REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 6,981,645	$ 6,537,496	$ 6,261,416
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	7,081,575	6,679,140	6,378,335
Operating Segments | NJNG
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,789,835	4,414,829	4,030,686
Operating Segments | CEV
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,157,573	1,128,577	1,015,065
Operating Segments | ES
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	108,710	123,775	333,064
Operating Segments | S&T
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,025,457	1,011,959	999,520
Corporate, Non-Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	159,444	171,275	159,068
Consolidation, Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (259,374)	$ (312,919)	$ (275,987)