Shareowners' Equity - Schedule of Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense)	$ (5.7)	$ 29.7	$ (6.1)
Sales	6,997.4	6,329.8	6,694.8
Cost of sales	(4,099.7)	(3,734.6)	(3,794.7)
Selling, general and administrative expenses	(1,680.0)	(1,479.8)	(1,538.5)
Interest expense	(94.6)	(103.5)	(98.2)
Income before income taxes	1,526.2	1,136.1	901.0
Income tax provision	(181.9)	(112.9)	(205.2)
Net income	1,358.1	1,023.4	695.8
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	156.0	98.3	44.4
Amortization of prior service credit | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense)	(4.0)	(4.5)	(4.2)
Amortization of net actuarial loss | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense)	142.5	148.7	78.7
Settlements | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense)	39.8	0.0	1.2
Pension and other postretirement benefit plan adjustments, net of tax | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	178.3	144.2	75.7
Income tax provision	(40.1)	(34.7)	(19.2)
Net income	138.2	109.5	56.5
Accumulated gain (loss), net, cash flow hedge, parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	(1.9)	0.7	(1.0)
Cost of sales	25.4	(19.6)	(18.2)
Selling, general and administrative expenses	(1.5)	1.4	1.3
Interest expense	2.3	2.1	1.2
Income before income taxes	24.3	(15.4)	(16.7)
Income tax provision	(6.5)	4.2	4.6
Net income	$ 17.8	$ (11.2)	$ (12.1)