COMMITMENTS AND CONTINGENCIES - CL&P Tropical Storm Isaias Response Investigation (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 14, 2021	May 07, 2021	May 06, 2021	Apr. 28, 2021
Loss Contingencies [Line Items]
Loss contingency, allowed rate of ROE				9.25%
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 30.0
Loss contingency, estimate of possible earnings impact, non-compliance with performance standards			28.4
Loss contingency, estimate of possible earnings impact, accident reporting violation fines			$ 1.6
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%
Loss contingency, after-tax earnings impact per share (in dollars per share)	$ 0.07