Long term debt (Details) - USD ($) $ in Millions	1 Months Ended		2 Months Ended	3 Months Ended			6 Months Ended	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Feb. 29, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2016	Jan. 29, 2016	May. 19, 2015
Debt Instrument [Line Items]
Proceeds from Issuance of First Mortgage Bond									$ 145
Repayments of Debt		$ 70		$ 55	$ 67	$ 50	$ 200		442
Long-term Pollution Control Bond									21
Debt Instrument, Interest Rate, Stated Percentage		3.55%			6.80%	3.46%	6.80%							3.50%
Proceeds from Issuance of Long-term Debt					$ 70	$ 75			145	$ 585	$ 380
Unsecured Debt, Current									$ 0	$ 305
First mortgage Bonds - minimum rate									3.46%
First Mortgage Bonds - maximum rate									9.31%
Debt, Weighted Average Interest Rate									5.29%	5.42%
Unsecured term bank loan rate - minimum									0.86%
Unsecured term bank loan rate - maximum									0.93%
Pollution Control Revenue Bonds owned by PGE									$ 21	$ 21
Long-term Pollution Control Bond, Rate									5.00%
Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Debt	$ 133		$ 58					$ 75
Debt Instrument, Interest Rate, Stated Percentage	2.51%											5.80%	3.81%
Proceeds from Issuance of Long-term Debt	$ 140