Risk Management Net volumes related to price risk management activities (Details) MWh in Millions, MMBTU in Millions, $ in Millions	Sep. 30, 2021 CAD ($) MWh MMBTU	Dec. 31, 2020 CAD ($) MWh MMBTU
Commodity contracts:
Electricity \| MWh	4	6
Natural gas \| MMBTU	173	137
Foreign currency \| $	$ 17	$ 19

Net volume associated with the reporting entity's derivative instruments recorded as of the balance sheet date having arisen from price risk management activities related to natural gas.

No definition available.

Name:	por_VolumeRelatedToDerivativeInstrumentsAtBalanceSheetDateCommodityContractsNaturalGas
Namespace Prefix:	por_
Data Type:	dtr-types:energyItemType
Balance Type:	na
Period Type:	instant