FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash Equivalents	$ 23	$ 33
Restricted Cash	7	4
Energy Derivative Contract Assets - Regulatory Recovery	3	1
Energy Derivative Contract Assets - No Regulatory Recovery	2	1
Total Assets	35	39
Liabilities
Energy Derivative Contract Liabilities - Regulatory Recovery	(3)	(13)
Interest Rate Swap	(2)	(3)
Total Liabilities	(5)	(16)
Net Total Assets (Liabilities)	30	23
Level 1 [Member]
Assets
Cash Equivalents	23	33
Restricted Cash	7	4
Energy Derivative Contract Assets - Regulatory Recovery	0	0
Energy Derivative Contract Assets - No Regulatory Recovery	0	0
Total Assets	30	37
Liabilities
Energy Derivative Contract Liabilities - Regulatory Recovery	0	0
Interest Rate Swap	0	0
Total Liabilities	0	0
Net Total Assets (Liabilities)	30	37
Level 2 [Member]
Assets
Cash Equivalents	0	0
Restricted Cash	0	0
Energy Derivative Contract Assets - Regulatory Recovery	3	1
Energy Derivative Contract Assets - No Regulatory Recovery	0	0
Total Assets	3	1
Liabilities
Energy Derivative Contract Liabilities - Regulatory Recovery	(2)	(10)
Interest Rate Swap	(2)	(3)
Total Liabilities	(4)	(13)
Net Total Assets (Liabilities)	(1)	(12)
Level 3 [Member]
Assets
Cash Equivalents	0	0
Restricted Cash	0	0
Energy Derivative Contract Assets - Regulatory Recovery	0	0
Energy Derivative Contract Assets - No Regulatory Recovery	2	1
Total Assets	2	1
Liabilities
Energy Derivative Contract Liabilities - Regulatory Recovery	(1)	(3)
Interest Rate Swap	0	0
Total Liabilities	(1)	(3)
Net Total Assets (Liabilities)	$ 1	$ (2)