Benefit Plans (Net Pension and Postretirement Cost Weighted-Average Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - service cost	1.68%	1.81%	2.04%
Discount rate - interest cost	1.27%	1.81%	2.04%
Expected rate of return on plan assets	4.80%	5.36%	5.38%
Rate of compensation increase	1.68%	2.03%	2.12%
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - service cost	3.68%	4.45%	4.20%
Discount rate - interest cost	3.68%	4.45%	4.20%
Health care cost trend rate	7.15%	6.23%	6.62%