NATURE OF THE BUSINESS (Details) shares in Thousands	9 Months Ended
	Jun. 30, 2017 subsidiary customer shares
Common Units
Nature of Business [Line Items]
Ownership interest exchanged (in shares) | shares	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%
NJNG
Nature of Business [Line Items]
Total retail customers | customer	528,600
NJR Retail Holdings Corporation
Nature of Business [Line Items]
Number of principal subsidiaries | subsidiary	2