Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Deferred income tax assets:
Compensation and benefits	$ 6.5	$ 18.8
Inventory	11.5	20.2
Returns, rebates and incentives	34.0	45.9
Retirement benefits	141.5	305.5
Environmental remediation and other site-related costs	20.7	33.4
Share-based compensation	19.6	32.4
Other accruals and reserves	49.7	71.3
Net operating loss carryforwards	19.6	20.4
Tax credit carryforwards	17.9	15.3
Capital loss carryforwards	10.0	10.3
Other	4.6	11.1
Subtotal	335.6	584.6
Valuation allowance	(27.0)	(18.6)
Net deferred income tax assets	308.6	566.0
Deferred income tax liabilities:
Property	(54.7)	(74.0)
Intangible assets	(25.3)	(45.9)
Investments	(21.7)	0.0
Unremitted earnings of foreign subsidiaries	(22.7)	0.0
Other	(4.6)	(2.5)
Deferred income tax liabilities	(129.0)	(122.4)
Total net deferred income tax assets	$ 179.6	$ 443.6