Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 133.1
Required Net Capital under Commodity Exchange Act	73.2
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,869.7
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	1,838.2
Secured Funds	60.9
Secured Funds Required Under Commodity Exchange Act	44.7
Forward Insight Commodities [Member]
Net Capital under Commodity Exchange Act Computation	0.2
Required Net Capital under Commodity Exchange Act	0.1
INTL FCStone Ltd [Member]
Net Capital under Commodity Exchange Act Computation	59.5
Required Net Capital under Commodity Exchange Act	49.4
Cash and Securities Segregated under Commodity Exchange Act Regulation	128.1
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	127.9
INTL Global Currencies [Member]
Net Capital under Commodity Exchange Act Computation	20.4
Required Net Capital under Commodity Exchange Act	1.2
INTL Trading [Member]
Net Capital	3.6
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	1.5
Required Net Capital under Commodity Exchange Act	0.9
Net Capital	11.4
Cash and Securities Segregated under Commodity Exchange Act Regulation	28.1
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	21.7
Capital Required for Capital Adequacy	4.4
INTL FCStone DTVM Ltda [Member]
Net Capital	1.3
Capital Required for Capital Adequacy	0.7
INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain]
Net Capital	8.9
Capital Required for Capital Adequacy	0.1
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	8.7
Required Net Capital under Commodity Exchange Act	6.3
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	3.6
Required Net Capital under Commodity Exchange Act	$ 0.2