Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of Net Periodic Benefit Costs Capitalized to Utility Property	40.00%
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	$ (10,259)	$ (7,866)
Percentage of Net Periodic Benefit Costs Recorded to Operating Expenses	60.00%
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	$ 9,078	7,587
Service cost	19,755	21,614	$ 20,406
Interest cost	28,417	26,096	27,898
Expected return on plan assets	(31,763)	(33,018)	(31,626)
Amortization of prior service cost	257	257	2
Net loss recognition	10,216	7,879	9,793
Net periodic benefit cost	26,882	22,828	26,473
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax	1,181	279
Service cost	3,006	3,188	3,220
Interest cost	5,598	4,831	5,490
Expected return on plan assets	(2,101)	(1,973)	(1,899)
Amortization of prior service cost	(981)	(1,089)	(1,144)
Net loss recognition	4,013	4,232	4,934
Net periodic benefit cost	$ 9,535	$ 9,189	$ 10,601