Shareowners' Equity - Schedule of Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	$ (1,729.5)	$ (1,698.7)	$ (1,651.2)	$ (1,586.6)	$ (1,667.5)	$ (1,599.2)	$ (1,554.3)	$ (1,490.3)	$ (6,666.0)	$ (6,311.3)	$ (5,879.5)
Cost of sales									(3,793.8)	(3,687.1)	(3,404.0)
Selling, general and administrative expenses									(1,599.0)	(1,591.5)	(1,467.4)
Income before income taxes									1,330.8	1,037.4	943.1
Income tax provision									(795.3)	(211.7)	(213.4)
Net income	$ 345.9	$ 198.6	$ 227.4	$ (236.4)	$ 204.6	$ 216.9	$ 189.5	$ 214.7	535.5	825.7	729.7
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income									90.6	99.6	58.4
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and selling, general and administrative expenses									(4.9)	(9.8)	(14.0)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and selling, general and administrative expenses									115.1	155.2	126.8
Accumulated Defined Benefit Plans Adjustment, Settlements Attributable To Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and selling, general and administrative expenses									0.7	2.8	0.0
Pension and other postretirement benefit plan adjustments, net of tax (Note 12) | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes									110.9	148.2	112.8
Income tax provision									(30.4)	(50.6)	(39.0)
Net income									80.5	97.6	73.8
Net unrealized gains (losses) on cash flow hedges, net of tax | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes									13.6	3.0	(19.1)
Income tax provision									(3.5)	(1.0)	3.7
Net income									10.1	2.0	(15.4)
Forward exchange contracts | Net unrealized gains (losses) on cash flow hedges, net of tax | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales									(2.4)	(0.3)	5.5
Cost of sales									17.2	2.8	(25.5)
Selling, general and administrative expenses									$ (1.2)	$ 0.5	$ 0.9