REGULATORY MATTERS (Cost Recovery Mechanisms) (Details) $ in Millions	1 Months Ended		12 Months Ended
	May 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Dec. 31, 2025	Dec. 31, 2020	Dec. 31, 2017 USD ($) $ / kWh	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Months approved rate in effect unless modified					12 months
Over-recovered costs for purchased power and fuel					$ 9	$ 38
Renewable Energy Standard
Public Utilities, General Disclosures [Line Items]
Renewable energy target percentage (in percentage)					7.00%
Approved spending budget	$ 54
Recovery revenue					$ 1
Renewable energy actual percentage (in percentage)					10.00%
Renewable Energy Standard | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Renewable energy target percentage (in percentage)			15.00%
Distributed generation requirement target percentage (in percentage)			30.00%
Energy Efficiency Standards
Public Utilities, General Disclosures [Line Items]
Approved spending budget		$ 22
Approved carryover of unused funds		8
Approved Recovery of Spending Budget		14
Renewable energy budget spending		$ 23
Percentage of cumulative annual retail kilowatt savings, actual (in percentage)					14.00%
Energy Efficiency Standards | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Percentage of electric energy efficiency standards target retail savings on sales (in percentage)				22.00%
Demand Side Management - Energy Efficiency Standards
Public Utilities, General Disclosures [Line Items]
Recovery revenue					$ 2		$ 3
Lost Fixed Cost Recovery Mechanism
Public Utilities, General Disclosures [Line Items]
Recovery revenue					$ 22	$ 18	$ 12
Cap on increase in lost fixed cost recovery rate (in percentage)					2.00%
March 2017 through March 2018 | Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Purchased power And fuel adjustment clause rate [cents per kwh] | $ / kWh					(0.0020)
May 2016 through February 2017 | Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Purchased power And fuel adjustment clause rate [cents per kwh] | $ / kWh					0.0015
April 2015 through April 2016 | Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Purchased power And fuel adjustment clause rate [cents per kwh] | $ / kWh					0.0068
October 2014 through March 2015 | Purchased Power and Fuel Adjustment Clause
Public Utilities, General Disclosures [Line Items]
Purchased power And fuel adjustment clause rate [cents per kwh] | $ / kWh					0.0050