REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 6,261,416	$ 5,722,278	$ 5,316,477
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,378,335	5,850,079	5,435,389
Operating Segments | Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,030,686	3,707,461	3,531,477
Operating Segments | Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,015,065	914,788	814,277
Operating Segments | Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	333,064	365,423	244,836
Operating Segments | Storage and Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	999,520	862,407	844,799
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	159,068	162,134	138,375
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (275,987)	$ (289,935)	$ (257,287)