REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 5,870,004	$ 5,722,278
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,028,362	5,850,079
Operating Segments | Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,844,036	3,707,461
Operating Segments | Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	970,599	914,788
Operating Segments | Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	248,112	365,423
Operating Segments | Storage and Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	965,615	862,407
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	136,300	162,134
Intercompany Assets
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (294,658)	$ (289,935)