REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 6,161,921	$ 5,722,278
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,310,129	5,850,079
Operating Segments | Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,959,609	3,707,461
Operating Segments | Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	994,762	914,788
Operating Segments | Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	370,233	365,423
Operating Segments | Storage and Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	985,525	862,407
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	139,652	162,134
Intercompany Assets
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (287,860)	$ (289,935)