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Commitments and Guarantees Schdule of Long term contracts for purchase of electric power (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($) MW | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Priest Rapids and Wanapum [Member] |  |  |
Long-term Contract for Purchase of Electric Power [Line Items] |  |  |
Revenue Bonds issued by the Public Utility Districts | $ 1,269 |  |
PGE Share of Output | 8.60% |  |
PGE Share of Capacity | MW | 163 |  |
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration | Dec. 31, 2052 |  |
commitment costs | $ 16 | $ 16 | $ 18
Wells [Member] |  |  |
Long-term Contract for Purchase of Electric Power [Line Items] |  |  |
Revenue Bonds issued by the Public Utility Districts | $ 160 |  |
PGE Share of Output | 19.40% |  |
PGE Share of Capacity | MW | 150 |  |
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration | Aug. 31, 2018 |  |
commitment costs | $ 11 | 10 | 10
Portland Hydro [Member] |  |  |
Long-term Contract for Purchase of Electric Power [Line Items] |  |  |
Revenue Bonds issued by the Public Utility Districts | $ 0 |  |
PGE Share of Output | 0.00% |  |
PGE Share of Capacity | MW | 0 |  |
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration | Jun. 30, 2017 |  |
commitment costs | $ 1 | $ 1 | $ 2

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- Definition Date of contract expiration of long-term contract to purchase electricity from a production plant, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 + Details
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