Benefit Plans (Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Weighted average assumptions used in net periodic benefit cost:
Discount rate	3.48%	3.99%	4.08%
Rate of compensation increase	4.01%	4.04%	4.07%
Long-term rate of return on assets	6.47%	6.95%	6.84%
Weighted average assumptions used in benefit obligations:
Discount rate	3.14%	3.68%
Rate of compensation increase	3.80%	4.04%
Other Postretirement Benefits Plan [Member]
Weighted average assumptions used in net periodic benefit cost:
Discount rate	3.90%	4.30%	3.90%
Weighted average assumptions used in benefit obligations:
Discount rate	3.45%	3.90%