Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (7,606)	$ (6,115)	$ (54,661)	$ (47,378)
Total other comprehensive loss	140	246	(949)	737
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	215	378	(1,461)	1,133
Income tax expense	(75)	(132)	512	(396)
Total other comprehensive loss	140	246	(949)	737
Amortization of net loss	(312)	(273)	(934)	(819)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	3,642	3,688	10,926	11,063
Adjustment due to effects of regulation	(3,115)	$ (3,037)	$ (11,453)	$ (9,111)
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)