DEI Document (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2011	Dec. 09, 2011	Mar. 31, 2011
Document Information [Line Items]
Entity Registrant Name	INTL FCSTONE INC.
Entity Central Index Key	0000913760
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Common Stock, Shares Outstanding		18,742,025
Entity Well-Know Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 295.7