REGULATORY MATTERS Net Changes in Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Revenue Accruals and Deferrals
Net regulatory assets as of December 31, 2019	$ 3
Net refund of 2018 revenue deferrals and accruals, including accrued interest	20
Net revenue accrual for the six months ended June 30, 2020	34
Net regulatory assets	56
Accrued interest	3	$ 9
Regulatory Liabilities [Line Items]
Accrued interest	$ 3	$ 9