REGULATORY MATTERS (Cost Recovery Mechanisms) (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2019	Feb. 28, 2019	Dec. 31, 2025	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Roll Forward]
Environmental compliance adjustor, as a percentage of total retail revenue					0.50%
Environmental compliance adjustor, return on environmental investments					$ 2	$ 3	$ 1
Purchased Power and Fuel Adjustment Clause
Regulatory Liabilities [Roll Forward]
Beginning of Period				$ 36	(17)	(9)
Deferred Fuel and Purchased Power Costs					31	2
PPFAC Refunds (Recoveries)					22	(10)
End of Period					$ 36	(17)	(9)
Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Months approved rate in effect unless modified					12 months
Renewable Energy Standard
Regulatory Liabilities [Roll Forward]
Renewable energy target percentage					9.00%
Approved spending budget	$ 55
Recovery revenue						1	1
Renewable energy actual percentage					16.00%
Renewable Energy Standard | Maximum
Regulatory Liabilities [Roll Forward]
Recovery revenue					$ 1
Renewable Energy Standard | Forecast
Regulatory Liabilities [Roll Forward]
Renewable energy target percentage			15.00%
Distributed generation requirement percent of target percentage (percentage)			30.00%
Demand Side Management
Regulatory Liabilities [Roll Forward]
Recovery revenue					$ 2	2	2
Energy Efficiency Standards
Regulatory Liabilities [Roll Forward]
Percentage of cumulative annual retail kilowatt savings, actual					19.00%
Approved recovery of spending budget		$ 23
Energy Efficiency Standards | Forecast
Regulatory Liabilities [Roll Forward]
Percentage of electric energy efficiency standards target retail savings on sales (in percentage)				22.00%
Lost Fixed Cost Recovery
Regulatory Liabilities [Roll Forward]
Recovery revenue					$ 33	$ 26	$ 22
Cap on increase in lost fixed cost recovery rate (percentage)					2.00%