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DERIVATIVE INSTRUMENTS - Narrative (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2023 MW | Dec. 31, 2022 $ / KWmo MW
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of costs or benefits borne under capacity-related contracts by United Illuminated Company (in percent) | 20.00% |
Amount of power to be purchased under capacity-related contract (in MW) | MW | 674 | 674
Level 3 | Minimum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts (in percentage) | 1.30% |
Level 3 | Maximum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts (in percentage) | 5.50% |
Level 3 | Weighted Average |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of exit price premiums related to derivative contracts (in percentage) | 4.50% |
CL&P |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Percentage of costs or benefits borne under capacity-related contracts (in percent) | 80.00% |
CL&P | Level 3 | Minimum | Measurement Input, Forward Reserve |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Derivative measurement input |  | 0.44
CL&P | Level 3 | Maximum | Measurement Input, Forward Reserve |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Derivative measurement input |  | 0.50
CL&P | Level 3 | Weighted Average | Measurement Input, Forward Reserve |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Derivative measurement input |  | 0.47

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- Definition Value of input used to measure net derivative asset (liability). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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