Retirement And Employee Benefit Plans (Schedule Of Assumptions Used - Benefit Obligations) (Details)	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.20%	4.60%
Rate of compensation increase	3.50%	3.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.20%	4.60%