Inventories - Schedule of Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Public Utilities, Inventory
Total inventories	$ 49,365	$ 51,716	$ 85,429
Gas Utility Natural Gas
Public Utilities, Inventory
Total inventories	35,923	37,510	72,442
Materials, Supplies and Other
Public Utilities, Inventory
Total inventories	$ 13,442	$ 14,206	$ 12,987