Inventories - Schedule of Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Sep. 30, 2016	Mar. 31, 2016
Public Utilities, Inventory
Total inventories	$ 17,174	$ 42,340	$ 16,685
Gas Utility natural gas
Public Utilities, Inventory
Total inventories	2,394	29,223	3,786
Materials, supplies and other
Public Utilities, Inventory
Total inventories	$ 14,780	$ 13,117	$ 12,899