REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Billed	$ 211,036	$ 105,531
Unbilled	117,280	20,094
Customers' credit balances and deposits	(42,587)	(38,595)	$ (45,461)	$ (44,910)
Customers accounts receivables & Customers' credit balances and deposits	285,729	87,030
Operating Segments | NJNG
Disaggregation of Revenue [Line Items]
Billed	138,967	51,613
Unbilled	112,000	11,839
Customers' credit balances and deposits	(42,565)	(38,572)
Customers accounts receivables & Customers' credit balances and deposits	208,402	24,880
Operating Segments | CEV
Disaggregation of Revenue [Line Items]
Billed	8,171	8,441
Unbilled	5,280	8,255
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	13,451	16,696
Operating Segments | ES
Disaggregation of Revenue [Line Items]
Billed	52,677	34,002
Unbilled	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	52,677	34,002
Operating Segments | S&T
Disaggregation of Revenue [Line Items]
Billed	8,455	8,598
Unbilled	0	0
Customers' credit balances and deposits	(22)	(23)
Customers accounts receivables & Customers' credit balances and deposits	8,433	8,575
Corporate, Non-Segment
Disaggregation of Revenue [Line Items]
Billed	2,766	2,877
Unbilled	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	$ 2,766	$ 2,877