DERIVATIVE INSTRUMENTS - Gross Fair Values and Net Amounts of Contracts (Details) - CL&P - Level 2 - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Current Derivative Assets
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 15.5	$ 16.4
Netting	(0.4)	(0.5)
Net Amount Recorded as a Derivative	15.1	15.9
Long-Term Derivative Assets
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	6.2	13.6
Netting	(0.2)	(0.5)
Net Amount Recorded as a Derivative	6.0	13.1
Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(77.4)	(81.9)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	(77.4)	(81.9)
Long-Term Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(31.1)	(68.0)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	$ (31.1)	$ (68.0)

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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