Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
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	$ 5,042	$ 4,519
Interest cost	6,951	6,900
Expected return on plan assets	(7,900)	(6,750)
Amortization of prior service cost	0	0
Net loss recognition	2,546	1,890
Net periodic benefit cost	6,639	6,559
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	824	779
Interest cost	1,399	1,559
Expected return on plan assets	(475)	(475)
Amortization of prior service cost	(312)	(312)
Net loss recognition	1,273	1,365
Net periodic benefit cost	$ 2,709	$ 2,916