Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 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	$ 5,318	$ 5,092	$ 16,218	$ 15,226
Interest cost	6,634	6,976	19,566	20,903
Expected return on plan assets	(8,101)	(7,900)	(24,601)	(23,700)
Amortization of prior service cost	71	0	221	0
Net loss recognition	1,761	2,517	5,691	7,380
Net periodic benefit cost	5,683	6,685	17,095	19,809
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	815	799	2,423	2,422
Interest cost	1,261	1,374	3,655	4,147
Expected return on plan assets	(550)	(475)	(1,550)	(1,425)
Amortization of prior service cost	(299)	(274)	(905)	(898)
Net loss recognition	1,044	1,168	3,261	3,761
Net periodic benefit cost	$ 2,271	$ 2,592	$ 6,884	$ 8,007