INCOME TAXES - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Contingency [Line Items]
Federal Income Taxes	$ (48.8)
State Income Taxes	0.4
Total Cash Paid/(Received) for Income Taxes, Net of Refunds	(48.4)	$ (69.6)	$ 39.2
CL&P
Income Tax Contingency [Line Items]
Federal Income Taxes	113.1
State Income Taxes	22.6
Total Cash Paid/(Received) for Income Taxes, Net of Refunds	135.7	(47.4)	(44.1)
NSTAR Electric
Income Tax Contingency [Line Items]
Federal Income Taxes	124.5
State Income Taxes	40.3
Total Cash Paid/(Received) for Income Taxes, Net of Refunds	164.8	118.7	31.3
PSNH
Income Tax Contingency [Line Items]
Federal Income Taxes	60.0
State Income Taxes	23.0
Total Cash Paid/(Received) for Income Taxes, Net of Refunds	83.0	$ (36.0)	$ (59.9)
Connecticut
Income Tax Contingency [Line Items]
State Income Taxes	6.2
Connecticut | CL&P
Income Tax Contingency [Line Items]
State Income Taxes	22.4
Connecticut | NSTAR Electric
Income Tax Contingency [Line Items]
State Income Taxes	0.0
Connecticut | PSNH
Income Tax Contingency [Line Items]
State Income Taxes	0.0
Massachusetts
Income Tax Contingency [Line Items]
State Income Taxes	(8.7)
Massachusetts | NSTAR Electric
Income Tax Contingency [Line Items]
State Income Taxes	40.3
New Hampshire | CL&P
Income Tax Contingency [Line Items]
State Income Taxes	0.0
New Hampshire | NSTAR Electric
Income Tax Contingency [Line Items]
State Income Taxes	0.0
New Hampshire | PSNH
Income Tax Contingency [Line Items]
State Income Taxes	22.9
Other
Income Tax Contingency [Line Items]
State Income Taxes	2.9
Other | CL&P
Income Tax Contingency [Line Items]
State Income Taxes	0.2
Other | NSTAR Electric
Income Tax Contingency [Line Items]
State Income Taxes	0.0
Other | PSNH
Income Tax Contingency [Line Items]
State Income Taxes	$ 0.1