REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Billed	$ 109,366	$ 105,531
Unbilled	24,194	20,094
Customers’ credit balances and deposits	(31,297)	(38,595)	$ (44,910)
Total	102,263	87,030
Operating Segments | NJNG
Disaggregation of Revenue [Line Items]
Billed	75,789	51,613
Unbilled	14,817	11,839
Customers’ credit balances and deposits	(31,257)	(38,572)
Total	59,349	24,880
Operating Segments | CEV
Disaggregation of Revenue [Line Items]
Billed	6,818	8,441
Unbilled	9,377	8,255
Customers’ credit balances and deposits	0	0
Total	16,195	16,696
Operating Segments | ES
Disaggregation of Revenue [Line Items]
Billed	17,483	34,002
Unbilled	0	0
Customers’ credit balances and deposits	0	0
Total	17,483	34,002
Operating Segments | S&T
Disaggregation of Revenue [Line Items]
Billed	8,172	8,598
Unbilled	0	0
Customers’ credit balances and deposits	(40)	(23)
Total	8,132	8,575
Corporate, Non-Segment
Disaggregation of Revenue [Line Items]
Billed	1,104	2,877
Unbilled	0	0
Customers’ credit balances and deposits	0	0
Total	$ 1,104	$ 2,877