REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenues from alternative revenue programs	$ 1.0	$ (3.1)	$ 2.1	$ 44.6
SJG
Disaggregation of Revenue [Line Items]
Total revenues from alternative revenue programs	$ 0.6	$ (0.2)	$ (0.1)	$ 37.0