SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF COMPREHENSIVE (LOSS)/INCOME (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Statement of Income Captions [Line Items]
Net (Loss)/Income	$ (434,700)	$ 1,412,400	$ 1,228,000
Other Comprehensive Income/(Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	20	20	972
Changes in Unrealized Gains/(Losses) on Marketable Securities	1,252	(1,636)	(671)
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	4,412	4,470	33,835
Other Comprehensive Income, Net of Tax	5,684	2,854	34,136
Comprehensive (Loss)/Income	(436,556)	1,407,729	1,254,663
Eversource
Condensed Statement of Income Captions [Line Items]
Net (Loss)/Income	(442,240)	1,404,875	1,220,527
Other Comprehensive Income/(Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	20	20	972
Changes in Unrealized Gains/(Losses) on Marketable Securities	1,252	(1,636)	(671)
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	4,412	4,470	33,835
Other Comprehensive Income, Net of Tax	5,684	2,854	34,136
Comprehensive (Loss)/Income	$ (436,556)	$ 1,407,729	$ 1,254,663