REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 6,312,580	$ 6,261,416
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,461,292	6,378,335
Operating Segments | Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,239,231	4,030,686
Operating Segments | Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,091,029	1,015,065
Operating Segments | Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	126,903	333,064
Operating Segments | Storage and Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,004,129	999,520
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	151,430	159,068
Intercompany Assets
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (300,142)	$ (275,987)