SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) $ in Thousands	Sep. 30, 2019 USD ($) Bcf	Sep. 30, 2018 USD ($) Bcf
Public Utilities, Inventory [Line Items]
Gas in Storage | $	$ 169,803	$ 184,633
Bcf | Bcf	52.6	59.0
Energy Services
Public Utilities, Inventory [Line Items]
Gas in Storage | $	$ 52,390	$ 90,166
Bcf | Bcf	25.6	34.1
Natural Gas Distribution
Public Utilities, Inventory [Line Items]
Gas in Storage | $	$ 117,413	$ 94,467
Bcf | Bcf	27.0	24.9