Income Taxes - Other Additional Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at beginning of year	$ 27.0	$ 33.5	$ 37.0
Additions for tax positions related to current year	7.6	4.6	7.0
Additions for tax positions related to prior years	8.4	2.1	5.2
Reductions for tax positions of prior years	(1.1)	0.0	(2.6)
Settlements	(3.0)	(8.6)	(10.1)
Lapse of statute of limitations	(1.5)	(4.5)	(3.0)
Unrecognized Tax Benefits, Decrease Resulting from Foreign Currency Translation	0.0	(0.1)	0.0
Balance at end of year	37.4	27.0	33.5
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	2.4
Net unrecognized tax benefits, excluding interest and penalties that would affect the Company's net income if recognized	19.0
Accruals for payment of interest and penalties	10.0	12.0
Interest and penalties	$ (1.2)	$ (3.0)	$ 1.5