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Basis of Presentation (Details) retail_customers in Thousands, mi² in Thousands | Mar. 31, 2021 mi² retail_customers
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Basis of Presentation [Abstract] |
Service Area Sq Miles | mi² | 4
Incorporated Cities | 51
Number of Retail Customers | retail_customers | 909

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- Definition Basis of Presentation [Abstract] + References No definition available. + Details
Name: | por_BasisOfPresentationAbstract
Namespace Prefix: | por_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of incorporated cities in service area. + References No definition available. + Details
Name: | por_IncorporatedCities
Namespace Prefix: | por_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Includes residential, commercial and industrial. + References No definition available. + Details
Name: | por_NumberOfRetailCustomers
Namespace Prefix: | por_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Approximate square miles of service area. + References No definition available. + Details
Name: | por_ServiceAreaSqMiles
Namespace Prefix: | por_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant