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Sale Leaseback Transaction, Term Of Lease

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DEBT - LONG TERM DEBT (Details) - USD ($)	9 Months Ended
DEBT - LONG TERM DEBT (Details) - USD ($)	Jun. 30, 2023	Jun. 30, 2022	Oct. 24, 2022
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - natural gas meters	$ 8,441,000	$ 17,300,000
Proceeds from sale leaseback transactions - solar	163,619,000	3,300,000
Clean Energy Ventures
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - solar	$ 163,600,000	3,300,000
Clean Energy Ventures \| Minimum
Debt Instrument [Line Items]
Sale leaseback transaction lease term	5 years
Clean Energy Ventures \| Maximum
Debt Instrument [Line Items]
Sale leaseback transaction lease term	15 years
NJNG
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - natural gas meters	$ 8,400,000	17,300,000
Payments for sale leaseback transaction	$ 0	$ 1,100,000
NJR \| Senior Notes \| Unsecured Senior Notes 6.14%, Maturing in 2032
Debt Instrument [Line Items]
Debt issued			$ 50,000,000
Stated interest rate			6.14%
NJNG \| Senior Notes \| Unsecured Senior Notes 5.47%, Maturing in 2052
Debt Instrument [Line Items]
Debt issued			$ 125,000,000
Stated interest rate			5.47%