Segment and Geographic Information - Total Revenues by Geographic Location (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Revenues	$ 2,628.4	$ 3,995.1	$ 14,442.0	$ 13,627.7	$ 10,655.7	$ 7,005.1	$ 8,452.9	$ 7,908.7	$ 34,693.2	$ 34,022.4	$ 42,493.4
Gross Profit	178.7	$ 151.6	$ 156.5	$ 137.5	130.6	$ 118.2	$ 129.2	$ 112.9	624.3	490.9	468.2
Long-Lived Assets	19.7				15.9				19.7	15.9	17.5
UNITED STATES
Revenues									25,959.0	19,055.3	27,788.0
Gross Profit									424.3	330.4	323.9
Long-Lived Assets	13.8				8.5				13.8	8.5	9.1
Europe [Member]
Revenues									121.2	86.0	65.6
Gross Profit									125.0	86.0	65.6
Long-Lived Assets	4.0				5.0				4.0	5.0	5.4
South America [Member]
Revenues									49.0	53.2	51.3
Gross Profit									49.0	53.2	51.3
Long-Lived Assets	1.7				2.0				1.7	2.0	2.4
Asia [Member]
Revenues									8,560.0	14,822.4	14,581.2
Gross Profit									21.9	15.8	20.1
Long-Lived Assets	0.2				0.3				0.2	0.3	0.5
Other (geographic location) [Member]
Revenues									4.0	5.5	7.3
Gross Profit									4.1	5.5	7.3
Long-Lived Assets	$ 0.0				$ 0.1				$ 0.0	$ 0.1	$ 0.1