Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 106.9
Required Net Capital under Commodity Exchange Act	63.3
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,606.1
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	1,582.7
Secured Funds	69.0
Secured Funds Required Under Commodity Exchange Act	52.4
INTL FCStone Europe [Member]
Net Capital under Commodity Exchange Act Computation	59.7
Required Net Capital under Commodity Exchange Act	25.8
Net Capital	65.4
Cash and Securities Segregated under Commodity Exchange Act Regulation	64.2
INTL Global Currencies [Member]
Net Capital under Commodity Exchange Act Computation	20.5
Required Net Capital under Commodity Exchange Act	0.5
INTL Trading [Member]
Net Capital	4.8
Minimum Net Capital Required for Entity	1.0
FCC Investments [Member]
Net Capital	0.3
Minimum Net Capital Required for Entity	0.3
FCStone Australia [Member]
Net Capital under Commodity Exchange Act Computation	1.7
Required Net Capital under Commodity Exchange Act	0.9
Net Capital	11.5
Capital Required for Capital Adequacy	4.1
INTL FCStone DTVM Ltda [Member]
Net Capital	1.0
Capital Required for Capital Adequacy	0.6
INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain]
Net Capital	5.7
Capital Required for Capital Adequacy	0.1
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	7.6
Required Net Capital under Commodity Exchange Act	6.7
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	6.4
Required Net Capital under Commodity Exchange Act	$ 0.2