DERIVATIVE INSTRUMENTS - Schedule of Gross Fair Value of Contracts (Details) - CL&P - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Level 3 | Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management		$ 16.3
Netting		(0.5)
Net Amount Recorded as a Derivative		15.8
Level 3 | Long-Term Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management		28.8
Netting		(0.9)
Net Amount Recorded as a Derivative		27.9
Level 3 | Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management		(81.6)
Netting		0.0
Net Amount Recorded as a Derivative		(81.6)
Level 3 | Long-Term Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management		(143.9)
Netting		0.0
Net Amount Recorded as a Derivative		$ (143.9)
Level 2 | Current Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	$ 16.4
Netting	(0.5)
Net Amount Recorded as a Derivative	15.9
Level 2 | Long-Term Derivative Assets
Current and Long-Term Derivative Assets
Commodity Supply and Price Risk Management	13.6
Netting	(0.5)
Net Amount Recorded as a Derivative	13.1
Level 2 | Current Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(81.9)
Netting	0.0
Net Amount Recorded as a Derivative	(81.9)
Level 2 | Long-Term Derivative Liabilities
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(68.0)
Netting	0.0
Net Amount Recorded as a Derivative	$ (68.0)