Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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	$ 5,450	$ 5,092	$ 10,900	$ 10,134
Interest cost	6,466	6,976	12,932	13,927
Expected return on plan assets	(8,250)	(7,900)	(16,500)	(15,800)
Amortization of prior service cost	75	0	150	0
Net loss recognition	1,842	2,317	3,930	4,863
Net periodic benefit cost	5,583	6,485	11,412	13,124
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	804	799	1,608	1,623
Interest cost	1,197	1,374	2,394	2,773
Expected return on plan assets	(500)	(475)	(1,000)	(950)
Amortization of prior service cost	209	(312)	(606)	(624)
Net loss recognition	562	1,320	2,217	2,593
Net periodic benefit cost	$ 2,272	$ 2,706	$ 4,613	$ 5,415