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Sale Leaseback Transaction, Net Proceeds, Financing Activities, Solar

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DEBT - LONG TERM DEBT (Details) - USD ($)	9 Months Ended
DEBT - LONG TERM DEBT (Details) - USD ($)	Jun. 30, 2024	Jun. 30, 2023	Jun. 26, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - natural gas meters	$ 8,814,000	$ 8,441,000
Proceeds from sale leaseback transactions - solar	24,394,000	163,619,000
CEV
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - solar	24,400,000	163,600,000
NJNG
Debt Instrument [Line Items]
Proceeds from sale leaseback transactions - natural gas meters	$ 8,800,000	$ 8,400,000
NJNG \| Senior Notes
Debt Instrument [Line Items]
Face amount			$ 200,000,000	$ 100,000,000
NJNG \| Senior Notes \| Unsecured Senior Notes 5.56%
Debt Instrument [Line Items]
Face amount				$ 50,000,000
Stated interest rate				5.56%
NJNG \| Senior Notes \| Unsecured Senior Notes 5.85%
Debt Instrument [Line Items]
Face amount				$ 50,000,000
Stated interest rate				5.85%
NJNG \| Senior Notes \| Unsecured Senior Notes 5.82%
Debt Instrument [Line Items]
Face amount			$ 125,000,000
Stated interest rate			5.82%
NJNG \| Senior Notes \| Unsecured Senior Notes 5.49%
Debt Instrument [Line Items]
Face amount			$ 75,000,000
Stated interest rate			5.49%