Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Variable Interest Entity, Cash and cash equivalents		$ 1
Variable Interest Entity, Electric utility plant, net	$ 5	$ 5

The carrying amount of the variable interest entities' electric utility plant, net included in the reporting entity's consolidated statement of financial position.

No definition available.

Name:	por_VariableInterestEntityConsolidatedCarryingAmountElectricUtilityPlantNet
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant