Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2013	Sep. 30, 2015	May 05, 2015
Line of Credit Facility [Line Items]
Short-term Debt	$ 208.6			$ 38.0
Proceeds from note payable	0.0	$ 4.0
Lenders under loans	211.6			41.6
Notes Payable to Bank	3.0			3.6
Senior unsecured notes	45.5			45.5
Debt and Capital Lease Obligations	$ 257.1			87.1
Debt Instrument, Interest Rate, Stated Percentage	8.50%
Debt Instrument, Call Feature, Redemption Price Percentage of Principal	100.00%
Debt Issuance Cost	$ 1.8		$ 1.7
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	165.0
Line of Credit Facility, Maximum Borrowing Capacity	385.0
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	220.0
Lenders under loans	170.0			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	0.0			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	65.0
Lenders under loans	38.6			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