Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (13,051)	$ (16,710)	$ (46,395)	$ (47,055)
Total other comprehensive loss	183	140	366	(1,089)
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	(299)	(311)	(598)	(622)
Amortization of net loss	3,638	3,642	7,276	7,284
Adjustment due to effects of regulation	(3,057)	(3,115)	(6,115)	(8,338)
Total before tax	282	216	563	(1,676)
Income tax expense	(99)	(76)	(197)	587
Total other comprehensive loss	$ 183	140	$ 366	$ (1,089)
OREGON | Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Adjustment due to effects of regulation		$ (2,100)