Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Gross Deferred Tax Assets
Retirement benefits and compensation accruals	$ 75.2	$ 77.2
Tax loss carryforwards	141.8	126.3
Tax credits and other tax carryforwards	46.2	39.2
Reserves and accruals	65.2	55.4
Other	81.3	68.3
Valuation allowance	(153.3)	(100.1)
Deferred Tax Assets	256.4	266.3
Gross Deferred Tax Liabilities
Plant and equipment	1,192.0	1,187.6
Currency gains	20.6	22.5
Unremitted earnings of foreign entities	72.0	72.9
Partnership and other investments	18.6	16.1
Intangible assets	48.5	69.8
Other	11.1	9.1
Deferred Tax Liabilities	1,362.8	1,378.0
Net Deferred Income Tax Liability	$ 1,106.4	$ 1,111.7