COMMITMENTS AND CONTINGENCIES - CL&P Comprehensive Settlement Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Oct. 01, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 31, 2022	Oct. 27, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Bill of forgiveness		$ 166,418	$ 521,752	$ 221,008			$ 264,950
Regulatory Liabilities		591,750	890,786
Loss related to litigation settlement		0	(72,041)	81,274
Basis points reduction to return on equity, scenario one	0.90%
Basis points reduction to return on equity, scenario two	0.45%
CL&P
Loss Contingencies [Line Items]
Bill of forgiveness		12,243	20,327	74,788			$ 99,809
Regulatory Liabilities		102,239	336,048
Loss related to litigation settlement		$ 0	(72,041)	81,274
CL&P | Customer Assistance Fund
Loss Contingencies [Line Items]
Bill of forgiveness					$ 10,000
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Loss related to litigation settlement				103,600
Customer credits and assistance	$ 75,000
Loss related to litigation settlement, net of tax				$ 86,100
Loss contingency, after-tax earnings impact per share (in dollars per share)				$ 0.25
Unfavorable Regulatory Action | Sales
Loss Contingencies [Line Items]
Loss related to litigation settlement				$ 65,000
Unfavorable Regulatory Action | Oil and Gas, Operation and Maintenance
Loss Contingencies [Line Items]
Loss related to litigation settlement				10,000
Unfavorable Regulatory Action | CL&P
Loss Contingencies [Line Items]
Customer credits						$ 65,000
Customer assistance initiatives						$ 10,000
Regulatory Liabilities				75,000
Unfavorable Regulatory Action | CL&P | Sales
Loss Contingencies [Line Items]
Loss related to litigation settlement				$ 65,000
Unfavorable Regulatory Action | CL&P | Oil and Gas, Operation and Maintenance
Loss Contingencies [Line Items]
Loss related to litigation settlement			$ 10,000