COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2019	Sep. 30, 2018
Commitments and Contingencies [Line Items]
Number Of Former Manufactured Gas Sites Where We Own Or Retain Legal Responsibility For Environmental Conditions		12
Number of sites where regulatory closure has been achieved					3
AAO associated with MGP costs requested amount, cap		$ 15.0
Number of sites with ongoing groundwater monitoring	8
Environmental Reserve Estimate Range, Low	$ 5.6		$ 4.0
Environmental Reserve Estimate Range, High	7.0		$ 7.0
Environmental Reserve Estimate, Actual	$ 1.6
Percentage yield of high consequence pipeline areas				30.00%