Capital and Other Regulatory Requirements Level 4 - Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 110.0
Required Net Capital under Commodity Exchange Act	78.7
Net Capital	1,552.3
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,512.4
INTL Trading [Member]
Net Capital	2.0
Minimum Net Capital Required for Entity	1.0
FCC Investments [Member]
Net Capital	0.4
Minimum Net Capital Required for Entity	0.3
FCStone Australia [Member]
Net Capital under Commodity Exchange Act Computation	3.6
Required Net Capital under Commodity Exchange Act	0.9
Net Capital	12.0
Capital Required for Capital Adequacy	1.5
Risk Management Inc [Member]
Net Capital under Commodity Exchange Act Computation	0.4
Required Net Capital under Commodity Exchange Act	0.1
Hencorp Futures [Member]
Net Capital under Commodity Exchange Act Computation	0.6
Required Net Capital under Commodity Exchange Act	0.1
INTL FCStone Europe [Member]
Net Capital under Commodity Exchange Act Computation	25.1
Required Net Capital under Commodity Exchange Act	16.3
Net Capital	6.9
Cash and Securities Segregated under Commodity Exchange Act Regulation	6.9
FCStone Europe [Member]
Net Capital under Commodity Exchange Act Computation	1.5
Required Net Capital under Commodity Exchange Act	0.4
INTL Global Currencies [Member]
Net Capital under Commodity Exchange Act Computation	7.6
Required Net Capital under Commodity Exchange Act	1.0
TRX Futures [Member]
Net Capital	13.1
Capital Required for Capital Adequacy	$ 6.0