NATURE OF THE BUSINESS (Details) shares in Thousands	6 Months Ended
	Mar. 31, 2018 subsidiary customer shares	Sep. 30, 2015 shares
Common Units
Nature of Business [Line Items]
Ownership interest exchanged (in shares) | shares	1,840	1,840
Steckman Ridge
Nature of Business [Line Items]
Equity method investment, ownership percentage	50.00%
PennEast
Nature of Business [Line Items]
Equity method investment, ownership percentage	20.00%
Natural Gas Distribution
Nature of Business [Line Items]
Total retail customers | customer	536,900
NJR Retail Holdings Corporation
Nature of Business [Line Items]
Number of principal subsidiaries | subsidiary	2