SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF COMPREHENSIVE INCOME(LOSS) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Other Comprehensive Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	$ 20	$ 20	$ 20
Changes in Unrealized Gains on Marketable Securities	0	0	1,252
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	5,945	7,245	4,412
Other Comprehensive Income, Net of Tax	5,965	7,265	5,684
Comprehensive Income/(Loss)	1,698,337	818,918	(436,556)
Eversource
Condensed Statement of Income Captions [Line Items]
Net Income/(Loss)	1,692,372	811,653	(442,240)
Other Comprehensive Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	20	20	20
Changes in Unrealized Gains on Marketable Securities	0	0	1,252
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	5,945	7,245	4,412
Other Comprehensive Income, Net of Tax	5,965	7,265	5,684
Comprehensive Income/(Loss)	$ 1,698,337	$ 818,918	$ (436,556)