SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 1,602.0	$ 1,602.0
Total intangible assets, gross	440.0	440.0
Accumulated amortization	(148.0)	(122.0)
Intangible Assets, Net (Excluding Goodwill), Total	292.0	318.0
Intangible assets amortization expense	26.0	26.0	$ 26.0
Amortization recorded against revenues	13.5	13.5	$ 13.5
Expected amortization, year one	26.0
Expected amortization, year two	26.0
Expected amortization, year three	26.0
Expected amortization, year four	26.0
Expected amortization, year five	26.0
Expected amortization expense, recorded against revenues, year one	13.5
Expected amortization expense, recorded against revenues, year two	13.5
Expected amortization expense, recorded against revenues, year three	13.5
Expected amortization expense, recorded against revenues, year four	13.5
Expected amortization expense, recorded against revenues, year five	13.5
Renewable energy transmission and consumption permits
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	169.0	169.0
Accumulated amortization	$ (68.0)	(59.0)
Renewable energy transmission and consumption permits | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period	15 years
Renewable energy transmission and consumption permits | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period	19 years
O&M agreement
Finite-Lived Intangible Assets [Line Items]
Amortization period	23 years
Intangible assets, gross	$ 66.0	66.0
Accumulated amortization	$ (20.0)	(17.0)
ESJ PPA
Finite-Lived Intangible Assets [Line Items]
Amortization period	14 years
Intangible assets, gross	$ 190.0	190.0
Accumulated amortization	(51.0)	(37.0)
Other
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	15.0	15.0
Accumulated amortization	$ (9.0)	$ (9.0)
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years