Price Risk Management Net volumes related to price risk management activities (Details) In Millions	Jun. 30, 2011	Dec. 31, 2010
Commodity contracts:
Electricity	12	9
Natural gas	82	93
Foreign currency	11	7

Name:

por_VolumeRelatedToDerivativeInstrumentsHeldAtBalanceSheetDateCommodityContractsElectricity

Namespace Prefix:

por

Data Type:

num:volumeItemType

Balance Type:

na

Period Type:

instant