SEGMENT INFORMATION - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2026 USD ($) reportableSegment project
Segment Reporting Information [Line Items]
Number of wind projects \| project	3
Number of reportable segment	1
CL&P
Segment Reporting Information [Line Items]
Number of reportable segment	1
NSTAR Electric
Segment Reporting Information [Line Items]
Number of reportable segment	1
PSNH
Segment Reporting Information [Line Items]
Number of reportable segment	1
Yankee Gas, NSTAR Gas And EGMA
Segment Reporting Information [Line Items]
Natural gas transition service transaction costs \| $	$ 77.7

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-18

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration