DEBT - NJR SHORT-TERM DEBT (Details) - NJR	12 Months Ended
	Sep. 30, 2021 USD ($) mutualOption	Sep. 30, 2022 USD ($) debtInstrument	Aug. 30, 2022 USD ($)
Letters of Credit on Behalf of NJRES
Short-term Debt [Line Items]
Number of debt instruments (in debt instruments) | debtInstrument		7
Letters of credit outstanding, amount	$ 10,600,000	$ 9,700,000
Revolving Credit Facility
Short-term Debt [Line Items]
Number of mutual options | mutualOption	2
Number of mutual options, extension period	1 year
Line of credit facility, maximum borrowing capacity, incremental increase	$ 50,000,000
Line of credit facility, maximum borrowing capacity, maximum increase	250,000,000
Revolving Credit Facility | Swingline Loan
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	60,000,000		$ 70,000,000
Line of Credit
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	75,000,000
Committed Credit Facilities Due September 2026 | Revolving Credit Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	500,000,000
Committed Credit Facilities Due September 2027 | Revolving Credit Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500,000,000	$ 650,000,000	$ 650,000,000