Financial Instruments and Risk Management - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation	$ (27.1)	$ (29.0)
Exit lease liability	(0.7)	(0.6)
Net Liabilities at estimated fair value	(23.7)	(17.7)
Foreign currency contracts | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	(0.2)	(0.1)
Foreign currency contracts | Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	3.6	4.3
Foreign currency contracts | Level 2 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	(0.2)	(0.1)
Derivatives - 2017 Interest Rate swap | Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	0.9	0.0
Derivatives - 2018 Interest Rate swap | Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	(0.4)	7.7
Commodity contract | Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - Foreign Currency contracts	0.2	0.0
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Fair Value Amount	$ 2,470.4	$ 599.2