Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income Parentheticals $ in Millions	12 Months Ended
Dec. 31, 2014 USD ($)
Net Taxes on change in compensation retirement benefits liability and amortization	$ 2

Net Taxes on change in compensation retirement benefits liability and amortization

No definition available.

Name:	por_NetTaxesOnChangeInCompensationRetirementBenefitsLiabilityAndAmortization
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration