FAIR VALUE - DEBT (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance leases	$ 31,900	$ 20,100
NJR
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs	3,700	3,300
NJNG
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs	10,500	9,100
Level 2 \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	2,412,845	2,102,845
Level 2 \| Fair market value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 2,154,528	$ 2,288,544

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

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