Shareowners' Equity - Schedule of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ 3,016.7	$ 2,694.1	$ 1,346.8
Other comprehensive income	127.5	99.3	596.4
End of period	3,743.4	3,016.7	2,694.1
Total accumulated other comprehensive loss, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(917.5)	(1,017.1)	(1,614.2)
Other comprehensive income (loss) before reclassifications	63.2	37.0	441.1
Amounts reclassified from accumulated other comprehensive loss	64.2	62.6	156.0
Other comprehensive income	127.4	99.6	597.1
End of period	(790.1)	(917.5)	(1,017.1)
Pension and other postretirement benefit plan adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(447.8)	(694.1)	(1,271.2)
Other comprehensive income (loss) before reclassifications	(49.7)	170.7	438.9
Amounts reclassified from accumulated other comprehensive loss	90.4	75.6	138.2
Other comprehensive income	40.7	246.3	577.1
End of period	(407.1)	(447.8)	(694.1)
Accumulated currency translation adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(465.0)	(280.1)	(311.5)
Other comprehensive income (loss) before reclassifications	100.1	(184.9)	31.4
Other comprehensive income	100.1	(184.9)	31.4
End of period	(364.9)	(465.0)	(280.1)
Accumulated gain (loss), net, cash flow hedge, parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(4.7)	(42.9)	(31.5)
Other comprehensive income (loss) before reclassifications	12.8	51.2	(29.2)
Amounts reclassified from accumulated other comprehensive loss	(26.2)	(13.0)	17.8
Other comprehensive income	(13.4)	38.2	(11.4)
End of period	$ (18.1)	$ (4.7)	$ (42.9)