DEBT - NJNG SHORT-TERM DEBT (Details) - NJNG	Sep. 30, 2025 USD ($) debtInstrument	Sep. 30, 2024 USD ($)	Aug. 31, 2024 USD ($)
Letter of Credit
Line of Credit Facility [Line Items]
Number of debt instruments (in debt instruments) | debtInstrument	2
Letters of credit outstanding, amount	$ 700,000	$ 700,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity, incremental increase			$ 50,000,000
Line of credit facility, maximum borrowing capacity, maximum increase			350,000,000
Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity, maximum increase			30,000,000
Committed Credit Facilities Due August 2029 | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000	$ 250,000,000	$ 250,000,000