REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	$ 42,320	$ 30,118
Total current regulatory liabilities	50,574	28,007
Regulatory liabilities-noncurrent	189,876	193,051
NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	42,320	29,701
Regulatory assets-noncurrent	524,473	519,600
Total current regulatory liabilities	50,008	28,007
Regulatory liabilities-noncurrent	186,839	191,888
Adelphia
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	0	417
Regulatory assets-noncurrent	5,083	2,499
Total current regulatory liabilities	566	0
Regulatory liabilities-noncurrent	3,037	1,163
Total current regulatory liabilities | NJNG
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	20,630	5,510
Derivatives at fair value, net | NJNG
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	29,378	22,497
Regulatory liabilities-noncurrent	0	1,166
Tax Act impact | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	186,621	190,386
Other noncurrent regulatory liabilities | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	218	336
New Jersey Clean Energy Program | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	17,648	16,308
Conservation Incentive Program | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	23,187	11,839
Other current regulatory assets | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	1,485	1,554
Regulatory assets-noncurrent	37,305	32,695
Expended, net of recoveries | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	65,632	58,483
Liability for future expenditures | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	120,597	135,012
Deferred income taxes | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	40,274	39,694
Derivatives at fair value, net | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	5,057	0
SAVEGREEN | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	39,474	32,941
Postemployment and other benefit costs | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	109,320	117,194
Deferred storm damage costs | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	2,714	4,343
Cost of removal | NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	$ 104,100	$ 99,238