FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash Equivalents		$ 55
Restricted Cash	$ 18	15
Energy Derivative Contract, Regulatory Recovery	3	10
Energy Derivative Contract, No Regulatory Recovery	3	2
Total Assets	24	82
Liabilities
Energy Derivative Contracts, Regulatory Recovery	(76)	(37)
Total Liabilities	(76)	(37)
Total Assets (Liabilities), Net	(52)	45
Level 1
Assets
Cash Equivalents		55
Restricted Cash	18	15
Energy Derivative Contract, Regulatory Recovery	0	0
Energy Derivative Contract, No Regulatory Recovery	0	0
Total Assets	18	70
Liabilities
Energy Derivative Contracts, Regulatory Recovery	0	0
Total Liabilities	0	0
Total Assets (Liabilities), Net	18	70
Level 2
Assets
Cash Equivalents		0
Restricted Cash	0	0
Energy Derivative Contract, Regulatory Recovery	3	10
Energy Derivative Contract, No Regulatory Recovery	3	0
Total Assets	6	10
Liabilities
Energy Derivative Contracts, Regulatory Recovery	(76)	(35)
Total Liabilities	(76)	(35)
Total Assets (Liabilities), Net	(70)	(25)
Level 3
Assets
Cash Equivalents		0
Restricted Cash	0	0
Energy Derivative Contract, Regulatory Recovery	0	0
Energy Derivative Contract, No Regulatory Recovery	0	2
Total Assets	0	2
Liabilities
Energy Derivative Contracts, Regulatory Recovery	0	(2)
Total Liabilities	0	(2)
Total Assets (Liabilities), Net	$ 0	$ 0