Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Percentage of Service Related Net Periodic Benefit Costs Capitalized to Utility Property	40.00%
Percentage of Service Related Net Periodic Benefit Costs Recorded to Operating Expenses	60.00%
Percentage of Non-service Related Net Periodic Benefit Costs Capitalized to Regulatory Assets	40.00%
Percentage of Non-service Related Net Periodic Benefit Costs Recorded to Other Expense	60.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,546	$ 4,874
Interest cost	6,971	7,138
Expected return on plan assets	(9,125)	(7,815)
Amortization of prior service cost	75	75
Net loss recognition	1,654	2,415
Net periodic benefit cost	5,121	6,687
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	979	772
Interest cost	1,515	1,372
Expected return on plan assets	(630)	(718)
Amortization of prior service cost	(275)	(275)
Net loss recognition	1,243	1,246
Net periodic benefit cost	$ 2,832	$ 2,397