Income Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Gross Deferred Tax Assets
Retirement benefits and compensation accruals	$ 370.1	$ 527.6
Tax loss carryforwards	64.5	101.1
Tax credits and other tax carryforwards	76.1	56.0
Reserves and accruals	88.2	74.9
Partnership and other investments	0.0	5.8
Currency losses	20.7	0.0
Other	37.2	19.3
Valuation allowance	(107.7)	(165.1)
Deferred Tax Assets	549.1	619.6
Gross Deferred Tax Liabilities
Plant and equipment	1,035.6	985.1
Currency gains	0.0	46.8
Unremitted earnings of foreign entities	20.9	5.4
Partnership and other investments	5.4	0.0
Intangible assets	81.9	91.0
Other	9.2	16.7
Deferred Tax Liabilities	1,153.0	1,145.0
Deferred Tax Liabilities	$ 603.9	$ 525.4