INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Loss Carryforwards [Line Items]
Interest expense on uncertain tax positions	$ 300,000	$ 0	$ 0
Accrued interest payable	400,000	100,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Valuation allowance for tax credit and operating loss carryforward	104,100,000	82,800,000
State and Local Jurisdiction | CL&P
Operating Loss Carryforwards [Line Items]
Change in valuation allowance	17,300,000	18,800,000
Eversource | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Change in valuation allowance	$ 21,300,000	$ 21,300,000