SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) $ in Thousands	Jun. 30, 2020 USD ($) Bcf	Sep. 30, 2019 USD ($) Bcf
Inventory [Line Items]
Gas in Storage, value | $	$ 123,962	$ 169,803
Gas in Storage, Bcf | Bcf	50.6	52.6
Energy Services
Inventory [Line Items]
Gas in Storage, value | $	$ 50,400	$ 52,390
Gas in Storage, Bcf | Bcf	33.1	25.6
Natural Gas Distribution
Inventory [Line Items]
Gas in Storage, value | $	$ 73,501	$ 117,413
Gas in Storage, Bcf | Bcf	17.5	27.0
Midstream
Inventory [Line Items]
Gas in Storage, value | $	$ 61	$ 0
Gas in Storage, Bcf | Bcf	0	0