rates of Increase in Compensation Levels	5.04%	5.04%