v3.26.1
REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current $ 32,229 $ 48,898
Regulatory assets-noncurrent 650,105 672,518
Regulatory liability-current 70,082 12,884
Regulatory liabilities-noncurrent 167,403 171,177
NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 31,733 48,898
Regulatory assets-noncurrent 645,147 667,308
Regulatory liability-current 68,136 10,643
Regulatory liabilities-noncurrent 167,403 171,177
NJNG | Overrecovered natural gas costs    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liability-current 45,310 10,643
NJNG | Conservation Incentive Program    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liability-current 22,826 0
NJNG | Tax Act impact    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liabilities-noncurrent 166,545 170,309
NJNG | Other noncurrent regulatory liabilities    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liabilities-noncurrent 858 868
Adelphia Gateway, LLC    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 496 0
Regulatory assets-noncurrent 4,958 5,210
Regulatory liability-current 1,946 2,241
New Jersey Clean Energy Program | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 14,588 17,171
Conservation Incentive Program | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 0 22,697
Derivatives at fair value, net | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 15,530 7,544
Other current regulatory assets | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 1,615 1,486
Regulatory assets-noncurrent 52,361 63,612
Expended, net of recoveries    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 60,700  
Expended, net of recoveries | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 60,694 74,961
Liability for future expenditures | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 165,170 166,990
Deferred income taxes | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 49,300 46,013
SAVEGREEN | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 148,087 141,562
Postemployment and other benefit costs | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 42,560 41,275
Cost of removal | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent $ 126,975 $ 132,895