SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF (LOSS)/INCOME (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, Captions [Line Items]
Operating Revenues	$ 11,910,705	$ 12,289,336	$ 9,863,085
Operating Expenses:
Other	1,895,703	1,865,328	1,739,685
Operating Income (Loss)	2,399,335	2,198,154	1,993,321
Interest Expense	855,441	678,274	582,334
Other Income, Net:
Equity in (Losses)/Earnings of Subsidiaries	15,500	22,900	14,200
Other (Loss)/Income, Net	348,069	346,088	161,282
(Loss)/Income Before Income Tax Benefit	(275,037)	1,865,968	1,572,269
Income Tax Benefit	159,684	453,574	344,223
Net (Loss)/Income	$ (434,700)	$ 1,412,400	$ 1,228,000
Basic (Loss)/Earnings Per Common Share (in dollars per share)	$ (1.27)	$ 4.05	$ 3.55
Diluted (Loss)/Earnings Per Common Share (in dollars per share)	$ (1.26)	$ 4.05	$ 3.54
Weighted Average Common Shares Outstanding:
Basic (in shares)	349,580,638	346,783,444	343,972,926
Diluted (in shares)	349,840,481	347,246,768	344,631,056
Eversource
Condensed Income Statements, Captions [Line Items]
Operating Revenues	$ 840	$ 0	$ 0
Operating Expenses:
Other	12,769	26,708	43,048
Operating Income (Loss)	(11,929)	(26,708)	(43,048)
Interest Expense	397,281	237,773	163,613
Other Income, Net:
Equity in (Losses)/Earnings of Subsidiaries	(312,040)	1,565,474	1,345,199
Other, Net	188,003	79,383	47,802
Other (Loss)/Income, Net	(124,037)	1,644,857	1,393,001
(Loss)/Income Before Income Tax Benefit	(533,247)	1,380,376	1,186,340
Income Tax Benefit	(91,007)	(24,499)	(34,187)
Net (Loss)/Income	$ (442,240)	$ 1,404,875	$ 1,220,527
Basic (Loss)/Earnings Per Common Share (in dollars per share)	$ (1.27)	$ 4.05	$ 3.55
Diluted (Loss)/Earnings Per Common Share (in dollars per share)	$ (1.26)	$ 4.05	$ 3.54
Weighted Average Common Shares Outstanding:
Basic (in shares)	349,580,638	346,783,444	343,972,926
Diluted (in shares)	349,840,481	347,246,768	344,631,056