Name:	por_CommodityContractAssetCurrentElectricity
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Carrying amount as of the balance sheet date of the asset arising from commodity contracts related to natural gas which are expected to be settled within a year or normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractAssetCurrentNaturalGas
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Carrying amount as of the balance sheet date of the asset arising from commodity contracts related to electricity which are expected to be settled after a year or beyond the normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractAssetNoncurrentElectricity
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Carrying amount as of the balance sheet date of the asset arising from commodity contracts related to natural gas which are expected to be settled after a year or beyond the normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractAssetNoncurrentNaturalGas
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Carrying amount as of the balance sheet date of the liability arising from commodity contracts related to electricity which are expected to be settled within a year or the normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractLiabilityCurrentElectricity
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Carrying amount as of the balance sheet date of the liability arising from the commodity contracts related to natural gas which are expected to be settled within a year or normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractLiabilityCurrentNaturalGas
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Carrying amount as of the balance sheet date of the liability arising from commodity contracts related to electricity which are expected to be settled after a year or beyond the normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractLiabilityNoncurrentElectricity
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Carrying amount as of the balance sheet date of the liability arising from commodity contracts related to natural gas which are expected to be settled after a year or beyond the normal operating cycle, if longer.

No definition available.

Name:	por_CommodityContractLiabilityNoncurrentNaturalGas
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Commodity contracts: [Abstract]

No definition available.

Name:	por_CurrentAssetsCommodityContractsAbstract
Namespace Prefix:	por_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair valules as of the balance sheet date for all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, and which are expected to be settled within one year or the normal operating cycle, if longer.

No definition available.

Name:	por_CurrentDerivativeAssets
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair values as of the balance sheet date for all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, and which are expected to be settled within one year of the normal operating cycle, if longer.

No definition available.

Name:	por_CurrentDerivativeLiabilities
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Current Liabilities, Commodity Contracts: [Abstract]

No definition available.

Name:	por_CurrentLiabilitiesCommodityContractsAbstract
Namespace Prefix:	por_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments.

No definition available.

Name:	por_DerivativeAssetsTotal
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

No definition available.

Name:	por_DerivativeLiabilitiesTotal
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Noncurrent Assets, Commodity Contracts: [Abstract]

No definition available.

Name:	por_NoncurrentAssetsCommodityContractsAbstract
Namespace Prefix:	por_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair values as of the balance sheet date for all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, and which are expected to be settled after one year or normal operating cycle, if longer.

No definition available.

Name:	por_NoncurrentDerivativeLiabilities
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Noncurrent Liabilities, Commodity Contracts: [Abstract]

No definition available.

Name:	por_NoncurrentLiabilitiesCommodityContractsAbstract
Namespace Prefix:	por_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Name:	us-gaap_DerivativeAssetsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Fair value as of the balance sheet date of all price risk derivative assets not designated as hedging instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

Name:	us-gaap_PriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value as of the balance sheet date of all price risk derivative liabilities not designated as hedging instruments.