Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	May. 05, 2015	Sep. 30, 2014
Line of Credit Facility [Line Items]
Short-term Debt	$ 71.2
Proceeds from note payable	4.0	$ 0.0
Lenders under loans and overdrafts	75.0			$ 22.5
Notes Payable to Bank	3.8			0.0
Senior unsecured notes	45.5			45.5
Debt and Capital Lease Obligations	$ 120.5			68.0
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
Line of Credit Facility, Current Borrowing Capacity	140.0
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 and overdrafts	50.0			15.0
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 and overdrafts	14.0			0.0
FCStone LLC [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0.0
Lenders under loans and overdrafts	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 and overdrafts	7.2			7.5
INTL FCStone Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	25.0
Lenders under loans and overdrafts	$ 0.0			$ 0.0