SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Operating Expenses Cost of Natural Gas Included (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accounting Policies [Abstract]
Eversource - Cost of Natural Gas	$ 857.0	$ 689.6	$ 792.2