Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Condensed Consolidating Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Condensed Income Statements Captions [Line Items]
Net sales	$ 4,447.3	$ 4,620.0	$ 8,871.0	$ 8,947.4
Cost of goods sold	3,642.5	3,720.4	7,257.2	7,266.0
Gross profit	804.8	899.6	1,613.8	1,681.4
Selling, general and administrative, excluding intangible amortization	418.6	444.1	844.3	845.0
Selling, general and administrative intangible amortization	100.1	102.4	201.9	195.3
Loss (gain) on disposal of assets	(5.6)		(6.9)	(43.8)
Multiemployer pension withdrawal expense	0.9		0.9
Land and Development impairments		13.0		13.0
Restructuring and other costs	16.4	34.8	46.5	89.2
Operating profit (loss)	274.4	305.3	527.1	582.7
Interest (expense) income, net	(97.3)	(111.8)	(190.8)	(206.2)
(Loss) gain on extinguishment of debt	(0.5)	0.4	(0.5)	(1.5)
Pension and other postretirement non- service (expense) income	26.1	18.7	52.8	36.0
Other income (expense), net	(0.9)	(3.3)	(4.6)	(6.0)
Equity in income (loss) of unconsolidated entities	4.9	(0.2)	8.7	6.6
Income before income taxes	206.7	209.1	392.7	411.6
Income tax benefit (expense)	(57.8)	(47.2)	(104.3)	(109.9)
Consolidated net income	148.9	161.9	288.4	301.7
Less: Net income attributable to noncontrolling interests	(0.8)	(1.5)	(1.8)	(2.2)
Net income attributable to common stockholders	148.1	160.4	286.6	299.5
Comprehensive income (loss) attributable to common stockholders	(236.0)	189.7	10.2	269.3
Parent [Member]
Condensed Income Statements Captions [Line Items]
Other income (expense), net	0.1		0.1
Equity in income of consolidated entities	148.0	160.4	286.5	299.5
Income before income taxes	148.1	160.4	286.6	299.5
Consolidated net income	148.1	160.4	286.6	299.5
Net income attributable to common stockholders	148.1	160.4	286.6	299.5
Comprehensive income (loss) attributable to common stockholders	(236.0)	189.7	10.2	269.3
Issuer [Member]
Condensed Income Statements Captions [Line Items]
Selling, general and administrative, excluding intangible amortization	0.1	0.3	0.3	0.4
Restructuring and other costs	2.0	3.9	3.6	3.9
Operating profit (loss)	(2.1)	(4.2)	(3.9)	(4.3)
Interest (expense) income, net	(63.8)	(65.0)	(128.5)	(112.0)
Intercompany interest income (expense), net	(3.3)	0.5	(6.8)	3.5
(Loss) gain on extinguishment of debt	(0.4)		(0.4)	(1.8)
Other income (expense), net		(3.4)		(4.0)
Equity in income of consolidated entities	252.3	195.5	478.9	394.2
Income before income taxes	182.7	123.4	339.3	275.6
Income tax benefit (expense)	17.3	17.9	34.8	29.0
Consolidated net income	200.0	141.3	374.1	304.6
Net income attributable to common stockholders	200.0	141.3	374.1	304.6
Comprehensive income (loss) attributable to common stockholders	(184.9)	170.4	98.7	276.9
Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales	630.9	639.2	1,220.2	1,263.0
Cost of goods sold	502.2	526.8	983.8	1,027.7
Gross profit	128.7	112.4	236.4	235.3
Selling, general and administrative, excluding intangible amortization	27.9	14.2	56.7	27.3
Selling, general and administrative intangible amortization	24.5	26.2	50.5	52.3
Loss (gain) on disposal of assets	0.1
Multiemployer pension withdrawal expense	0.1		0.1
Restructuring and other costs		0.1		0.1
Operating profit (loss)	76.1	71.9	129.1	155.6
Interest (expense) income, net	(33.6)	(42.0)	(68.8)	(91.9)
Intercompany interest income (expense), net	(24.2)	(27.5)	(49.4)	(54.6)
(Loss) gain on extinguishment of debt		0.4		0.4
Pension and other postretirement non- service (expense) income	(1.9)	(1.7)	(3.8)	(3.4)
Other income (expense), net	0.2	(1.0)	1.3	(0.4)
Equity in income of consolidated entities	111.1	168.2	249.4	414.4
Income before income taxes	127.7	168.3	257.8	420.1
Income tax benefit (expense)	(4.0)	0.6	(1.7)	(1.3)
Consolidated net income	123.7	168.9	256.1	418.8
Net income attributable to common stockholders	123.7	168.9	256.1	418.8
Comprehensive income (loss) attributable to common stockholders	(247.9)	200.0	(11.6)	395.2
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales	4,479.1	4,638.1	8,939.6	8,971.9
Cost of goods sold	3,794.8	3,850.9	7,546.0	7,525.8
Gross profit	684.3	787.2	1,393.6	1,446.1
Selling, general and administrative, excluding intangible amortization	390.6	429.6	787.3	817.3
Selling, general and administrative intangible amortization	75.6	76.2	151.4	143.0
Loss (gain) on disposal of assets	(5.7)		(6.9)	(43.8)
Multiemployer pension withdrawal expense	0.8		0.8
Land and Development impairments		13.0		13.0
Restructuring and other costs	14.4	30.8	42.9	85.2
Operating profit (loss)	208.6	237.6	418.1	431.4
Interest (expense) income, net	0.1	(4.8)	6.5	(2.3)
Intercompany interest income (expense), net	19.3	27.0	40.0	51.1
(Loss) gain on extinguishment of debt	(0.1)		(0.1)	(0.1)
Pension and other postretirement non- service (expense) income	28.0	20.4	56.6	39.4
Other income (expense), net	(1.2)	1.1	(6.0)	(1.6)
Equity in income (loss) of unconsolidated entities	4.9	(0.2)	8.7	6.6
Income before income taxes	259.6	281.1	523.8	524.5
Income tax benefit (expense)	(71.1)	(65.7)	(137.4)	(137.6)
Consolidated net income	188.5	215.4	386.4	386.9
Less: Net income attributable to noncontrolling interests	(0.8)	(1.5)	(1.8)	(2.2)
Net income attributable to common stockholders	187.7	213.9	384.6	384.7
Comprehensive income (loss) attributable to common stockholders	(190.1)	243.6	116.1	355.2
Eliminations [Member]
Condensed Income Statements Captions [Line Items]
Net sales	(662.7)	(657.3)	(1,288.8)	(1,287.5)
Cost of goods sold	(654.5)	(657.3)	(1,272.6)	(1,287.5)
Gross profit	(8.2)		(16.2)
Operating profit (loss)	(8.2)		(16.2)
Intercompany interest income (expense), net	8.2		16.2
Equity in income of consolidated entities	(511.4)	(524.1)	(1,014.8)	(1,108.1)
Income before income taxes	(511.4)	(524.1)	(1,014.8)	(1,108.1)
Consolidated net income	(511.4)	(524.1)	(1,014.8)	(1,108.1)
Net income attributable to common stockholders	(511.4)	(524.1)	(1,014.8)	(1,108.1)
Comprehensive income (loss) attributable to common stockholders	$ 622.9	$ (614.0)	$ (203.2)	$ (1,027.3)