LONG-TERM DEBT - Schedule of Long-Term Debt Issuance and Repayments (Details) - USD ($) $ in Millions	1 Months Ended
	Dec. 31, 2025	Nov. 30, 2025	Oct. 31, 2025	Sep. 30, 2025	Aug. 31, 2025	Jul. 31, 2025	Jun. 30, 2025	May 31, 2025	Feb. 28, 2025	Jan. 31, 2025
CL&P 2025 Series A First Mortgage Bonds | First Mortgage | CL&P
Debt Instrument [Line Items]
Interest Rate										4.95%
Issuance										$ 400.0
CL&P 2020 Series A First Mortgage Bonds | First Mortgage | CL&P
Debt Instrument [Line Items]
Interest Rate	0.75%
Repayments of Debt	$ (400.0)
NSTAR Electric Debentures | Unsecured Debt | NSTAR Electric
Debt Instrument [Line Items]
Interest Rate									4.85%
Issuance									$ 400.0
Short-term debt, paid									3.25%
NSTAR Electric Debentures | Unsecured Debt | NSTAR Electric
Debt Instrument [Line Items]
Interest Rate			5.20%						5.20%
Issuance			$ 300.0						$ 400.0
Short-term debt, paid									3.25%
NSTAR Electric Debentures 3.25% | Unsecured Debt | NSTAR Electric
Debt Instrument [Line Items]
Interest Rate		3.25%
Repayments of Debt		$ (250.0)
PSNH Series Y First Mortgage Bonds | First Mortgage | PSNH
Debt Instrument [Line Items]
Interest Rate							4.40%
Issuance							$ 300.0
Eversource Parent Series HH Senior Notes | Senior Notes | Eversource Parent | Eversource
Debt Instrument [Line Items]
Interest Rate			4.45%
Issuance			$ 600.0
Eversource Parent Series H Senior Notes | Senior Notes | Eversource Parent | Eversource
Debt Instrument [Line Items]
Interest Rate										3.15%
Repayments of Debt										$ (300.0)
Eversource Parent Series Q Senior Notes | Senior Notes | Eversource Parent | Eversource
Debt Instrument [Line Items]
Interest Rate					0.80%
Repayments of Debt					$ (300.0)
NSTAR Gas Series Y First Mortgage Bonds | First Mortgage | NSTAR Gas
Debt Instrument [Line Items]
Interest Rate							4.86%
Issuance							$ 205.0
NSTAR Gas Series Z First Mortgage Bonds | First Mortgage | NSTAR Gas
Debt Instrument [Line Items]
Interest Rate							5.30%
Issuance							$ 20.0
NSTAR Gas Series R First Mortgage Bonds | First Mortgage | NSTAR Gas
Debt Instrument [Line Items]
Interest Rate								2.33%
Repayments of Debt								$ (75.0)
Yankee Gas Series Y First Mortgage Bonds | First Mortgage | Yankee Gas Services Company
Debt Instrument [Line Items]
Interest Rate						5.02%
Issuance						$ 148.0
Yankee Gas Series Z First Mortgage Bonds | First Mortgage | Yankee Gas Services Company
Debt Instrument [Line Items]
Interest Rate						5.55%
Issuance						$ 37.0
Yankee Gas Series M First Mortgage Bonds | First Mortgage | Yankee Gas Services Company
Debt Instrument [Line Items]
Interest Rate				3.35%
Repayments of Debt				$ (75.0)
EGMA Series F First Mortgage Bonds | First Mortgage | EGMA Series
Debt Instrument [Line Items]
Interest Rate				4.77%
Issuance				$ 125.0