Credit Facilities - Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2013
Line of Credit Facility [Line Items]
Senior Notes	$ 45.5	$ 45.5
Debt Instrument, Interest Rate, Stated Percentage		8.50%
Debt Instrument, Call Feature, Redemption Price Percentage of Principal		100.00%
Debt Issuance Cost	1.7
Line of Credit Facility, Amount Outstanding	61.0	60.2
Debt and Capital Lease Obligations	106.5	105.7
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		315.0
Line of Credit Facility, Current Borrowing Capacity		175
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, Amount Outstanding	55.0	49.0
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, Amount Outstanding	0	0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		75.0
Line of Credit Facility, Amount Outstanding	6.0	11.2
INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		25.0
Line of Credit Facility, Amount Outstanding	$ 0	$ 0