DEBT - NJR SHORT-TERM DEBT (Details) - NJR	Sep. 30, 2025 USD ($) debtInstrument	Sep. 30, 2024 USD ($)	Aug. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)
Letter of Credit
Short-term Debt [Line Items]
Number of debt instruments (in debt instruments) | debtInstrument	24
Letters of credit outstanding, amount	$ 21,400,000	$ 12,300,000
Revolving Credit Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity, incremental increase			$ 50,000,000
Line of credit facility, maximum borrowing capacity, maximum increase			750,000,000
Line of Credit
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity, maximum increase			75,000,000
Committed Credit Facilities Due August 2029 | Revolving Credit Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 575,000,000	$ 575,000,000	$ 575,000,000	$ 650,000,000