Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of Net Periodic Benefit Costs Capitalized to Utility Property	40.00%
Percentage of Net Periodic Benefit Costs Recorded to Operating Expenses	60.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,450	$ 5,042
Interest cost	6,466	6,951
Expected return on plan assets	(8,250)	(7,900)
Amortization of prior service cost	75	0
Net loss recognition	2,088	2,546
Net periodic benefit cost	5,829	6,639
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	804	824
Interest cost	1,197	1,399
Expected return on plan assets	(500)	(475)
Amortization of prior service cost	(815)	(312)
Net loss recognition	1,655	1,273
Net periodic benefit cost	$ 2,341	$ 2,709