COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) $ in Millions	Sep. 30, 2024 USD ($)
Guarantor Obligations [Line Items]
Maximum Exposure	$ 850.0
Eversource Investment LLC \| Letters of Credit
Guarantor Obligations [Line Items]
Maximum Exposure	5.3
Maximum borrowing capacity	$ 25.0
North East Offshore, Revolution Wind, LLC and South Fork Wind, LLC
Guarantor Obligations [Line Items]
Ownership interest (percent)	50.00%
Eversource Investment LLC, Eversource Investment Service Company LLC and South Fork Class B Member, LLC
Guarantor Obligations [Line Items]
Maximum Exposure	$ 1,620.0
South Fork Wind, LLC
Guarantor Obligations [Line Items]
Maximum Exposure	$ 7.1
Ownership interest (percent)	50.00%
South Fork Class B Member, LLC
Guarantor Obligations [Line Items]
Ownership interest (percent)	50.00%
Performance Guarantee \| Eversource Investment Service Company LLC
Guarantor Obligations [Line Items]
Maximum Exposure	$ 100.0
Tax Equity \| Eversource TEI LLC
Guarantor Obligations [Line Items]
Maximum Exposure	50.0
North East Offshore, LLC, Revolution Wind, LLC, and TurbineCo, LLC \| Construction-related purchase agreements with third-party contractors
Guarantor Obligations [Line Items]
Maximum Exposure	455.3
Eversource Investment LLC, Eversource Investment Service Company LLC and South Fork Class B Member, LLC \| Funding and indemnification obligations of North East Offshore LLC
Guarantor Obligations [Line Items]
Maximum Exposure	351.1
Eversource Investment LLC \| Letters Of Credit Guarantee
Guarantor Obligations [Line Items]
Maximum Exposure	5.3
Eversource TEI LLC \| South Fork Wind Tax Equity
Guarantor Obligations [Line Items]
Maximum Exposure	50.0
South Fork Wind, LLC \| Power Purchase Guarantee
Guarantor Obligations [Line Items]
Maximum Exposure	7.1
Various Eversource subsidiaries \| Surety Bond
Guarantor Obligations [Line Items]
Maximum Exposure	31.1
North East Offshore, Revolution Wind, LLC and South Fork Wind, LLC \| Performance Guarantee
Guarantor Obligations [Line Items]
Maximum Exposure	1,090.0
North East Offshore LLC \| Payment Guarantee
Guarantor Obligations [Line Items]
Maximum Exposure	$ 62.5
Percent of obligations guaranteed (in percent)	50.00%

Guarantor Obligations, Maximum Exposure, Percent Of Obligation

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
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-Topic 210
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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