INVESTMENTS IN EQUITY INVESTEES (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2021 USD ($) mi	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 114,529	$ 208,375
Deferred tax gross up		4,600
Impairment of equity method investment	92,000	0	$ 0
Other than temporary impairment, net of tax	74,500
Steckman Ridge
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	109,050	112,378
Outstanding principal balance	$ 70,400	70,400
Ownership interest, percent	50.00%
PennEast
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 5,479	$ 95,997
Ownership interest, percent	20.00%
Construction plan, pipeline distance (in miles) | mi	120
NJR Pipeline | PennEast
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	20.00%