SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Adjustments to Reconcile Net Income/(Loss) to Net Cash Flows Provided by Operating Activities:
Equity in (Earnings)/Losses of Subsidiaries	$ (19,900)	$ (51,900)	$ (15,500)
Deferred Income Taxes	27,313	435,889	85,405
Loss on Pending Sale of Aquarion	0	297,000	0
Other	(4,826)	(108,365)	(59,886)
Receivables and Unbilled Revenues, Net	(364,156)	(432,620)	(124,393)
Taxes Receivable/Accrued, Net	143,331	55,502	36,357
Other Current Assets and Liabilities, Net	81,671	19,529	(66,202)
Net Cash Flows Provided by Operating Activities	4,113,572	2,159,737	1,646,161
Investing Activities:
Other Investing Activities	30,820	(13,365)	(2,897)
Net Cash Flows Used in Investing Activities	(4,306,163)	(4,535,664)	(4,870,732)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	465,389	989,447	0
Cash Dividends on Common Shares	(1,093,074)	(1,001,488)	(918,995)
Issuance of Long-Term Debt	2,942,353	4,501,623	5,198,345
Retirement of Long-Term Debt	(1,400,331)	(1,949,995)	(2,008,470)
Other Financing Activities	(34,732)	(57,082)	(46,466)
Net Cash Flows Provided by Financing Activities	311,528	2,336,817	2,869,237
Net Increase/(Decrease) in Cash and Restricted Cash	118,937	(39,110)	(355,334)
Cash and Restricted Cash - Beginning of Year	127,308	166,418	521,752
Cash and Restricted Cash - End of Year	246,245	127,308	166,418
Cash Paid/(Received) During the Year for:
Interest	1,182,600	1,014,400	783,200
Income Taxes	(48,400)	(69,600)	39,200
Eversource
Operating Activities:
Net Income/(Loss)	1,692,372	811,653	(442,240)
Adjustments to Reconcile Net Income/(Loss) to Net Cash Flows Provided by Operating Activities:
Equity in (Earnings)/Losses of Subsidiaries	(1,923,453)	(1,359,297)	312,040
Cash Dividends Received from Subsidiaries	1,340,500	1,273,700	1,027,400
Deferred Income Taxes	12,098	(99,692)	(22,256)
Loss on Pending Sale of Aquarion	0	297,000	0
Other	88,966	57,469	(12,834)
Receivables and Unbilled Revenues, Net	(32,527)	(40,129)	(6,853)
Accounts Receivable from EGMA for Acquisition and Integration Costs Allowed for Recovery	(82,346)	0	0
Taxes Receivable/Accrued, Net	86,083	22,464	(80,968)
Accounts Payable to Subsidiaries	(1,628)	7,275	4,521
Other Current Assets and Liabilities, Net	(4,322)	58,572	35,357
Net Cash Flows Provided by Operating Activities	1,175,743	1,029,015	814,167
Investing Activities:
Capital Contributions to Subsidiaries	(755,000)	(2,026,500)	(1,369,700)
Return of Capital from Subsidiaries	11,000	17,000	438,000
Increase/(Decrease) in Notes Receivable from Subsidiaries	459,300	201,500	(1,578,100)
Other Investing Activities	0	0	147,567
Net Cash Flows Used in Investing Activities	(284,700)	(1,808,000)	(2,362,233)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	465,389	989,447	0
Cash Dividends on Common Shares	(1,093,074)	(1,001,488)	(918,995)
Issuance of Long-Term Debt	600,000	2,400,000	3,350,000
Retirement of Long-Term Debt	(600,000)	(1,350,000)	(1,200,000)
(Decrease)/Increase in Notes Payable	(258,011)	(233,894)	329,705
Other Financing Activities	(6,241)	(24,539)	(13,076)
Net Cash Flows Provided by Financing Activities	(891,937)	779,526	1,547,634
Net Increase/(Decrease) in Cash and Restricted Cash	(894)	541	(432)
Cash and Restricted Cash - Beginning of Year	1,156	615	1,047
Cash and Restricted Cash - End of Year	262	1,156	615
Cash Paid/(Received) During the Year for:
Interest	541,910	483,101	366,645
Income Taxes	$ (171,114)	$ 443	$ 23,984