SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Increase due to CMA acquisition			$ 24,200
Allowance for uncollectible accounts for late fees and other receivable amounts	$ 486,297	$ 417,406	358,900	$ 224,800
Restatement Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for uncollectible accounts for late fees and other receivable amounts			23,800	23,800
CL&P
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Increase due to CMA acquisition			0
Allowance for uncollectible accounts for late fees and other receivable amounts	225,320	181,319	157,400	97,300
CL&P | Restatement Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for uncollectible accounts for late fees and other receivable amounts			22,200	22,200
NSTAR Electric
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Increase due to CMA acquisition			0
Allowance for uncollectible accounts for late fees and other receivable amounts	94,958	97,005	91,600	75,400
NSTAR Electric | Restatement Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for uncollectible accounts for late fees and other receivable amounts			(1,300)	(1,300)
PSNH
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Increase due to CMA acquisition			0
Allowance for uncollectible accounts for late fees and other receivable amounts	29,236	24,331	17,200	10,500
PSNH | Restatement Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for uncollectible accounts for late fees and other receivable amounts			300	$ 300
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	417,406	358,851	224,821
Additions, Charged to Costs and Expense	61,876	60,886	53,461
Additions, Charged to Other Accounts	112,533	110,572	145,005
Deductions	105,518	112,903	64,436
Balance at end of period	486,297	417,406	358,851
Allowance for Doubtful Accounts | CL&P
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	181,319	157,447	97,348
Additions, Charged to Costs and Expense	15,578	13,495	12,882
Additions, Charged to Other Accounts	59,485	57,779	71,223
Deductions	31,062	47,402	24,006
Balance at end of period	225,320	181,319	157,447
Allowance for Doubtful Accounts | NSTAR Electric
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	97,005	91,583	75,406
Additions, Charged to Costs and Expense	21,550	16,649	15,293
Additions, Charged to Other Accounts	12,412	20,064	23,424
Deductions	36,009	31,291	22,540
Balance at end of period	94,958	97,005	91,583
Allowance for Doubtful Accounts | PSNH
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	24,331	17,157	10,497
Additions, Charged to Costs and Expense	9,211	13,113	5,164
Additions, Charged to Other Accounts	2,539	3,135	7,692
Deductions	6,845	9,074	6,196
Balance at end of period	$ 29,236	$ 24,331	$ 17,157