REVENUES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
Other revenues	$ 13,547,244	$ 11,900,809	$ 11,910,705
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Income, Net	Other Income, Net	Other Income, Net
Lease revenue	$ 3,100	$ 2,500	$ 4,600
CL&P
Loss Contingencies [Line Items]
Other revenues	5,240,994	4,614,977	4,578,804
Lease revenue	500	500	700
NSTAR Electric
Loss Contingencies [Line Items]
Other revenues	3,986,599	3,720,877	3,515,539
Lease revenue	$ 1,800	$ 1,200	$ 2,500