INCOME TAXES - Schedule of Unrecognized Tax Benefits Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Unrecognized Tax Benefits [Roll Forward]
Beginning Balance	$ 93.7	$ 81.3	$ 67.1
Gross Increases - Current Year	11.9	14.2	23.4
Gross Increases - Prior Year	5.9	11.0	0.1
Gross Decreases - Prior Year		(0.2)	(0.1)
Lapse of Statute of Limitations	(13.3)	(12.6)	(9.2)
Ending Balance	98.2	93.7	81.3
CL&P
Unrecognized Tax Benefits [Roll Forward]
Beginning Balance	21.9	25.8	25.5
Gross Increases - Current Year	3.2	2.9	4.0
Gross Increases - Prior Year	1.1	0.0	0.1
Gross Decreases - Prior Year		(0.2)	0.0
Lapse of Statute of Limitations	(4.6)	(6.6)	(3.8)
Ending Balance	$ 21.6	$ 21.9	$ 25.8