SCHEDULE I - FINANCIAL INFORMATION OF REGISTRANT - BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current Assets:
Cash	$ 53,873	$ 47,597
Accounts Receivable from Subsidiaries	1,431,531	1,517,138
Prepayments and Other Current Assets	355,762	382,603
Total Current Assets	4,247,994	4,223,198
Deferred Debits and Other Assets:
Carrying Value as of December 31, 2023	660,473	2,176,080
Goodwill	4,532,100	4,522,632	$ 4,477,300
Other Long-Term Assets	592,080	541,344
Total Deferred Debits and Other Assets	11,865,644	12,894,882
Total Assets (as of)	55,612,245	53,230,900
Current Liabilities:
Notes Payable	1,930,422	1,442,200
Long-Term Debt – Current Portion	824,847	1,320,129
Accounts Payable to Subsidiaries	1,869,187	2,113,905
Other Current Liabilities	1,081,981	989,053
Total Current Liabilities	6,341,397	6,799,283
Liabilities, Noncurrent [Abstract]
Other Long-Term Liabilities	961,239	888,081
Total Deferred Credits and Other Liabilities	10,985,489	10,668,403
Capitalization:
Long-Term Debt	23,588,616	19,723,994
Common Shareholders' Equity:
Capital Surplus, Paid in	8,460,876	8,401,731
Retained Earnings	4,142,515	5,527,153
Accumulated Other Comprehensive Loss	(33,737)	(39,421)
Treasury Stock	(195,682)	(216,225)
Common Shareholders' Equity	14,173,892	15,473,158	$ 14,599,844	$ 14,063,566
Total Liabilities and Capitalization	55,612,245	53,230,900
Eversource
Current Assets:
Cash	542	971
Accounts Receivable from Subsidiaries	60,191	53,338
Notes Receivable from Subsidiaries	2,045,570	1,074,800
Prepayments and Other Current Assets	103,735	23,597
Total Current Assets	2,210,038	1,152,706
Deferred Debits and Other Assets:
Carrying Value as of December 31, 2023	17,977,812	18,379,840
Notes Receivable from Subsidiaries	2,296,500	1,896,500
Accumulated Deferred Income Taxes	10,131	0
Goodwill	3,852,524	3,852,524
Other Long-Term Assets	28,287	108,867
Total Deferred Debits and Other Assets	24,165,254	24,237,731
Total Assets (as of)	26,375,292	25,390,437
Current Liabilities:
Notes Payable	1,564,575	1,442,200
Long-Term Debt – Current Portion	364,653	1,207,047
Accounts Payable to Subsidiaries	38,051	33,530
Accrued Interest	106,070	72,951
Other Current Liabilities	41,268	39,856
Total Current Liabilities	2,114,617	2,795,584
Liabilities, Noncurrent [Abstract]
Accumulated Deferred Income Taxes	0	8,498
Other Long-Term Liabilities	134,432	140,393
Total Deferred Credits and Other Liabilities	134,432	148,891
Capitalization:
Long-Term Debt	9,952,351	6,972,804
Common Shareholders' Equity:
Common Shares	1,799,920	1,799,920
Capital Surplus, Paid in	8,460,876	8,401,731
Retained Earnings	4,142,515	5,527,153
Accumulated Other Comprehensive Loss	(33,737)	(39,421)
Treasury Stock	(195,682)	(216,225)
Common Shareholders' Equity	14,173,892	15,473,158
Total Liabilities and Capitalization	$ 26,375,292	$ 25,390,437