Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 126.3
Required Net Capital under Commodity Exchange Act	64.1
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,781.5
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	1,734.2
Secured Funds	62.3
Secured Funds Required Under Commodity Exchange Act	44.0
INTL FCStone Ltd [Member]
Net Capital under Commodity Exchange Act Computation	98.0
Required Net Capital under Commodity Exchange Act	57.3
Cash and Securities Segregated under Commodity Exchange Act Regulation	87.0
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	87.0
INTL Trading [Member]
Net Capital	5.0
Minimum Net Capital Required for Entity	1.0
FCC Investments [Member]
Net Capital	0.3
Minimum Net Capital Required for Entity	0.3
INTL FCStone Partners LP [Member]
Net Capital	25.9
Minimum Net Capital Required for Entity	9.4
FCStone Australia [Member]
Net Capital under Commodity Exchange Act Computation	1.5
Required Net Capital under Commodity Exchange Act	0.8
Net Capital	11.5
Cash and Securities Segregated under Commodity Exchange Act Regulation	17.9
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	11.9
Capital Required for Capital Adequacy	3.8
INTL FCStone DTVM Ltda [Member]
Net Capital	2.6
Capital Required for Capital Adequacy	0.5
Gainvest S.A. Sociedad Gerente de FCI - Comision Nacional de Valores [Member]
Net Capital under Commodity Exchange Act Computation	0.3
Required Net Capital under Commodity Exchange Act	0.1
Net Capital	5.1
Capital Required for Capital Adequacy	0.2
INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain]
Net Capital	10.1
Capital Required for Capital Adequacy	8.0
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	4.3
Required Net Capital under Commodity Exchange Act	1.7
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	5.5
Required Net Capital under Commodity Exchange Act	$ 0.8

Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated

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- Definition

Secured funds

+ References

No definition available.

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- Definition

Secured Funds Required Under Commodity Exchange Act

+ References

No definition available.

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- Definition

The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 505

-Section 50

-Paragraph 1H

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7881181&loc=d3e65071-112826

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 505

-Section 50

-Paragraph 1

-Subparagraph (c)(1)

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- Definition

Cash and securities deposited in a special reserve account for the exclusive benefit of customers pursuant to the Commodity Exchange Act.

+ References

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- Definition

Minimum amount of net capital required to be maintained by the entity to engage in securities transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Rule 15c3

-Number 240

-Section 1

-Paragraph 1

-Subparagraph i

-Article 15c3

-Subsection a

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Net capital is equal to the net worth of the broker dealer, less certain items such as exchange memberships, carrying value of securities not readily marketable, haircuts on marketable securities in proprietary accounts, furniture and equipment and other illiquid assets as defined.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Rule 15c3

-Number 240

-Section 1

-Paragraph 1

-Subparagraph ii

-Article 15c3

-Subsection a

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- Definition

The amount of net capital calculated under the Commodity Futures Trading Commission's minimum financial requirements, pursuant to the Commodity Exchange Act, less the market value of certain commodity options.

+ References

No definition available.

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Amount of net capital required to be maintained under the Commodity Futures Trading Commission's (CFTC) minimum financial requirements, pursuant to the Commodity Exchange Act, less the market value of certain commodity options.

+ References

No definition available.

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