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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 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	$ 5,092	$ 4,569	$ 10,134	$ 9,088
Interest cost	6,976	6,900	13,927	13,800
Expected return on plan assets	(7,900)	(6,875)	(15,800)	(13,625)
Amortization of prior service cost	0	0	0	0
Net loss recognition	2,317	2,201	4,863	4,091
Net periodic benefit cost	6,485	6,795	13,124	13,354
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	799	804	1,623	1,583
Interest cost	1,374	1,534	2,773	3,093
Expected return on plan assets	(475)	(475)	(950)	(950)
Amortization of prior service cost	(312)	(312)	(624)	(624)
Net loss recognition	1,320	1,494	2,593	2,859
Net periodic benefit cost	$ 2,706	$ 3,045	$ 5,415	$ 5,961