Leases Leases (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 14
Operating Lease, Liability	44	$ 51
Operating Lease, Liability, Related to Power Purchase Agreements	25	$ 32
Lessee, Operating Lease, Lease Not yet Commenced, Estimated Present Value of Future Lease Payments	$ 30

Lessee, Operating Lease, Lease Not yet Commenced, Estimated Present Value of Future Lease Payments

No definition available.

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

- Definition

Operating Lease, Liability, Related to Power Purchase Agreements

+ References

No definition available.

+ Details

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

- Definition

The period end amount of construction work in progress at a jointly owned electricity generation plant.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-URI http://asc.fasb.org/extlink&oid=115995737&loc=d3e659983-123033

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_LeasesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant