REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	$ 73,587	$ 40,086
Regulatory assets-noncurrent	584,830	500,666
Regulatory liability-current	32,287	31,090
Regulatory liabilities-noncurrent	180,458	185,634
NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	73,587	40,086
Regulatory assets-noncurrent	579,599	495,300
Regulatory liability-current	30,637	25,779
Regulatory liabilities-noncurrent	180,458	185,634
Adelphia
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	5,231	5,366
Regulatory liability-current	1,650	5,311
Overrecovered natural gas costs | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory liability-current	30,637	17,807
Derivatives at fair value, net | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory liability-current	0	7,972
Regulatory liabilities-noncurrent	0	116
Tax Act impact | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	180,347	185,367
Other noncurrent regulatory liabilities | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	111	151
New Jersey Clean Energy Program | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	15,804	15,697
Conservation Incentive Program | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	50,356	23,099
Derivatives at fair value, net | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	6,017	0
Other current regulatory assets | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	1,410	1,290
Regulatory assets-noncurrent	51,019	45,828
Expended, net of recoveries
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	66,300
Expended, net of recoveries | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	66,298	66,149
Liability for future expenditures | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	169,390	127,070
Deferred income taxes | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	41,667	40,520
SAVEGREEN | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	83,589	52,690
Postemployment and other benefit costs | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	55,274	56,021
Deferred storm damage costs | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	0	2,172
Cost of removal | NJNG
Schedule of Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	$ 112,362	$ 104,850