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COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2025 USD ($) letterOfCredit | Sep. 30, 2024 USD ($)
Guarantor Obligations [Line Items] |  |
Maximum Exposure |  | $ 850.0
Number of letters of credit | letterOfCredit | 2 |
Eversource Investment LLC | Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | $ 4.3 |
Maximum borrowing capacity | $ 25.0 |
North East Offshore, Revolution Wind, LLC and South Fork Wind, LLC |  |
Guarantor Obligations [Line Items] |  |
Ownership interest (percent) | 50.00% |
South Fork Class B Member, LLC |  |
Guarantor Obligations [Line Items] |  |
Ownership interest (percent) | 50.00% |
Eversource Investment LLC, Eversource Investment Service Company LLC and South Fork Class B Member, LLC |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | $ 1,620.0 |
South Fork Wind, LLC |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | $ 7.1 |
Ownership interest (percent) | 50.00% |
Performance Guarantee | Eversource Investment Service Company LLC |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | $ 100.0 |
Tax Equity | Eversource TEI LLC |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 50.0 |
Revolution Wind, LLC and TurbineCo, LLC | Construction-related purchase agreements with third-party contractors |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 268.9 |
Eversource Investment LLC, Eversource Investment Service Company LLC and South Fork Class B Member, LLC | Funding and indemnification obligations of North East Offshore LLC |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 276.8 |
Eversource Investment LLC | Letters Of Credit Guarantee |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 4.3 |
Eversource TEI LLC | South Fork Wind Tax Equity |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 50.0 |
South Fork Wind, LLC | Power Purchase Guarantee |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 7.1 |
Various Eversource subsidiaries | Surety Bond |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | 34.1 |
North East Offshore, Revolution Wind, LLC, TurbineCo, LLC | Performance Guarantee |  |
Guarantor Obligations [Line Items] |  |
Maximum Exposure | $ 800.9 |

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