Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Inventory [Line Items]
Agricultural Related Inventory	$ 65.9	$ 0.4
Precious Metals Inventory at fair value	5.3	10.8
Precious Metals Inventory at cost	52.6	21.6
Physical Commodities Inventory	$ 123.8	$ 32.8