DEBT - NJR AND NJNG LONG-TERM DEBT (Details) - USD ($) $ in Millions	Nov. 07, 2024	Sep. 30, 2024	Jun. 26, 2024	Sep. 28, 2023
NJNG
Debt Instrument [Line Items]
NJBPU dividend restriction, equity to capitalization ratio		53.40%
Minimum | NJNG
Debt Instrument [Line Items]
NJBPU dividend restriction, equity to capitalization ratio		30.00%
First Mortgage Bonds | NJNG
Debt Instrument [Line Items]
Maximum amount that can be issued		$ 1,400.0
Senior Notes | NJNG
Debt Instrument [Line Items]
Face amount			$ 200.0	$ 100.0
Senior Notes | Unsecured Senior Notes 5.56% | NJNG
Debt Instrument [Line Items]
Face amount				$ 50.0
Stated interest rate				5.56%
Senior Notes | Unsecured Senior Notes 5.58% | NJNG
Debt Instrument [Line Items]
Face amount				$ 50.0
Stated interest rate				5.85%
Senior Notes | Unsecured Senior Notes 5.82% | NJNG
Debt Instrument [Line Items]
Face amount			$ 125.0
Stated interest rate			5.82%
Senior Notes | Unsecured Senior Notes 5.49% | NJNG
Debt Instrument [Line Items]
Face amount			$ 75.0
Stated interest rate			5.49%
Senior Notes | Subsequent Event | Unsecured Senior Notes 5.55% | NJR
Debt Instrument [Line Items]
Face amount	$ 100.0
Stated interest rate	5.55%