CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Net sales	$ 4,726.7	$ 5,277.6	$ 9,346.7	$ 10,200.7
Cost of goods sold	3,946.6	4,357.6	7,807.8	8,514.7
Gross profit	780.1	920.0	1,538.9	1,686.0
Selling, general and administrative expense excluding intangible amortization	499.5	498.9	1,026.6	978.0
Selling, general and administrative intangible amortization expense	79.0	86.2	161.0	172.8
Restructuring and other costs, net	81.2	435.8	146.7	467.9
Impairment of goodwill		1,893.0		1,893.0
Operating profit (loss)	120.4	(1,993.9)	204.6	(1,825.7)
Interest expense, net	(100.8)	(108.4)	(202.2)	(205.7)
Pension and other postretirement non-service cost	(0.6)	(6.0)	(0.4)	(11.0)
Other (expense) income, net	(13.5)	(17.8)	(18.2)	7.4
Equity in income (loss) of unconsolidated entities	2.9	4.5	7.1	(31.5)
Loss on sale of RTS and Chattanooga	(2.0)		(1.5)
Income (loss) before income taxes	6.4	(2,121.6)	(10.6)	(2,066.5)
Income tax expense	10.0	116.8	4.3	108.5
Consolidated net income (loss)	16.4	(2,004.8)	(6.3)	(1,958.0)
Less: Net income attributable to noncontrolling interests	(0.9)	(1.3)	(0.6)	(2.8)
Net income (loss) attributable to common stockholders	$ 15.5	$ (2,006.1)	$ (6.9)	$ (1,960.8)
Basic earnings (loss) per share attributable to common stockholders	$ 0.06	$ (7.85)	$ (0.03)	$ (7.68)
Diluted earnings (loss) per share attributable to common stockholders	$ 0.06	$ (7.85)	$ (0.03)	$ (7.68)
Basic weighted average shares outstanding	258.0	255.6	257.5	255.2
Diluted weighted average shares outstanding	259.3	255.6	257.5	255.2