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INCOME TAXES - Narrative (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Operating Loss Carryforwards [Line Items] |  |  |
Interest expense on uncertain tax positions | $ 300,000 | $ 0 | $ 0
Accrued interest payable | 400,000 | 100,000 |
State and Local Jurisdiction |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance for tax credit and operating loss carryforward | 104,100,000 | 82,800,000 |
State and Local Jurisdiction | CL&P |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Change in valuation allowance | 17,300,000 | 18,800,000 |
Eversource | State and Local Jurisdiction |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Change in valuation allowance | $ 21,300,000 | $ 21,300,000 |

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- Definition Amount of valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from tax credit carryforwards and operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized. + References No definition available. + Details
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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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- Definition Amount of interest expense for an underpayment of income taxes. + 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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