Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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	$ 4,874	$ 5,450
Interest cost	7,138	6,466
Expected return on plan assets	(7,815)	(8,250)
Amortization of prior service cost	75	75
Net loss recognition	2,415	2,088
Net periodic benefit cost	6,687	5,829
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	772	804
Interest cost	1,372	1,197
Expected return on plan assets	(718)	(500)
Amortization of prior service cost	(275)	(815)
Net loss recognition	1,246	1,655
Net periodic benefit cost	$ 2,397	$ 2,341