SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - STATEMENT OF CASH FLOW (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Activities:
Net Income	$ 1,412,394	$ 1,228,046	$ 1,212,686
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Equity in Earnings of Subsidiaries	(22,900)	(14,200)	(14,200)
Deferred Income Taxes	346,779	347,056	257,154
Other	(39,192)	(64,640)	(25,957)
Receivables and Unbilled Revenues, Net	(470,593)	(135,505)	(351,843)
Taxes Receivable/Accrued, Net	18,358	(110,621)	43,819
Other Current Assets and Liabilities, Net	(45,583)	3,710	(24,995)
Net Cash Flows Provided by Operating Activities	2,401,293	1,962,600	1,682,572
Investing Activities:
Other Investing Activities	20,420	22,178	23,809
Net Cash Flows Used in Investing Activities	(4,130,490)	(3,447,374)	(4,129,275)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	197,058	0	928,992
Cash Dividends on Common Shares	(860,033)	(805,439)	(744,665)
Issuance of Long-Term Debt	4,045,000	3,230,000	2,760,000
Retirement of Long-Term Debt	(1,175,000)	(1,142,500)	(327,236)
Other Financing Activities	(48,185)	(46,625)	14,273
Net Cash Flows Provided by Financing Activities	2,029,941	1,440,832	2,594,590
Net Increase/(Decrease) in Cash, Cash Equivalents and Restricted Cash	300,744	(43,942)	147,887
Cash, Cash Equivalents and Restricted Cash - Beginning of Year	221,008	264,950	117,063
Cash, Cash Equivalents and Restricted Cash - End of Year	521,752	221,008	264,950
Cash Paid/(Received) During the Year for:
Interest	636,200	568,700	518,000
Income Taxes	77,900	121,600	48,900
Eversource
Operating Activities:
Net Income	1,404,875	1,220,527	1,205,167
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Equity in Earnings of Subsidiaries	(1,565,474)	(1,345,199)	(1,309,630)
Cash Dividends Received from Subsidiaries	855,600	1,037,100	485,800
Deferred Income Taxes	25,823	20,293	(4,667)
Other	26,455	36,910	39,940
Receivables and Unbilled Revenues, Net	(9,935)	(3,758)	(14,575)
Taxes Receivable/Accrued, Net	(21,627)	(19,455)	35,300
Accounts Payable to Subsidiaries	(4,079)	19,185	14,091
Other Current Assets and Liabilities, Net	35,090	8,144	21,284
Net Cash Flows Provided by Operating Activities	746,728	973,747	472,710
Investing Activities:
Capital Contributions to Subsidiaries	(1,499,300)	(1,033,000)	(1,899,340)
Return of Capital from Subsidiaries	12,000	178,800	80,000
Increase in Notes Receivable from Subsidiaries	(724,400)	(140,200)	(264,300)
Other Investing Activities	(1,289)	(3,196)	(367)
Net Cash Flows Used in Investing Activities	(2,212,989)	(997,596)	(2,084,007)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	197,058	0	928,992
Cash Dividends on Common Shares	(860,033)	(805,439)	(744,665)
Issuance of Long-Term Debt	2,800,000	1,000,000	1,550,000
Retirement of Long-Term Debt	(750,000)	(450,000)	0
Increase (Decrease) in Notes Payable to Eversource Parent	99,250	288,625	(170,545)
Other Financing Activities	(19,193)	(9,545)	46,480
Net Cash Flows Provided by Financing Activities	1,467,082	23,641	1,610,262
Net Increase/(Decrease) in Cash, Cash Equivalents and Restricted Cash	821	(208)	(1,035)
Cash, Cash Equivalents and Restricted Cash - Beginning of Year	226	434	1,469
Cash, Cash Equivalents and Restricted Cash - End of Year	1,047	226	434
Cash Paid/(Received) During the Year for:
Interest	215,053	164,568	140,694
Income Taxes	$ (20,992)	$ (51,277)	$ (43,158)