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Contingencies (Details) (USD $) | 3 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2012 | Dec. 31, 2008 | Dec. 31, 2007 | Dec. 31, 2005 | Dec. 31, 1997 | Sep. 30, 2008 | Dec. 31, 2003 | Dec. 31, 1993
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
investment in Trojan |  |  |  |  |  |  |  | 87.00%
Refund to customers for Trojan Investment including interest |  |  |  |  |  | $ 33,100,000 |  |
Class action damages sought |  |  |  |  |  |  | 260,000,000 |
Site Contingency, Names of Other Potentially Responsible Parties | 100 |  | 6 | 14 | 69 |  |  |
Low estimate of range of cost of Portland Harbor cleanup in total | 169,000,000 |  |  |  |  |  |  |
Upper estimated range of total cost of Portland harbor cleanup | 1,800,000,000 |  |  |  |  |  |  |
Repayments of Pollution Control Bond |  | $ 5,800,000 |  |  |  |  |  |

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- Definition Class action damages sought by plaintiffs against the Company in regard to return on its investment in Trojan. + References No definition available. + Details
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- Definition The portion of the Company's remaining investment in its Trojan plant that the OPUC allowed the Company to recover. + References No definition available. + Details
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- Definition Lower end estimate of the range of cost of Portland Harbor cleanup, in total. This represents the cost to all parties, not PGE portion. + References No definition available. + Details
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- Definition The cash outflow from settlement of a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 + Details
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- Definition Names of other potentially responsible parties for an individual site. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 96-1 -Paragraph 163 -Subparagraph e -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(3) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 + Details
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