Inventories - Schedule of Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015
Public Utilities, Inventory
Total inventories	$ 27,009	$ 51,716	$ 33,376
Gas Utility natural gas
Public Utilities, Inventory
Total inventories	13,561	37,510	19,205
Materials, supplies and other
Public Utilities, Inventory
Total inventories	$ 13,448	$ 14,206	$ 14,171