Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 106.2
Required Net Capital under Commodity Exchange Act	66.2
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,638.6
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	1,617.2
Secured Funds	66.1
Secured Funds Required Under Commodity Exchange Act	56.2
INTL Trading [Member]
Net Capital	4.3
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	3.9
INTL FCStone Europe [Member]
Net Capital under Commodity Exchange Act Computation	50.6
Required Net Capital under Commodity Exchange Act	20.5
Net Capital	53.7
Cash and Securities Segregated under Commodity Exchange Act Regulation	51.8
FCStone Europe [Member]
Net Capital under Commodity Exchange Act Computation	1.9
Required Net Capital under Commodity Exchange Act	0.6
INTL FCStone DTVM Ltda [Member]
Net Capital	0.8
Capital Required for Capital Adequacy	0.7
INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain]
Net Capital	3.2
Capital Required for Capital Adequacy	0.1
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	7.8
Required Net Capital under Commodity Exchange Act	5.8
INTL Global Currencies [Member]
Net Capital under Commodity Exchange Act Computation	19.4
Required Net Capital under Commodity Exchange Act	1.0
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	3.4
Required Net Capital under Commodity Exchange Act	$ 0.3