FAIR VALUE - DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance leases	$ 31,352	$ 30,300
NJNG
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance leases	31,352
Debt issuance costs	9,770	9,528
NJR
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs	3,700	3,800
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance leases	20,900	15,700
Level 2 \| NJNG \| Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	1,467,845	1,292,845
Level 2 \| NJNG \| Fair market value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	1,097,088	979,388
Level 2 \| NJR \| Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	1,120,000	1,070,000
Level 2 \| NJR \| Fair market value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 1,009,448	$ 966,968

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482925/835-30-45-3

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+ References

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147478964/842-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479041/842-20-45-1

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+ References

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