Income Taxes (Details 4) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Unrecognized tax benefits, excluding interest and penalties
Gross unrecognized tax benefits balance at beginning of year	$ 32.4	$ 43.9	$ 38.9
Additions based on tax positions related to the current year	1.9	2.3	2.1
Additions based on tax positions related to prior years	10.8	14.9	11.6
Reductions based on tax positions related to prior years	(0.1)	0.0	(1.0)
Reductions related to settlements with taxing authorities	(7.7)	(27.1)	(4.3)
Reductions related to lapses of statute of limitations	(6.3)	(1.6)	(1.6)
Effect of foreign currency translation	0.1
Effect of foreign currency translation		0.0	(1.8)
Gross unrecognized tax benefits balance at end of year	$ 31.1	$ 32.4	$ 43.9