Acquisitions Acquisitions (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Gross Profit	$ 151.3	$ 137.5
Net income	$ 8.8	$ 9.4
Earnings Per Share, Basic		$ 0.50
Earnings Per Share, Diluted		$ 0.49
G.X. Clarke (INTL FCStone Partners) [Member]
Gross Profit		$ 8.7
Net income		$ 0.7
Earnings Per Share, Basic		$ 0.04
Earnings Per Share, Diluted		$ 0.04
INTL FCStone Inc. [Member]
Gross Profit		$ 146.2
Net income		$ 10.1
Earnings Per Share, Basic		$ 0.54
Earnings Per Share, Diluted		$ 0.53