CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 4,620.0	$ 4,017.0		$ 8,947.4	$ 7,911.0
Cost of goods sold	3,720.4	3,227.6		7,266.0	6,348.1
Selling, general and administrative, excluding intangible amortization	444.1	395.8		845.0	776.6
Selling, general and administrative intangible amortization	102.4	75.2		195.3	147.7
Loss (gain) on disposal of assets		2.8		(43.8)	3.9
Multiemployer pension withdrawals					180.0
Land and Development impairments	13.0		$ 27.6	13.0	27.6
Restructuring and other costs	34.8	31.7		89.2	48.0
Operating profit (loss)	305.3	283.9		582.7	379.1
Interest expense, net	(111.8)	(78.3)		(206.2)	(143.1)
Gain (loss) on extinguishment of debt	0.4	0.1		(1.5)	(0.9)
Pension and other postretirement non-service income	18.7	24.6		36.0	49.2
Other (expense) income, net	(3.3)	1.1		(6.0)	3.6
Equity in (loss) income of unconsolidated entities	(0.2)	11.9		6.6	15.7
Income before income taxes	209.1	243.3		411.6	303.6
Income tax (expense) benefit	(47.2)	(18.8)		(109.9)	1,054.4
Consolidated net income	161.9	224.5		301.7	1,358.0
Less: Net (income) loss attributable to noncontrolling interests	(1.5)	(1.3)		(2.2)	0.3
Net income attributable to common stockholders	$ 160.4	$ 223.2		$ 299.5	$ 1,358.3
Basic earnings per share attributable to common stockholders	$ 0.63	$ 0.87		$ 1.17	$ 5.32
Diluted earnings per share attributable to common stockholders	$ 0.62	$ 0.86		$ 1.15	$ 5.23
Basic weighted average shares outstanding	256.6	256.1		255.7	255.5
Diluted weighted average shares outstanding	259.4	260.3		259.4	259.7
Cash dividends paid per common share	$ 0.455	$ 0.43		$ 0.91	$ 0.86