Accumulated Other Comprehensive Loss - Reclassifications out of Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 299.6	$ 230.3	$ 597.4	$ 487.9
Income tax provision	(72.2)	(40.8)	(606.4)	(83.7)
Sales	(1,651.2)	(1,554.3)	(3,237.8)	(3,044.6)
Cost of sales	(950.4)	(897.8)	(1,839.9)	(1,745.8)
Selling, general and administrative expenses	(389.2)	(409.2)	(778.5)	(779.2)
Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	25.2	22.5	49.3	46.1
Pension and other postretirement benefit plan adjustments [Member] \| Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	27.6	36.2	55.2	72.6
Income tax provision	(7.4)	(12.4)	(14.8)	(25.0)
Net income	20.2	23.8	40.4	47.6
Amortization Of Prior Service Credit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(1.3)	(2.6)	(2.4)	(4.9)
Amortization Of Net Actuarial Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	28.9	38.8	57.6	77.3
Settlements [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0.0	0.0	0.0	0.2
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] \| Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	6.8	(1.3)	12.0	(1.5)
Income tax provision	(1.8)	0.0	(3.1)	0.0
Net income	5.0	(1.3)	8.9	(1.5)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] \| Foreign Exchange Contracts [Member] \| Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	0.8	(1.0)	1.3	(1.5)
Cost of sales	8.4	(2.6)	14.3	(3.6)
Selling, general and administrative expenses	$ (0.8)	$ 0.3	$ (1.0)	$ 0.6

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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