REGULATION - ADDITIONAL INFORMATION (Details) $ in Thousands															1 Months Ended					11 Months Ended	12 Months Ended
	Oct. 31, 2025 USD ($)	Sep. 26, 2025 USD ($)	Sep. 25, 2025 USD ($)	Sep. 05, 2025 USD ($)	May 30, 2025 USD ($)	May 21, 2025 USD ($)	Dec. 18, 2024 USD ($)	Nov. 21, 2024 USD ($)	Oct. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 25, 2024 USD ($)	Jul. 26, 2024 USD ($)	Jun. 28, 2024 USD ($)	Mar. 28, 2024 USD ($)	Apr. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Mar. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)	Feb. 28, 2019 USD ($) projectComponent	Sep. 30, 2025 USD ($)	Sep. 30, 2025 USD ($) filing	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Schedule of Regulatory Filings [Line Items]
Number of interim filings during each fiscal year | filing																					2
Number of days notice for refund																					5 days
Revenues from contracts with customers																					$ 1,351,305	$ 1,229,949	$ 1,111,520
NJNG
Schedule of Regulatory Filings [Line Items]
Approved rate increase (decrease), amount				$ 33,100										$ 43,500
Interim rate increase (decrease), amount												$ 41,200
Environmental Remediation Costs
Schedule of Regulatory Filings [Line Items]
Regulatory assets, amortization period																				7 years	7 years
Base Rate Stipulation
Schedule of Regulatory Filings [Line Items]
Weighted average cost of capital																					7.08%
Approved equity capital structure, percentage																					54.00%
Public utilities, approved depreciation rate, percentage																					3.21%
BPU
Schedule of Regulatory Filings [Line Items]
Approved return on equity																					9.60%
Approved rate increase (decrease), amount															$ 76,900
Capital investments approved by the BPU									$ 205,000
Financing options									160,500
Operations and maintenance expense									20,100
Total amount									$ 385,600											$ 12,300
BPU | NJNG
Schedule of Regulatory Filings [Line Items]
Approved rate increase (decrease), amount								$ 157,000
BPU | NJNG
Schedule of Regulatory Filings [Line Items]
Approved rate increase (decrease), amount				$ 4,000							$ 4,700
Annual recovery increase			$ (1,000)										$ 6,800
SAVEGREEN
Schedule of Regulatory Filings [Line Items]
Public utility extension term																	3 years
Capital investments approved by the BPU																	$ 126,100
Financing options																	109,400
Operations and maintenance expense																	$ 23,400
Annual recovery increase					$ 17,300		$ 3,100
SAVEGREEN | Minimum
Schedule of Regulatory Filings [Line Items]
Regulatory assets, amortization period																				3 years	3 years
Program recovery term																					3 years
SAVEGREEN | Maximum
Schedule of Regulatory Filings [Line Items]
Regulatory assets, amortization period																				10 years	10 years
Program recovery term																					10 years
BGSS
Schedule of Regulatory Filings [Line Items]
Requested rate increase (decrease), amount					63,300	$ (31,000)
BGSS Balancing
Schedule of Regulatory Filings [Line Items]
Requested rate increase (decrease), amount					6,100	40,300
Conservation Incentive Program
Schedule of Regulatory Filings [Line Items]
Requested rate increase (decrease), amount					$ (25,500)	$ (800)
NJNG | Subsequent Event
Schedule of Regulatory Filings [Line Items]
Revenues from contracts with customers	$ 38,100
RAC
Schedule of Regulatory Filings [Line Items]
Approved rate increase (decrease), amount		$ (900)								$ 2,400						$ 2,400
NJCEP
Schedule of Regulatory Filings [Line Items]
Approved rate increase (decrease), amount		$ (5,000)								$ 1,600						$ 5,500
Infrastructure Investment Program (IIP) | NJNG
Schedule of Regulatory Filings [Line Items]
Program recovery term																		5 years	5 years
Number of project components | projectComponent																			2
Public utilities, investments																		$ 150,000	$ 507,000