Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Deferred income tax assets:
Compensation and benefits	$ 6.0	$ 6.5
Inventory	11.1	11.5
Returns, rebates and incentives	29.8	34.0
Retirement benefits	298.5	141.5
Environmental remediation and other site-related costs	26.2	20.7
Share-based compensation	21.6	19.6
Other accruals and reserves	46.9	49.7
Investments	69.6	0.0
Net operating loss carryforwards	18.5	19.6
Tax credit carryforwards	16.5	17.9
Capital loss carryforwards	9.5	10.0
Other	10.7	4.6
Subtotal	564.9	335.6
Valuation allowance	(93.8)	(27.0)
Net deferred income tax assets	471.1	308.6
Deferred income tax liabilities:
Property	(55.8)	(54.7)
Intangible assets	(24.4)	(25.3)
Investments	0.0	(21.7)
Unremitted earnings of foreign subsidiaries	(25.5)	(22.7)
Other	(1.3)	(4.6)
Deferred income tax liabilities	(107.0)	(129.0)
Total net deferred income tax assets	$ 364.1	$ 179.6