DERIVATIVE INSTRUMENTS - VOLUME (Details) - Bcf	9 Months Ended	12 Months Ended
Jun. 30, 2026	Sep. 30, 2025
NJNG \| Long \| Futures
Derivative [Line Items]
Notional amount	27.1	36.1
NJNG \| Long \| Physical Commodity
Derivative [Line Items]
Notional amount	4.7	6.0
ES \| Long \| Physical Commodity
Derivative [Line Items]
Notional amount		5.5
ES \| Short \| Futures
Derivative [Line Items]
Notional amount	(9.8)	(4.7)
ES \| Short \| Physical Commodity
Derivative [Line Items]
Notional amount	(3.3)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-5A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A

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