ASSET RETIREMENT OBLIGATIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Estimated Accretion
2018	$ 1,669
2019	1,745
2020	1,823
2021	1,908
2022	1,994
Total	9,139
NJNG
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at period beginning	25,640	$ 24,825
Accretion	1,427	1,366
Additions	135	1,880
Revisions in estimated cash flows	0	(2,133)
Retirements	(258)	(298)
Reclassification to held for sale or sold	0	0
Balance at period end	26,944	25,640
Clean Energy Ventures
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at period beginning	3,048	6,595
Accretion	150	198
Additions	904	517
Revisions in estimated cash flows	0	0
Retirements	0	0
Reclassification to held for sale or sold	0	(4,262)
Balance at period end	$ 4,102	$ 3,048