Shareowners' Equity - Schedule of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ 2,694.1	$ 1,346.8	$ 404.2
Other comprehensive income	99.3	596.4	16.5
End of period	3,016.7	2,694.1	1,346.8
Total accumulated other comprehensive loss, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(1,017.1)	(1,614.2)	(1,488.0)
Other comprehensive (loss) income before reclassifications	37.0	441.1	(81.5)
Amounts reclassified from accumulated other comprehensive loss	62.6	156.0	98.3
Other comprehensive income	99.6	597.1	16.8
End of period	(917.5)	(1,017.1)	(1,614.2)
Pension and other postretirement benefit plan adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(694.1)	(1,271.2)	(1,133.7)
Other comprehensive (loss) income before reclassifications	170.7	438.9	(100.2)
Amounts reclassified from accumulated other comprehensive loss	75.6	138.2	109.5
Other comprehensive income	246.3	577.1	9.3
End of period	(447.8)	(694.1)	(1,271.2)
Accumulated currency translation adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(280.1)	(311.5)	(341.3)
Other comprehensive (loss) income before reclassifications	(184.9)	31.4	26.0
Other comprehensive income	(184.9)	31.4	26.0
End of period	(465.0)	(280.1)	(311.5)
Accumulated gain (loss), net, cash flow hedge, parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(42.9)	(31.5)	(13.0)
Other comprehensive (loss) income before reclassifications	51.2	(29.2)	(7.3)
Amounts reclassified from accumulated other comprehensive loss	(13.0)	17.8	(11.2)
Other comprehensive income	38.2	(11.4)	(18.5)
End of period	$ (4.7)	$ (42.9)	(31.5)
Adoption of accounting standard/other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period			2.2
Adoption of accounting standard/other | Total accumulated other comprehensive loss, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period			(146.8)
Adoption of accounting standard/other | Pension and other postretirement benefit plan adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period			(146.8)
Adoption of accounting standard/other | Accumulated currency translation adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period			3.8
Adoption of accounting standard/other | Total accumulated other comprehensive loss, including non-controlling interest, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period			$ (143.0)