Income Taxes - Schedule of Income Tax Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Components of income before income taxes
United States									$ 280.8	$ 721.6	$ 547.2
Non-United States									620.2	609.2	490.2
Total	$ 56.4	$ 321.4	$ 402.4	$ 120.8	$ 481.7	$ 251.7	$ 299.6	$ 297.8	901.0	1,330.8	1,037.4
Current income tax provision:
United States									105.6	475.3	67.3
Non-United States									112.1	131.4	109.9
State and local									16.5	18.1	0.7
Total current									234.2	624.8	177.9
Deferred income tax provision:
United States									(27.0)	118.6	44.6
Non-United States									(0.1)	48.0	(14.1)
State and local									(1.9)	3.9	3.3
Total deferred									(29.0)	170.5	33.8
Income tax provision									205.2	795.3	211.7
Total income taxes paid									$ 293.3	$ 222.9	$ 211.9