SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Statement of Income Captions [Line Items]
Net Income	$ 1,228,046	$ 1,212,686	$ 916,572
Other Comprehensive Income/(Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	972	1,596	1,393
Changes in Unrealized (Losses)/Gains on Marketable Securities	(671)	342	1,166
Change in Funded Status of Pension, SERP and PBOP Benefit Plans	33,835	(13,290)	(7,618)
Other Comprehensive Income/(Loss), Net of Tax	34,136	(11,352)	(5,059)
Comprehensive Income	1,254,663	1,193,815	903,994
Eversource
Condensed Statement of Income Captions [Line Items]
Net Income	1,220,527	1,205,167	909,053
Other Comprehensive Income/(Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	972	1,596	1,393
Changes in Unrealized (Losses)/Gains on Marketable Securities	(671)	342	1,166
Change in Funded Status of Pension, SERP and PBOP Benefit Plans	33,835	(13,290)	(7,618)
Other Comprehensive Income/(Loss), Net of Tax	34,136	(11,352)	(5,059)
Comprehensive Income	$ 1,254,663	$ 1,193,815	$ 903,994