INCOME TAXES - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current Income Taxes:
Federal	$ 95,800	$ 21,500	$ 73,600
State	13,600	(21,600)	19,100
Total Current	109,400	(100)	92,700
Deferred Income Taxes, Net:
Federal	198,800	199,700	173,500
State	148,000	147,400	83,700
Total Deferred	346,779	347,056	257,154
Investment Tax Credits, Net	(2,600)	(2,800)	(3,700)
Income Tax Expense	453,574	344,223	346,186
CL&P
Current Income Taxes:
Federal	106,200	15,000	12,000
State	20,100	(7,000)	(6,100)
Total Current	126,300	8,000	5,900
Deferred Income Taxes, Net:
Federal	17,200	76,300	101,100
State	28,200	47,600	43,400
Total Deferred	45,381	123,889	144,527
Investment Tax Credits, Net	(500)	(600)	(700)
Income Tax Expense	171,198	131,273	149,702
NSTAR Electric
Current Income Taxes:
Federal	55,000	52,300	53,900
State	8,700	6,200	6,900
Total Current	63,700	58,500	60,800
Deferred Income Taxes, Net:
Federal	35,600	16,300	33,800
State	42,400	41,200	38,800
Total Deferred	78,039	57,507	72,595
Investment Tax Credits, Net	(1,700)	(1,700)	(2,600)
Income Tax Expense	139,977	114,335	130,828
PSNH
Current Income Taxes:
Federal	29,600	43,100	20,600
State	5,900	10,800	3,800
Total Current	35,500	53,900	24,400
Deferred Income Taxes, Net:
Federal	5,900	(14,900)	(1,300)
State	9,900	400	8,600
Total Deferred	15,765	(14,530)	7,337
Investment Tax Credits, Net	0	0	0
Income Tax Expense	$ 51,314	$ 39,433	$ 31,680