Consolidated Statements of Comprehensive Income Consolidated Statement of Comprehensive Income Parentheticals (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Net Taxes on change in compensation retirement benefits liability and amortization	$ 2	$ (1)

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