Segment and Geographic Information - Total Revenues by Geographic Location (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenues	$ 12,382.5	$ 5,505.9	$ 5,460.8	$ 6,074.4	$ 2,777.6	$ 4,868.5	$ 3,708.9	$ 3,399.9	$ 29,423.6	$ 14,754.9	$ 34,693.2
Gross Profit	205.1	$ 197.6	$ 195.8	$ 185.5	178.6	$ 175.0	$ 166.1	$ 151.3	784.0	671.0	624.3
Long-Lived Assets	38.7				29.4				38.7	29.4	19.7
UNITED STATES
Revenues									1,168.0	817.1	25,959.0
Gross Profit									529.4	457.0	424.3
Long-Lived Assets	29.7				23.3				29.7	23.3	13.8
Europe [Member]
Revenues									166.9	463.5	121.2
Gross Profit									166.9	120.2	125.0
Long-Lived Assets	7.3				4.8				7.3	4.8	4.0
South America [Member]
Revenues									53.9	64.8	49.0
Gross Profit									54.0	64.8	49.0
Long-Lived Assets	1.5				1.2				1.5	1.2	1.7
Asia [Member]
Revenues									28,030.3	13,405.1	8,560.0
Gross Profit									29.2	24.6	21.9
Long-Lived Assets	$ 0.2				$ 0.1				0.2	0.1	0.2
Other (geographic location) [Member]
Revenues									4.5	4.4	4.0
Gross Profit									$ 4.5	$ 4.4	$ 4.1