DERIVATIVE INSTRUMENTS - Schedule of Gross Fair Value of Contracts (Details) - CL&P - Level 3 - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	$ 16.3	$ 14.7
Netting	(0.5)	(1.0)
Net Amount Recorded as a Derivative	15.8	13.7
Long-Term Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	28.8	46.9
Netting	(0.9)	(0.9)
Net Amount Recorded as a Derivative	27.9	46.0
Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(81.6)	(73.5)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	(81.6)	(73.5)
Long-Term Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(143.9)	(235.4)
Netting	0.0	0.0
Net Amount Recorded as a Derivative	$ (143.9)	$ (235.4)