Income Tax (details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
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	(6,161)	(5,489)	20,288	21,080
Differences Required To Be Flowed Through By Regulatory Commissions	(310)	(393)	1,184	1,171
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(271)	281	(449)	(554)
Income Tax Expense (Benefit)	$ (6,742)	$ (5,601)	$ 21,023	$ 21,697
Effective Income Tax Rate	43.60%	40.50%	41.00%	40.80%