NATURE OF THE BUSINESS (Details)	12 Months Ended
Sep. 30, 2019 subsidiary customer
NJNG
Investment [Line Items]
Total retail customers (in customers) \| customer	547,600
NJR Retail Holdings Corporation
Investment [Line Items]
Number of principal subsidiaries (in subsidiaries) \| subsidiary	2
Steckman Ridge
Investment [Line Items]
Ownership interest, percent	50.00%
PennEast
Investment [Line Items]
Ownership interest, percent	20.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant