Other Postretirement Employee Benefit Plans (Weighted Average Assumptions Used To Determine Benefit Obligations) (Details) - Other postretirement benefits	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.50%	3.90%
Medical trend rate - initial	6.30%	6.50%
Medical trend rate - grading period	20 years	21 years
Medical trend rate - ultimate	4.50%	4.50%