SHORT-TERM AND LONG-TERM DEBT - Borrowings Outstanding and Available under the Commercial Paper Programs (Details) - USD ($) $ in Thousands |
Jun. 30, 2026 |
Dec. 31, 2025 |
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| Debt Instrument [Line Items] | ||
| Borrowings Outstanding as of | $ 393,700 | $ 1,525,445 |
| Commercial Paper | Eversource Parent Commercial Paper Program | ||
| Debt Instrument [Line Items] | ||
| Borrowings Outstanding as of | 432,000 | 1,280,000 |
| Available Borrowing Capacity as of | $ 1,568,000 | $ 720,000 |
| Weighted-average interest rate (in percent) | 4.00% | 3.98% |
| Commercial Paper | NSTAR Electric | ||
| Debt Instrument [Line Items] | ||
| Borrowings Outstanding as of | $ 63,000 | $ 245,400 |
| Available Borrowing Capacity as of | $ 587,000 | $ 404,600 |
| Weighted-average interest rate (in percent) | 3.87% | 3.87% |
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Weighted average interest rate of short-term debt outstanding calculated at point in time. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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