SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - NATURAL GAS IN STORAGE (Details) $ in Thousands	Dec. 31, 2020 USD ($) Bcf	Sep. 30, 2020 USD ($) Bcf
Inventory [Line Items]
Natural Gas in Storage, value | $	$ 163,169	$ 167,504
Natural Gas in Storage, Bcf | Bcf	55.9	61.52
Natural Gas Distribution
Inventory [Line Items]
Natural Gas in Storage, value | $	$ 98,434	$ 110,037
Natural Gas in Storage, Bcf | Bcf	25.1	27.2
Energy Services
Inventory [Line Items]
Natural Gas in Storage, value | $	$ 64,688	$ 57,352
Natural Gas in Storage, Bcf | Bcf	30.8	34.3
Storage and Transportation
Inventory [Line Items]
Natural Gas in Storage, value | $	$ 47	$ 115
Natural Gas in Storage, Bcf | Bcf	0	0.02