v3.26.1
REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Sep. 30, 2025
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current $ 31,954 $ 48,898
Regulatory assets-noncurrent 619,754 672,518
Regulatory liability-current 72,350 12,884
Regulatory liabilities-noncurrent 168,990 171,177
NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 31,954 48,898
Regulatory assets-noncurrent 614,781 667,308
Regulatory liability-current 69,852 10,643
Regulatory liabilities-noncurrent 168,990 171,177
NJNG | Overrecovered natural gas costs    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liability-current 41,993 10,643
NJNG | Conservation Incentive Program    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liability-current 27,859 0
NJNG | Tax Act impact    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liabilities-noncurrent 167,800 170,309
NJNG | Other noncurrent regulatory liabilities    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory liabilities-noncurrent 1,190 868
Adelphia Gateway, LLC    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 4,973 5,210
Regulatory liability-current 2,498 2,241
New Jersey Clean Energy Program | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 6,930 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 23,731 7,544
Other current regulatory assets | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-current 1,293 1,486
Regulatory assets-noncurrent 47,474 63,612
Expended, net of recoveries    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 61,200  
Expended, net of recoveries | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 61,245 74,961
Liability for future expenditures | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 166,110 166,990
Deferred income taxes | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 48,117 46,013
SAVEGREEN | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 120,133 141,562
Postemployment and other benefit costs | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent 42,131 41,275
Cost of removal | NJNG    
Schedule of Regulatory Assets And Liabilities [Line Items]    
Regulatory assets-noncurrent $ 129,571 $ 132,895