SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) $ in Thousands	Mar. 31, 2018 USD ($) Bcf	Sep. 30, 2017 USD ($) Bcf
Inventory [Line Items]
Gas in Storage, value | $	$ 71,169	$ 202,063
Gas in Storage, Bcf | Bcf	23.3	75.7
Energy Services
Inventory [Line Items]
Gas in Storage, value | $	$ 51,915	$ 122,884
Gas in Storage, Bcf | Bcf	18.6	53.9
Natural Gas Distribution
Inventory [Line Items]
Gas in Storage, value | $	$ 19,254	$ 79,179
Gas in Storage, Bcf | Bcf	4.7	21.8