REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	$ 122,589	$ 40,086
Total current regulatory liabilities	15,681	31,090
Regulatory liabilities-noncurrent	183,941	185,634
NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	122,589	40,086
Regulatory assets-noncurrent	496,546	495,300
Total current regulatory liabilities	12,862	25,779
Regulatory liabilities-noncurrent	183,941	185,634
NJNG | Overrecovered natural gas costs
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	12,785	17,807
NJNG | Derivatives at fair value, net
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	77	7,972
Regulatory liabilities-noncurrent	602	116
NJNG | Tax Act impact
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	182,857	185,367
NJNG | Other noncurrent regulatory liabilities
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	482	151
NJNG | New Jersey Clean Energy Program
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	6,191	15,697
NJNG | Conservation Incentive Program
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	46,903	23,099
NJNG | Derivatives at fair value, net
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	68,241	0
NJNG | Other current regulatory assets
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	1,254	1,290
Regulatory assets-noncurrent	41,769	45,828
NJNG | Expended, net of recoveries
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	63,256	66,149
NJNG | Liability for future expenditures
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	124,493	127,070
NJNG | Deferred income taxes
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	41,213	40,520
NJNG | SAVEGREEN
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	57,203	52,690
NJNG | Postemployment and other benefit costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	55,925	56,021
NJNG | Deferred storm damage costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	1,086	2,172
NJNG | Cost of removal
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	111,601	104,850
Adelphia
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	5,283	5,366
Total current regulatory liabilities	$ 2,819	$ 5,311