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, 2018	Dec. 31, 2017
Assets
Cash Equivalents	$ 125	$ 30
Restricted Cash	15	12
Energy Derivative Contract, Regulatory Recovery	10	9
Energy Derivative Contract, No Regulatory Recovery	2	3
Total Assets	152	54
Liabilities
Energy Derivative Contracts, Regulatory Recovery	(37)	(26)
Energy Derivative Contracts, No Regulatory Recovery		(1)
Interest Rate Swap		(1)
Total Liabilities	(37)	(28)
Net Total Assets (Liabilities)	115	26
Level 1
Assets
Cash Equivalents	125	30
Restricted Cash	15	12
Energy Derivative Contract, Regulatory Recovery	0	0
Energy Derivative Contract, No Regulatory Recovery	0	0
Total Assets	140	42
Liabilities
Energy Derivative Contracts, Regulatory Recovery	0	0
Energy Derivative Contracts, No Regulatory Recovery		0
Interest Rate Swap		0
Total Liabilities	0	0
Net Total Assets (Liabilities)	140	42
Level 2
Assets
Cash Equivalents	0	0
Restricted Cash	0	0
Energy Derivative Contract, Regulatory Recovery	10	9
Energy Derivative Contract, No Regulatory Recovery	0	0
Total Assets	10	9
Liabilities
Energy Derivative Contracts, Regulatory Recovery	(35)	(26)
Energy Derivative Contracts, No Regulatory Recovery		0
Interest Rate Swap		(1)
Total Liabilities	(35)	(27)
Net Total Assets (Liabilities)	(25)	(18)
Level 3
Assets
Cash Equivalents	0	0
Restricted Cash	0	0
Energy Derivative Contract, Regulatory Recovery	0	0
Energy Derivative Contract, No Regulatory Recovery	2	3
Total Assets	2	3
Liabilities
Energy Derivative Contracts, Regulatory Recovery	(2)	0
Energy Derivative Contracts, No Regulatory Recovery		(1)
Interest Rate Swap		0
Total Liabilities	(2)	(1)
Net Total Assets (Liabilities)	$ 0	$ 2