Derivative Instruments Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk (details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of Derivative Instruments [Abstract]
Cost of sales	$ (373,298,000)	$ (355,335,000)	$ (458,508,000)
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Changes In Fair Value As Deferred Regulatory Assets Or Liabilities In Percentage	80% or 90%
Changes In Fair Value Deferred As Income Statement For Contracts Not Qualifying For Hedge Accounting And To Other Comprehensive Income For Contracts Qualifying For Hedge Accounting	20% or 10%
Oregon PGA Deferral Percentage	90.00%	90.00%	90.00%
Derivative, Loss on Derivative	11,000,000	70,200,000.0
Unrealized Gain On Derivatives	5,400,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	7,200,000	5,600,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	2,500,000	11,400,000
Maturity Of Credit Risk Derivatives 1	March 2016
Derivative Fair Value Of Derivative Net	4,700,000	(5,800,000)
Notional Disclosures [Abstract]
Financial Derivative, Nonmonetary Notional Amount	389,225,000	395,820,000
Derivative, Nonmonetary Notional Amount	552,500,000	398,250,000
Notional Amount of Foreign Currency Derivatives	15,002,000	13,231,000
Natural Gas Commodity [Member]
Summary of Derivative Instruments [Abstract]
Cost of sales	4,985,000	(5,850,000)
Less:Amounts deferred to regulatory accounts on balance sheet	(4,964,000)	5,850,000
Total Impact On Earnings	21,000	0
Foreign Currency [Member]
Summary of Derivative Instruments [Abstract]
Total Comprehensive Income	(300,000)	65,000
Less:Amounts deferred to regulatory accounts on balance sheet	300,000	(65,000)
Total Impact On Earnings	$ 0	$ 0