REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues from alternative revenue programs	$ 1.0	$ 47.7
SJG
Disaggregation of Revenue [Line Items]
Total revenues from alternative revenue programs	$ (0.8)	$ 37.1