Net realized and unrealized gains and losses on derivative transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commodity contracts: [Abstract]
Electricity	$ 78	$ 56	$ 117
Natural Gas	28	19	98
Realized And Unrealized Losses Net Commodity Contracts, Foreign Currency	$ 1	$ 0	$ 0

Realized and unrealized gains and losses, net on commodity contracts related to electricity not designated as hedging instruments included in purchased power and fuel expense in the statement of income.

No definition available.

Name:	por_RealizedAndUnrealizedGainsAndLossesNetCommodityContractsElectricity
Namespace Prefix:	por_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration