Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	May. 05, 2015
Line of Credit Facility [Line Items]
Short-term Debt	$ 137.5	$ 38.0
Proceeds from note payable	4.0
Lenders under loans	140.9	41.6
Notes Payable to Bank	3.4	3.6
Senior unsecured notes	45.5	45.5
Debt and Capital Lease Obligations	$ 186.4	87.1
Debt Instrument, Interest Rate, Stated Percentage	8.50%
Debt Instrument, Call Feature, Redemption Price Percentage of Principal	100.00%
Debt Issuance Cost	$ 1.7
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	280.0
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	140.0
Lenders under loans	100.0	28.0
FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75.0		$ 50.0
Lenders under loans	15.0	0.0
FCStone LLC [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0.0
Lenders under loans	0.0	0.0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	40.0
Lenders under loans	22.5	10.0
INTL FCStone Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	25.0
Lenders under loans	$ 0.0	$ 0.0