Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 17, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Unrecognized Tax Benefits
Balance at beginning of year		$ 146.4	$ 90.2	$ 83.8
Additions for tax positions of the current year		26.4	47.5	12.5
Additions for tax positions of prior years		119.2	16.1	2.9
Reductions for tax positions of prior years		(41.3)	(4.0)	0.0
Settlements	$ (43.1)	(14.2)	(2.0)	(5.6)
Statute of limitations expiration		(2.6)	(3.2)	(2.9)
Foreign currency translation		(0.3)		(0.5)
Foreign currency translation			1.8
Balance at End of Year		$ 233.6	$ 146.4	$ 90.2