SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) $ in Thousands	Jun. 30, 2019 USD ($) Bcf	Sep. 30, 2018 USD ($) Bcf
Inventory [Line Items]
Gas in Storage, value | $	$ 132,635	$ 184,633
Gas in Storage, Bcf | Bcf	42.9	59.0
Energy Services
Inventory [Line Items]
Gas in Storage, value | $	$ 59,354	$ 90,166
Gas in Storage, Bcf | Bcf	26.3	34.1
Natural Gas Distribution
Inventory [Line Items]
Gas in Storage, value | $	$ 73,281	$ 94,467
Gas in Storage, Bcf | Bcf	16.6	24.9