COMMITMENTS AND CONTINGENCIES (COMMITMENTS) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	$ 224
2018	169
2019	169
2020	148
2021	121
Thereafter	1,147
Unrecorded Unconditional Purchase Obligation	1,978
Operating Leases, Rent Expense	2	$ 3
Fuel, Including Transportation
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	100
2018	76
2019	76
2020	67
2021	43
Thereafter	269
Unrecorded Unconditional Purchase Obligation	631
Purchased Power
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	32
2018	0
2019	0
2020	0
2021	0
Thereafter	0
Unrecorded Unconditional Purchase Obligation	32
Transmission Facilities [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	18
2018	19
2019	19
2020	8
2021	4
Thereafter	10
Unrecorded Unconditional Purchase Obligation	78
Renewable Energy Power Purchase Agreement [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	64
2018	64
2019	64
2020	63
2021	63
Thereafter	730
Unrecorded Unconditional Purchase Obligation	$ 1,048
Percentage of Purchase Power Obligations	100.00%
RES Performance Based Incentives Minimum Commitment [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	$ 8
2018	8
2019	8
2020	8
2021	8
Thereafter	59
Unrecorded Unconditional Purchase Obligation	99
Contractual Rights [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	1
2018	1
2019	1
2020	1
2021	2
Thereafter	75
Unrecorded Unconditional Purchase Obligation	81
Operating Lease [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	1
2018	1
2019	1
2020	1
2021	1
Thereafter	4
Unrecorded Unconditional Purchase Obligation	$ 9