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INCOME TAXES - Narrative (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Operating Loss Carryforwards [Line Items] |  |  |
Interest expense on uncertain tax positions | $ 1,300,000 | $ 300,000 | $ 0
Accrued interest payable | 1,700,000 | 400,000 |
State and Local Jurisdiction |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance for tax credit and operating loss carryforward | 558,200,000 | 104,100,000 |
State and Local Jurisdiction | CL&P |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Change in valuation allowance | 23,500,000 | 17,300,000 |
Eversource | State and Local Jurisdiction |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Change in valuation allowance | $ 27,300,000 | $ 21,300,000 |

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- Definition The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15 + Details
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