INCOME TAXES - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Current Income Taxes:
Federal	$ 77,500	$ (23,400)	$ 75,800
State	37,500	14,300	600
Total Current	115,000	(9,100)	76,400
Deferred Income Taxes, Net:
Federal	63,700	266,300	(900)
State	(36,400)	169,600	86,300
Total Deferred	27,313	435,889	85,405
Investment Tax Credits, Net	(2,000)	(2,100)	(2,100)
Income Tax Expense	140,286	424,664	159,684
CL&P
Current Income Taxes:
Federal	191,100	25,900	(10,800)
State	70,900	(6,800)	(2,300)
Total Current	262,000	19,100	(13,100)
Deferred Income Taxes, Net:
Federal	(66,500)	107,900	130,300
State	(28,300)	67,500	53,700
Total Deferred	(94,819)	175,424	184,037
Income Tax Expense	167,203	194,459	170,909
NSTAR Electric
Current Income Taxes:
Federal	118,900	65,900	50,700
State	37,200	15,200	7,800
Total Current	156,100	81,100	58,500
Deferred Income Taxes, Net:
Federal	10,000	63,900	50,100
State	25,600	47,300	46,100
Total Deferred	35,596	111,177	96,224
Income Tax Expense	190,030	190,576	152,996
PSNH
Current Income Taxes:
Federal	57,300	(1,700)	(40,000)
State	23,500	(5,200)	(20,000)
Total Current	80,800	(6,900)	(60,000)
Deferred Income Taxes, Net:
Federal	3,700	50,800	81,200
State	7,600	26,300	37,800
Total Deferred	11,291	77,082	118,970
Income Tax Expense	$ 92,146	$ 70,245	$ 59,014