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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
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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

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