SUPPLEMENTARY INFORMATION Schedule of Pass Through Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Operating Expenses [Line Items]
Plant operating expense	$ 340	$ 354	$ 701	$ 713
Pass through costs [Member]
Other Operating Expenses [Line Items]
Plant operating expense	$ 10	$ 12	$ 23	$ 25