EMPLOYEE BENEFITS - Schedule of Compensation Expense and Income Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	$ 33.6	$ 30.0	$ 27.8
Future Income Tax Benefit	8.8	7.8	7.3
CL&P
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	10.5	9.3	8.7
Future Income Tax Benefit	2.7	2.4	2.3
NSTAR Electric
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	11.6	9.6	8.7
Future Income Tax Benefit	3.0	2.5	2.3
PSNH
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	4.3	3.6	3.0
Future Income Tax Benefit	$ 1.1	$ 0.9	$ 0.8