Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Gross Deferred Tax Assets
Retirement benefits and compensation accruals	$ 153.1	$ 370.1
Tax loss carryforwards	143.5	64.5
Tax credits and other tax carryforwards	17.1	76.1
Reserves and accruals	42.5	88.2
Currency losses	3.8	20.7
Other	45.4	37.2
Valuation allowance	(105.0)	(107.7)
Deferred Tax Assets	300.4	549.1
Gross Deferred Tax Liabilities
Plant and equipment	811.8	1,035.6
Unremitted earnings of foreign entities	36.1	20.9
Partnership and other investments	16.3	5.4
Intangible assets	84.3	81.9
Other	5.6	9.2
Deferred Tax Liabilities	954.1	1,153.0
Net Deferred Income Tax Liability	$ 653.7	$ 603.9