Credit Facilities - Number of Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014
Line of Credit Facility [Line Items]
Debt Issuance Cost	$ 1.7
Number of credit facilities	4
INTL FCStone Europe [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	25.0
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	270.0
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	140.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.625%
Line of Credit Facility, Interest Rate at Period End	5.25%
Debt Issuance Cost	1.5
FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.50%
Line of Credit Facility, Interest Rate at Period End	5.25%
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 30.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.50%
Line of Credit Facility, Interest Rate at Period End	3.70%
Eurodollar Rate [Member] | HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.00%
Base Rate [Member] | INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.50%
Base Rate [Member] | HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Base Rate [Member] | FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%