Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Variable interest Entities [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	$ 5	$ 6
Variable Interest Entity, Consolidated, Carrying Amount, Cash and Cash Equivalents	$ 1	$ 1
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	1.00%
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	99.00%
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions	100.00%
Estimated Remaining Useful Life of Facility Acquired	75.00%

Estimated useful life expected to be remaining at the date of purchase in a future period.

No definition available.

Name:	por_EstimatedRemainingUsefulLifeOfFacilityAcquired
Namespace Prefix:	por_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

The carrying amount of the consolidated variable interest entities' cash and cash equivalents included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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

- Definition

The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsidiaryOrEquityMethodInvesteeCumulativePercentageOwnershipAfterAllTransactions
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The net carrying amount of the consolidated Variable Interest Entity's assets and liabilities included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=SL6759159-111685

+ Details

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration