DERIVATIVE INSTRUMENTS - Summary of Level 3 Derivative Contracts and Significant Unobservable Inputs Used (Details) - CL&P - Forward Reserve Prices - Level 3 - $ / KWmo	Mar. 31, 2022	Dec. 31, 2021
Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.50	0.50
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	1.15	1.15
Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.82	0.82