Long term debt (Tables)

12 Months Ended

Dec. 31, 2017

Long-term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments [Table Text Block]

Long-term debt consists of the following (in millions):

	As of December 31,
	2017			2016
First Mortgage Bonds, rates range from 2.51% to 9.31%, with a weighted average rate of 5.03% in 2017 and 4.86% in 2016, due at various dates through 2048	$	2,315		$	2,090
Unsecured term bank loans, variable rates of approximately 1.87%at 11/27/2017 and 1.37% at 12/31/2016	—			150
Pollution Control Revenue Bonds, 5% rate, due 2033	142			142
Pollution Control Revenue Bonds owned by PGE	(21		)	(21		)
Total long-term debt	2,436			2,361
Less: Unamortized debt expense	(10		)	(11		)
Less: Current portion of long-term debt	—			(150		)
Long-term debt, net of current portion	$	2,426		$	2,200

Schedule of Maturities of Long-term Debt [Table Text Block]

As of December 31, 2017, the future minimum principal payments on long-term debt are as follows (in millions):

Years ending December 31:
2018	$	—
2019	300
2020	—
2021	160
2022	—
Thereafter	1,976
	$	2,436