Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Expense [Abstract]
Income tax charge from increased effective Oregon tax rate			$ 600
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 1,429	$ 728	20,321	$ 26,449
Differences Required To Be Flowed Through By Regulatory Commissions	85	61	1,414	1,494
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(100)	(9)	(1,238)	(178)
Income Tax Expense (Benefit)	$ 1,414	$ 780	$ 20,497	$ 27,765
Effective Income Tax Rate	39.20%	42.10%	40.00%	41.60%