DERIVATIVE INSTRUMENTS - Schedule of Gross Fair Value of Contracts (Details) - CL&P - Level 2 - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	$ 14.2	$ 16.4
Netting	(0.3)	(0.5)
Net Amount Recorded as a Derivative	13.9	15.9
Long-Term Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	0.0	13.6
Netting	0.0	(0.5)
Net Amount Recorded as a Derivative	0.0	13.1
Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(71.1)	(81.9)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	(71.1)	(81.9)
Long-Term Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	0.0	(68.0)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	$ 0.0	$ (68.0)

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