Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Gross Deferred Tax Assets
Retirement benefits and compensation accruals	$ 209.0	$ 227.1
Tax loss carryforwards	112.6	140.6
Tax credits and other tax carryforwards	40.3	31.1
Reserves and accruals	67.0	69.6
Currency losses	30.4	0.0
Other	64.6	57.7
Valuation allowance	(95.0)	(92.1)
Deferred Tax Assets	428.9	434.0
Gross Deferred Tax Liabilities
Plant and equipment	1,110.9	954.6
Currency gains	0.0	23.9
Unremitted earnings of foreign entities	58.7	31.0
Partnership and other investments	19.3	14.8
Intangible assets	83.6	80.0
Other	3.9	8.3
Deferred Tax Liabilities	1,276.4	1,112.6
Net Deferred Income Tax Liability	$ 847.5	$ 678.6