XML 63 R50.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Summary of Significant Accounting Policies Estimated average service lives (Details) | 12 Months Ended
--- | ---
Dec. 31, 2016
Production, excluding thermal: |
Hydro | 95
Wind | 30
Transmission | 57
Distribution | 45
General | 12

X
- Definition estimated average service life - hydro production plant + References No definition available. + Details
Name: | por_EstimatedAverageServiceLifeHydroProductionPlant
Namespace Prefix: | por_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition estimated average service life - wind production plant + References No definition available. + Details
Name: | por_EstimatedAverageServiceLifeWindProductionPlant
Namespace Prefix: | por_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition estimated average service lives - distribution plant + References No definition available. + Details
Name: | por_EstimatedAverageServiceLivesDistributionPlant
Namespace Prefix: | por_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition estimated average service lives - general plant + References No definition available. + Details
Name: | por_EstimatedAverageServiceLivesGeneralPlant
Namespace Prefix: | por_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition estimated average service lives - transmission plant + References No definition available. + Details
Name: | por_EstimatedAverageServiceLivesTransmissionPlant
Namespace Prefix: | por_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Production plant, excluding thermal: [Abstract] + References No definition available. + Details
Name: | por_ProductionExcludingThermalAbstract
Namespace Prefix: | por_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration