Price Risk Management Counterparties Representing 10% or More of Assets and Liabilities from price risk management activities (Details)	Mar. 31, 2016	Dec. 31, 2015
Assets from price risk management activities:
Counterparty A	48.00%	59.00%
Counterparty B	11.00%	8.00%
Counterparty C	9.00%	10.00%
Total	68.00%	77.00%
Liabilities from price risk management activities:
Counterparty D	38.00%	36.00%
Counterparty B	10.00%	10.00%
Counterparty E	9.00%	10.00%
Total	57.00%	56.00%

Assets from price risk management activities: [Abstract]

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- Definition

Represents aggregate of individually significant counterparties of total assets arising from derivative instruments from price risk management activities.

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No definition available.

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- Definition

Represents aggregate of individually significant counterparties of total liabilities arising from derivative instruments from price risk management activities.

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- Definition

Individually significant counterparty of total assets arising from derivative instruments from price risk management activities.

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No definition available.

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Name:	por_CounterpartyA
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- Definition

Individually significant counterparty of total assets arising from derivative instruments from price risk management activities.

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No definition available.

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- Definition

Individually significant counterparty of total liabilities arising from derivative instruments from price risk management activities.

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- Definition

Individually significant counterparty of total assets arising from derivative instruments from price risk management activities.

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No definition available.

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- Definition

Counterparty D for PRM Liab

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- Definition

Counterparty E For PRM Liab

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- Definition

Liabilities from price risk management activities: [Abstract]

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