Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (33,344)	$ (30,345)
Total other comprehensive loss	183	(1,229)
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)
Amortization of net loss	3,638	3,642
Adjustment due to effects of regulation	(3,058)	(5,223)
Total before tax	281	(1,892)
Income tax expense	(98)	663
Total other comprehensive loss	$ 183	(1,229)
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)