DEI Document (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Mar. 31, 2012	May 04, 2012	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-Q
Document Period End Date	Mar. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,129,017
Entity Well-Know Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 295.7