Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Unrecognized Tax Benefits
Balance at beginning of year	$ 90.2	$ 83.8	$ 93.1
Additions for tax positions of the current year	47.5	12.5	4.7
Additions for tax positions of prior years	16.1	2.9	3.0
Reductions for tax positions of prior years	(4.0)	0.0	(2.2)
Settlements	(2.0)	(5.6)	(0.6)
Statute of limitations expiration	(3.2)	(2.9)	(8.3)
Foreign currency translation adjustment increase	1.8
Foreign currency translation adjustment decrease		(0.5)	(5.9)
Balance at End of Year	$ 146.4	$ 90.2	$ 83.8