Balance Sheet Components Other Current Assets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Other Current Assets [Line Items]
Prepaid expenses	$ 58	$ 39
Current deferred income tax asset	33us-gaap_DeferredTaxAssetsNetCurrent	33us-gaap_DeferredTaxAssetsNetCurrent
Margin deposits	20us-gaap_MarginDepositAssets	11us-gaap_MarginDepositAssets
Accrued sales tax refund related to Tucannon River Wind Farm	11por_Accruedsalestaxrefund	23por_Accruedsalestaxrefund
Assets from price risk management activities	7	6
Other	4us-gaap_OtherAssets	3us-gaap_OtherAssets
Other current assets	$ 133us-gaap_OtherAssetsCurrent	$ 115us-gaap_OtherAssetsCurrent

Accrued sales tax refund related to wind farm.

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- Definition

Regulatory assets from price risk management activities

+ References

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- Definition

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards expected to be realized or consumed within one year or operating cycle, if longer.

+ References

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

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The aggregate carrying amounts, as of the balance sheet date, of assets not separately disclosed in the balance sheet.

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Aggregate carrying amount, as of the balance sheet date, of current assets not separately disclosed in the balance sheet. Current assets are expected to be realized or consumed within one year (or the normal operating cycle, if longer).

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Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.

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