Receivables, net - Summary of Analysis of Allowance for Doubtful Trade Accounts Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Period	$ 46.8	$ 44.0	$ 48.6
Charged to Costs and Expenses	1.4	15.6	6.0
Deductions	(4.1)	(12.0)	(6.3)
Other Adjustments	1.3	(0.8)	(4.3)
Balance at End of Period	$ 45.4	$ 46.8	$ 44.0