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DERIVATIVE INSTRUMENTS - Narrative (Details) - MW | 3 Months Ended |
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Mar. 31, 2023 | Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of costs or benefits borne under capacity-related contracts by United Illuminated Company | 20.00% |
Amount of power to be purchased under capacity-related contract (in MW) | 674 | 674
Level 3 | Minimum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts | 2.30% |
Level 3 | Maximum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts | 6.60% |
Level 3 | Weighted Average |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts | 5.50% |
CL&P |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of costs or benefits borne under capacity-related contracts | 80.00% |

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