DEBT - SCHEDULE OF LONG-TERM DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 16, 2022	Jun. 23, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Finance lease liabilities	$ 23,752			$ 14,742
Total long-term debt	2,485,402			2,162,164
NJNG
Debt Instrument [Line Items]
Less: Debt issuance costs	(9,528)			(9,093)
Less: Current maturities of long-term debt	(6,538)			(5,393)
Total long-term debt	1,307,069			1,098,494
NJNG | Finance lease obligation-meters
Debt Instrument [Line Items]
Finance lease liabilities	$ 30,290			20,135
NJNG | First mortgage bonds | Series OO
Debt Instrument [Line Items]
Stated interest rate	3.00%
Long-term debt	$ 46,500			46,500
NJNG | First mortgage bonds | Series PP
Debt Instrument [Line Items]
Stated interest rate	3.15%
Long-term debt	$ 50,000			50,000
NJNG | First mortgage bonds | Series QQ
Debt Instrument [Line Items]
Stated interest rate	3.58%
Long-term debt	$ 70,000			70,000
NJNG | First mortgage bonds | Series RR
Debt Instrument [Line Items]
Stated interest rate	4.61%
Long-term debt	$ 55,000			55,000
NJNG | First mortgage bonds | Series SS
Debt Instrument [Line Items]
Stated interest rate	2.82%
Long-term debt	$ 50,000			50,000
NJNG | First mortgage bonds | Series TT
Debt Instrument [Line Items]
Stated interest rate	3.66%
Long-term debt	$ 100,000			100,000
NJNG | First mortgage bonds | Series UU
Debt Instrument [Line Items]
Stated interest rate	3.63%
Long-term debt	$ 125,000			125,000
NJNG | First mortgage bonds | Series VV
Debt Instrument [Line Items]
Stated interest rate	4.01%
Long-term debt	$ 125,000			125,000
NJNG | First mortgage bonds | Series WW
Debt Instrument [Line Items]
Stated interest rate	3.50%
Long-term debt	$ 10,300			10,300
NJNG | First mortgage bonds | Series XX
Debt Instrument [Line Items]
Stated interest rate	3.38%
Long-term debt	$ 10,500			10,500
NJNG | First mortgage bonds | Series YY
Debt Instrument [Line Items]
Stated interest rate	2.45%
Long-term debt	$ 15,000			15,000
NJNG | First mortgage bonds | Series ZZ
Debt Instrument [Line Items]
Stated interest rate	3.76%
Long-term debt	$ 100,000			100,000
NJNG | First mortgage bonds | Series AAA
Debt Instrument [Line Items]
Stated interest rate	3.86%
Long-term debt	$ 85,000			85,000
NJNG | First mortgage bonds | Series BBB
Debt Instrument [Line Items]
Stated interest rate	2.75%
Long-term debt	$ 9,545			9,545
NJNG | First mortgage bonds | Series CCC
Debt Instrument [Line Items]
Stated interest rate	3.00%
Long-term debt	$ 41,000			41,000
NJNG | First mortgage bonds | Series DDD
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 50,000			50,000
NJNG | First mortgage bonds | Series EEE
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 50,000			50,000
NJNG | First mortgage bonds | Series FFF
Debt Instrument [Line Items]
Stated interest rate	3.33%
Long-term debt	$ 25,000			25,000
NJNG | First mortgage bonds | Series GGG
Debt Instrument [Line Items]
Stated interest rate	2.87%
Long-term debt	$ 25,000			25,000
NJNG | First mortgage bonds | Series HHH
Debt Instrument [Line Items]
Stated interest rate	2.97%
Long-term debt	$ 50,000			50,000
NJNG | First mortgage bonds | Series III
Debt Instrument [Line Items]
Stated interest rate	2.97%
Long-term debt	$ 50,000			0
NJNG | First mortgage bonds | Series JJJ
Debt Instrument [Line Items]
Stated interest rate	3.07%
Long-term debt	$ 50,000			0
NJNG | First mortgage bonds | Series LLL
Debt Instrument [Line Items]
Stated interest rate	4.37%
Long-term debt	$ 50,000			0
NJNG | First mortgage bonds | Series MMM
Debt Instrument [Line Items]
Stated interest rate	4.71%
Long-term debt	$ 50,000			0
NJR
Debt Instrument [Line Items]
Less: Debt issuance costs	(3,753)			(3,269)
Less: Current maturities of long-term debt	(50,000)			(50,000)
Total long-term debt	$ 1,066,247			956,731
NJR | Unsecured senior notes 3.25%
Debt Instrument [Line Items]
Stated interest rate	3.25%
Long-term debt	$ 0			50,000
NJR | Unsecured senior notes 3.20%
Debt Instrument [Line Items]
Stated interest rate	3.20%
Long-term debt	$ 50,000			50,000
NJR | Unsecured senior notes 3.48%
Debt Instrument [Line Items]
Stated interest rate	3.48%
Long-term debt	$ 100,000			100,000
NJR | Unsecured senior notes 3.54%
Debt Instrument [Line Items]
Stated interest rate	3.54%
Long-term debt	$ 100,000			100,000
NJR | Unsecured senior notes 3.96%
Debt Instrument [Line Items]
Stated interest rate	3.96%
Long-term debt	$ 100,000			100,000
NJR | Unsecured senior notes 3.29%
Debt Instrument [Line Items]
Stated interest rate	3.29%
Long-term debt	$ 150,000			150,000
NJR | Unsecured senior note 3.60%
Debt Instrument [Line Items]
Stated interest rate	3.60%
Long-term debt	$ 130,000			130,000
NJR | Unsecured senior note 3.50%
Debt Instrument [Line Items]
Stated interest rate	3.50%
Long-term debt	$ 130,000			130,000
NJR | Unsecured senior notes 3.25%
Debt Instrument [Line Items]
Stated interest rate	3.25%
Long-term debt	$ 80,000			80,000
NJR | Unsecured senior note 3.13%
Debt Instrument [Line Items]
Stated interest rate	3.13%
Long-term debt	$ 120,000			120,000
NJR | Unsecured senior notes 4.38%
Debt Instrument [Line Items]
Stated interest rate	4.38%		4.38%
Long-term debt	$ 110,000		$ 110,000	0
NJR | Unsecured senior notes 3.64%
Debt Instrument [Line Items]
Stated interest rate	3.64%	3.64%
Long-term debt	$ 50,000	$ 50,000		0
Clean Energy Ventures
Debt Instrument [Line Items]
Long-term debt	130,618			124,387
Less: Current maturities of long-term debt	(18,532)			(17,448)
Total Clean Energy Ventures long-term debt	$ 112,086			$ 106,939