COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) - USD ($) $ in Millions	Jan. 31, 2026	Dec. 31, 2025	Sep. 30, 2024	Dec. 31, 2023
Guarantor Obligations [Line Items]
Maximum exposure			$ 850.0
North East Offshore and Revolution Wind, LLC
Guarantor Obligations [Line Items]
Ownership interest (in percent)		50.00%
South Fork Class B Member, LLC
Guarantor Obligations [Line Items]
Ownership interest (in percent)		50.00%
Eversource Investment Services Company LLC
Guarantor Obligations [Line Items]
Maximum exposure			$ 100.0
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 (in percent)		50.00%		50.00%
Tax Equity | Eversource TEI LLC
Guarantor Obligations [Line Items]
Maximum exposure		$ 50.0
Financial Guarantee | Subsequent Event
Guarantor Obligations [Line Items]
Maximum exposure	$ 900.0
Revolution Wind, LLC and TurbineCo, LLC | Offshore wind construction-related purchase agreements with third-party contractors
Guarantor Obligations [Line Items]
Maximum exposure		127.0
Revolution Wind, LLC and TurbineCo, LLC | Performance Guarantee
Guarantor Obligations [Line Items]
Maximum exposure		693.0
Eversource Investment LLC, Eversource Investment Service Company LLC and South Fork Class B Member, LLC | Funding and Indemnification Obligations
Guarantor Obligations [Line Items]
Maximum exposure		176.7
Eversource TEI LLC | South Fork Wind Tax Equity
Guarantor Obligations [Line Items]
Maximum exposure		50.0
South Fork Wind, LLC | Power Purchase Agreement Security
Guarantor Obligations [Line Items]
Maximum exposure		7.1
Various Eversource subsidiaries | Surety Bonds
Guarantor Obligations [Line Items]
Maximum exposure		$ 34.1