Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended						12 Months Ended		12 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Main line of credit facilities [Member]	Sep. 30, 2012 Main line of credit facilities [Member]	Sep. 30, 2013 INTL COM line of credit facility [Member]	Sep. 30, 2012 INTL COM line of credit facility [Member]	Sep. 30, 2013 HCO Syndicated line of credit facility [Member] Rate	Sep. 30, 2012 HCO Syndicated line of credit facility [Member]	Sep. 30, 2013 FCS Margin line of credit facility [Member] Rate	Sep. 30, 2012 FCS Margin line of credit facility [Member]	Sep. 30, 2013 FMS Sub-note commodity line of credit facility [Member] Rate	Sep. 30, 2012 FMS Sub-note commodity line of credit facility [Member]	Nov. 15, 2013 INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End							3.72%		5.25%		3.75%
Line of Credit Facility, Maximum Borrowing Capacity			$ 290.0	$ 150.0	$ 0		$ 140.0		$ 75.0		$ 75.0		$ 25.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage							0.625%		0.50%		0.50%
Line of Credit Facility, Amount Outstanding	61.0	218.2			0	107.0	55.0	48.0	0	20.0	6.0	43.2
Senior Notes	45.5	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						1.5
Debt and Capital Lease Obligations	$ 106.5	$ 218.2