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Jointly-owned Plant Jointly Owned Plant (Details) (USD $) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2013 | Sep. 30, 2013 | Dec. 31, 1985
Property, Plant and Equipment [Line Items] |  |  |
Jointly Owned Utility Plant, Proportionate Ownership Share of Boardman transferred | 15.00% |  | 15.00%
Asset Retirement Obligation Increase related to Boardman plant | $ 7,000,000 |  |
Interest in Pacific Northwest Intertie |  |  | 10.714%
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds | $ 1 |  |
Jointly Owned Utility Plant, Proportionate Ownership Share of Boardman | 80.00% | 65.00% |

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- Definition Asset Retirement Obligation Increase related to Boardman plant due to updated decommissioning study. + References No definition available. + Details
Name: | por_AssetRetirementObligationIncreaseRelatedToBoardmanPlant
Namespace Prefix: | por_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

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- Definition Interest in Pacific Northwest Intertie + References No definition available. + Details
Name: | por_InterestinPacificNorthwestIntertie
Namespace Prefix: | por_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The proportionate share of the reporting entity's interest (percent) in Boardman, a jointly owned utility plant. + References No definition available. + Details
Name: | por_JointlyOwnedUtilityPlantProportionateOwnershipShareOfBoardman
Namespace Prefix: | por_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Jointly Owned Utility Plant, Proportionate Ownership Share of Boardman transferred + References No definition available. + Details
Name: | por_JointlyOwnedUtilityPlantProportionateOwnershipShareofBoardmantransferred
Namespace Prefix: | por_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The value of all consideration given or received by the Entity in the significant acquisition or disposal. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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