DERIVATIVE INSTRUMENTS - Gross Fair Values and Net Amounts of Contracts (Details) - NSTAR Electric - Level 3 - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
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| Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent | ||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Long-Term Derivative Liabilities | $ (390.3) | $ (753.1) |
| Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent | ||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Current Derivative Assets | $ 115.1 | $ 91.0 |
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- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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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/exampleRef
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