DEBT - SCHEDULE OF LONG-TERM DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Meter financing obligation	$ 10,366	$ 16,026
Total long-term debt	3,250,387	2,879,464
NJNG
Debt Instrument [Line Items]
Less: Debt issuance costs	(11,296)	(10,899)
Less: Current maturities of long-term debt	(8,228)	(58,649)
Total long-term debt	1,811,798	1,609,871
NJR
Debt Instrument [Line Items]
Less: Debt issuance costs	(2,916)	(3,011)
Less: Current maturities of long-term debt	(100,000)	(100,000)
Total long-term debt	1,017,084	1,016,989
CEV
Debt Instrument [Line Items]
Long-term debt	471,469	282,962
Less: Current maturities of long-term debt	(49,964)	(30,358)
Total CEV long-term debt	421,505	252,604
Meter financing obligation | NJNG
Debt Instrument [Line Items]
Meter financing obligation	$ 33,477	31,574
First Mortgage Bonds | Series OO | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.00%
Long-term debt	$ 46,500	46,500
First Mortgage Bonds | Series PP | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.15%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series RR | NJNG
Debt Instrument [Line Items]
Stated interest rate	4.61%
Long-term debt	$ 55,000	55,000
First Mortgage Bonds | Series SS | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.82%
Long-term debt	$ 0	50,000
First Mortgage Bonds | Series TT | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.66%
Long-term debt	$ 100,000	100,000
First Mortgage Bonds | Series UU | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.63%
Long-term debt	$ 125,000	125,000
First Mortgage Bonds | Series VV | NJNG
Debt Instrument [Line Items]
Stated interest rate	4.01%
Long-term debt	$ 125,000	125,000
First Mortgage Bonds | Series WW | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.50%
Long-term debt	$ 10,300	10,300
First Mortgage Bonds | Series XX | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.38%
Long-term debt	$ 10,500	10,500
First Mortgage Bonds | Series YY | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.45%
Long-term debt	$ 15,000	15,000
First Mortgage Bonds | Series ZZ | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.76%
Long-term debt	$ 100,000	100,000
First Mortgage Bonds | Series AAA | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.86%
Long-term debt	$ 85,000	85,000
First Mortgage Bonds | Series BBB | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.75%
Long-term debt	$ 9,545	9,545
First Mortgage Bonds | Series CCC | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.00%
Long-term debt	$ 41,000	41,000
First Mortgage Bonds | Series DDD | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series EEE | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series FFF | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.33%
Long-term debt	$ 25,000	25,000
First Mortgage Bonds | Series GGG | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.87%
Long-term debt	$ 25,000	25,000
First Mortgage Bonds | Series HHH | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.97%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series III | NJNG
Debt Instrument [Line Items]
Stated interest rate	2.97%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series JJJ | NJNG
Debt Instrument [Line Items]
Stated interest rate	3.07%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series LLL | NJNG
Debt Instrument [Line Items]
Stated interest rate	4.37%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series MMM | NJNG
Debt Instrument [Line Items]
Stated interest rate	4.71%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series NNN | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.47%
Long-term debt	$ 125,000	125,000
First Mortgage Bonds | Series OOO | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.56%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series PPP | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.85%
Long-term debt	$ 50,000	50,000
First Mortgage Bonds | Series QQQ | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.82%
Long-term debt	$ 125,000	125,000
First Mortgage Bonds | Series RRR | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.49%
Long-term debt	$ 75,000	75,000
First Mortgage Bonds | Series SSS | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.16%
Long-term debt	$ 100,000	0
First Mortgage Bonds | Series TTT | NJNG
Debt Instrument [Line Items]
Stated interest rate	5.85%
Long-term debt	$ 100,000	0
Unsecured senior notes 3.48% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.48%
Long-term debt	$ 0	100,000
Unsecured senior notes 3.54% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.54%
Long-term debt	$ 100,000	100,000
Unsecured senior notes 3.96% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.96%
Long-term debt	$ 100,000	100,000
Unsecured senior notes 3.29% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.29%
Long-term debt	$ 150,000	150,000
Unsecured senior note 3.50% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.50%
Long-term debt	$ 130,000	130,000
Unsecured senior note 3.60% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.60%
Long-term debt	$ 130,000	130,000
Unsecured senior note 3.13% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 120,000	120,000
Unsecured senior notes 3.25% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.25%
Long-term debt	$ 80,000	80,000
Unsecured Senior Notes 4.38% | NJR
Debt Instrument [Line Items]
Stated interest rate	4.38%
Long-term debt	$ 110,000	110,000
Unsecured Senior Notes 3.64% | NJR
Debt Instrument [Line Items]
Stated interest rate	3.64%
Long-term debt	$ 50,000	50,000
Unsecured Senior Notes 6.14% | NJR
Debt Instrument [Line Items]
Stated interest rate	6.14%
Long-term debt	$ 50,000	50,000
Unsecured Senior Notes 5.55% | NJR
Debt Instrument [Line Items]
Stated interest rate	5.55%
Long-term debt	$ 100,000	$ 0