Inventories - Components of Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2014
Inventory
Inventory, net	$ 208.7	$ 423.0	$ 332.0
Non-utility LPG and Natural Gas
Inventory
Inventory, net	124.6	283.6	222.6
Gas Utility Natural Gas
Inventory
Inventory, net	19.2	82.7	45.7
Materials, Supplies and Other
Inventory
Inventory, net	$ 64.9	$ 56.7	$ 63.7