Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Condensed Consolidating Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements Captions [Line Items]
Net sales	$ 4,423.7	$ 4,327.4
Cost of goods sold	3,614.7	3,545.6
Selling, general and administrative, excluding intangible amortization	425.7	400.9
Selling, general and administrative intangible amortization	101.8	92.9
Gain on disposal of assets	(1.3)	(43.8)
Restructuring and other costs	30.1	54.4
Operating profit (loss)	252.7	277.4
Interest (expense) income, net	(93.5)	(94.4)
Loss on extinguishment of debt		(1.9)
Pension and other postretirement non- service (expense) income	26.7	17.3
Other income (expense), net	(3.7)	(2.7)
Equity in income of unconsolidated entities	3.8	6.8
Income before income taxes	186.0	202.5
Income tax benefit (expense)	(46.5)	(62.7)
Consolidated net income	139.5	139.8
Less: Net income attributable to noncontrolling interests	(1.0)	(0.7)
Net income attributable to common stockholders	138.5	139.1
Comprehensive (loss) income attributable to common stockholders	246.2	79.6
Parent [Member]
Condensed Income Statements Captions [Line Items]
Equity in income of consolidated entities	138.5	139.1
Income before income taxes	138.5	139.1
Consolidated net income	138.5	139.1
Net income attributable to common stockholders	138.5	139.1
Comprehensive (loss) income attributable to common stockholders	246.2	79.6
Issuer [Member]
Condensed Income Statements Captions [Line Items]
Selling, general and administrative, excluding intangible amortization	0.2	0.1
Restructuring and other costs	1.6
Operating profit (loss)	(1.8)	(0.1)
Interest (expense) income, net	(64.7)	(47.0)
Intercompany interest income (expense), net	(3.5)	3.0
Loss on extinguishment of debt		(1.8)
Other income (expense), net		(0.6)
Equity in income of consolidated entities	226.6	198.7
Income before income taxes	156.6	152.2
Income tax benefit (expense)	17.5	11.1
Consolidated net income	174.1	163.3
Net income attributable to common stockholders	174.1	163.3
Comprehensive (loss) income attributable to common stockholders	283.6	106.5
Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales	589.3	623.8
Cost of goods sold	481.6	500.9
Selling, general and administrative, excluding intangible amortization	28.8	13.1
Selling, general and administrative intangible amortization	26.0	26.1
Gain on disposal of assets	(0.1)
Operating profit (loss)	53.0	83.7
Interest (expense) income, net	(35.2)	(49.9)
Intercompany interest income (expense), net	(25.2)	(27.1)
Pension and other postretirement non- service (expense) income	(1.9)	(1.7)
Other income (expense), net	1.1	0.6
Equity in income of consolidated entities	138.3	246.2
Income before income taxes	130.1	251.8
Income tax benefit (expense)	2.3	(1.9)
Consolidated net income	132.4	249.9
Net income attributable to common stockholders	132.4	249.9
Comprehensive (loss) income attributable to common stockholders	236.3	195.2
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales	4,460.5	4,333.8
Cost of goods sold	3,751.2	3,674.9
Selling, general and administrative, excluding intangible amortization	396.7	387.7
Selling, general and administrative intangible amortization	75.8	66.8
Gain on disposal of assets	(1.2)	(43.8)
Restructuring and other costs	28.5	54.4
Operating profit (loss)	209.5	193.8
Interest (expense) income, net	6.4	2.5
Intercompany interest income (expense), net	20.7	24.1
Loss on extinguishment of debt		(0.1)
Pension and other postretirement non- service (expense) income	28.6	19.0
Other income (expense), net	(4.8)	(2.7)
Equity in income of unconsolidated entities	3.8	6.8
Income before income taxes	264.2	243.4
Income tax benefit (expense)	(66.3)	(71.9)
Consolidated net income	197.9	171.5
Less: Net income attributable to noncontrolling interests	(1.0)	(0.7)
Net income attributable to common stockholders	196.9	170.8
Comprehensive (loss) income attributable to common stockholders	306.2	111.6
Eliminations [Member]
Condensed Income Statements Captions [Line Items]
Net sales	(626.1)	(630.2)
Cost of goods sold	(618.1)	(630.2)
Operating profit (loss)	(8.0)
Intercompany interest income (expense), net	8.0
Equity in income of consolidated entities	(503.4)	(584.0)
Income before income taxes	(503.4)	(584.0)
Consolidated net income	(503.4)	(584.0)
Net income attributable to common stockholders	(503.4)	(584.0)
Comprehensive (loss) income attributable to common stockholders	$ (826.1)	$ (413.3)