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Commitments and Guarantees Schdule of Long term contracts for purchase of electric power (Details)
$ in Millions
 12 Months Ended
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