SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 1,602	$ 1,602
Total intangible assets, gross	250	250
Accumulated amortization	(37)	(26)
Other intangible assets	213	224
Intangible assets amortization expense	11	16	$ 18
Future intangible asset amortization expense per year	$ 12
Renewable energy and consumption permit [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period	19 years
Intangible assets, gross	$ 154	154
Accumulated amortization	$ (24)	(16)
O&M agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period	23 years
Intangible assets, gross	$ 66	66
Accumulated amortization	(6)	(3)
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	30	30
Accumulated amortization	$ (7)	$ (7)
Other [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years