SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current Assets:
Cash	$ 135,351	$ 26,656
Accounts Receivable from Subsidiaries	1,847,094	1,651,325
Prepayments and Other Current Assets, Including Assets Held for Sale	352,958	315,368
Total Current Assets	5,077,186	5,076,073
Deferred Debits and Other Assets:
Equity Method Investments	166,200	168,700
Goodwill	4,233,767	3,571,333	$ 4,532,100
Long-Term Assets Held for Sale	0	2,611,145
Other Long-Term Assets	997,883	811,521
Total Deferred Debits and Other Assets	12,778,566	13,531,878
Total Assets (as of)	63,786,711	59,594,529
Current Liabilities:
Notes Payable	1,525,445	2,042,793
Long-Term Debt – Current Portion	1,392,948	1,003,150
Accounts Payable to Subsidiaries	1,859,692	1,736,880
Accrued Interest	380,231	341,558
Other Current Liabilities	894,219	853,491
Total Current Liabilities	7,808,512	6,720,957
Liabilities, Noncurrent [Abstract]
Long-Term Liabilities Held for Sale	0	398,859
Other Long-Term Liabilities	1,101,932	773,999
Total Deferred Credits and Other Liabilities	12,472,065	11,652,918
Capitalization:
Long-Term Debt	26,872,433	25,701,627
Common Shareholders' Equity:
Capital Surplus, Paid in	9,937,878	9,428,905
Retained Earnings	4,504,983	3,929,141
Accumulated Other Comprehensive Income/(Loss)	(20,507)	(26,472)
Treasury Stock	(139,356)	(170,809)
Common Shareholders' Equity	16,197,271	15,039,387	$ 14,173,892	$ 15,473,158
Total Liabilities and Capitalization	63,786,711	59,594,529
Eversource
Current Assets:
Cash	200	1,083
Accounts Receivable from Subsidiaries	215,193	100,320
Notes Receivable from Subsidiaries	1,592,100	2,051,400
Prepayments and Other Current Assets, Including Assets Held for Sale	57,002	96,313
Total Current Assets	1,864,495	2,249,116
Deferred Debits and Other Assets:
Equity Method Investments	21,413,181	20,080,215
Notes Receivable from Subsidiaries	2,296,500	2,296,500
Accumulated Deferred Income Taxes	100,941	113,718
Goodwill	3,550,070	3,231,811
Long-Term Assets Held for Sale	0	335,393
Other Long-Term Assets	26,700	24,582
Total Deferred Debits and Other Assets	27,387,392	26,082,219
Total Assets (as of)	29,251,887	28,331,335
Current Liabilities:
Notes Payable	1,280,000	1,538,011
Long-Term Debt – Current Portion	1,002,439	600,000
Accounts Payable to Subsidiaries	43,698	45,326
Accrued Interest	169,516	168,748
Other Current Liabilities	97,176	57,923
Total Current Liabilities	2,592,829	2,410,008
Liabilities, Noncurrent [Abstract]
Long-Term Liabilities Held for Sale	0	15,028
Other Long-Term Liabilities	115,299	137,656
Total Deferred Credits and Other Liabilities	115,299	152,684
Capitalization:
Long-Term Debt	10,346,488	10,729,256
Common Shareholders' Equity:
Common Shares	1,914,273	1,878,622
Capital Surplus, Paid in	9,937,878	9,428,905
Retained Earnings	4,504,983	3,929,141
Accumulated Other Comprehensive Income/(Loss)	(20,507)	(26,472)
Treasury Stock	(139,356)	(170,809)
Common Shareholders' Equity	16,197,271	15,039,387
Total Liabilities and Capitalization	$ 29,251,887	$ 28,331,335