SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) $ in Thousands	Dec. 31, 2019 USD ($) Bcf	Sep. 30, 2019 USD ($) Bcf
Inventory [Line Items]
Gas in Storage, value | $	$ 186,895	$ 169,803
Gas in Storage, Bcf | Bcf	59.9	52.6
Energy Services
Inventory [Line Items]
Gas in Storage, value | $	$ 83,908	$ 52,390
Gas in Storage, Bcf | Bcf	36.0	25.6
Natural Gas Distribution
Inventory [Line Items]
Gas in Storage, value | $	$ 102,987	$ 117,413
Gas in Storage, Bcf | Bcf	23.9	27.0