NATURE OF THE BUSINESS (Details)		9 Months Ended
	Jun. 01, 2018 MW	Jun. 30, 2018 subsidiary customer
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		537,700
NJR Retail Holdings Corporation
Nature of Business [Line Items]
Number of principal subsidiaries | subsidiary		2
Clean Energy Ventures
Nature of Business [Line Items]
Wind farm total capacity | MW	9.7