COMMITMENTS AND CONTINGENCIES - CL&P Tropical Storm Isaias Response Investigation (Details) $ in Millions	Jul. 14, 2021 USD ($)	May 07, 2021	Apr. 28, 2021
Loss Contingencies [Line Items]
Loss contingency, allowed rate of ROE, downward adjustment			0.0090
Loss contingency, allowed rate of ROE (in percent)			9.25%
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Non-compliance fine	$ 28.6
Loss contingency, accident reporting violation fines	$ 0.2
Loss contingency, penalty rate as a percent of distribution revenues		2.50%