CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions		Total		Common Stock [Member]		Capital in Excess of Par Value [Member]		Retained Earnings [Member]	AOCI Attributable to Parent	Noncontrolling Interests [Member]
Beginning balance at Sep. 30, 2017				254,500,000
Shares issued under restricted stock plan				700,000
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			1,200,000
Purchases of common stock		0
Ending balance at Mar. 31, 2018				256,400,000
Beginning balance at Sep. 30, 2017				$ 2.5		$ 10,624.9		$ 172.4	$ (457.3)	$ 43.6	[2]
Net income (loss)		$ 0.3
Distributions and adjustments to noncontrolling interests	[2]									(9.3)
Net income attributable to common stockholders								1,358.3
Dividends declared (per share - $0.455, $0.43, $0.91 and $0.86)	[3]							(221.9)
Compensation expense under share-based plans						33.7
Issuance of common stock, net of stock received for minimum tax withholdings				0.1	[1]	26.0	[1]	(6.4)
Other comprehensive loss, net of tax		15.6	[4]						15.6
Ending balance at Mar. 31, 2018		11,582.2		$ 2.6		10,684.6		1,302.4	(441.7)	34.3	[2]
Total Stockholders’ equity at Mar. 31, 2018		11,547.9
Beginning balance at Dec. 31, 2017				254,900,000
Shares issued under restricted stock plan				700,000
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			800,000
Ending balance at Mar. 31, 2018				256,400,000
Beginning balance at Dec. 31, 2017				$ 2.5		10,651.7		1,196.8	(497.6)	40.2	[2]
Net income (loss)		(1.3)								1.1	[2]
Distributions and adjustments to noncontrolling interests	[2]									(7.0)
Net income attributable to common stockholders								223.2
Dividends declared (per share - $0.455, $0.43, $0.91 and $0.86)	[3]							(111.2)
Compensation expense under share-based plans						19.4
Issuance of common stock, net of stock received for minimum tax withholdings				0.1	[1]	13.5	[1]	(6.4)
Other comprehensive loss, net of tax									55.9
Ending balance at Mar. 31, 2018		11,582.2		$ 2.6		10,684.6		1,302.4	(441.7)	34.3	[2]
Total Stockholders’ equity at Mar. 31, 2018		$ 11,547.9
Beginning balance at Sep. 30, 2018		253,500,000		253,500,000
Shares issued under restricted stock plan				3,000,000
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			2,500,000
Purchases of common stock		(2,100,000)		(2,100,000)
Ending balance at Mar. 31, 2019		256,900,000		256,900,000
Beginning balance at Sep. 30, 2018		$ 11,482.4		$ 2.5		10,588.9		1,573.3	(695.3)	13.0	[2]
Net income (loss)		(2.2)								1.4	[2]
Contributions	[2]									0.2
Distributions and adjustments to noncontrolling interests	[2]									(1.8)
Adoption of revenue from contracts with customers standard								43.5
Net income attributable to common stockholders								299.5
Dividends declared (per share - $0.455, $0.43, $0.91 and $0.86)	[3]							(242.3)
Compensation expense under share-based plans						36.1
Issuance of common stock, net of stock received for minimum tax withholdings				0.1	[1]	82.9	[1]	(0.4)
Fair value of share-based awards issued in business combinations						70.8
Other comprehensive loss, net of tax		(30.2)	[4]						(30.2)
Purchases of common stock						(86.2)		(2.4)
Ending balance at Mar. 31, 2019		11,653.6		$ 2.6		10,692.5		1,671.2	(725.5)	12.8	[2]
Total Stockholders’ equity at Mar. 31, 2019		$ 11,640.8
Beginning balance at Dec. 31, 2018				255,200,000
Shares issued under restricted stock plan				2,700,000
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			100,000
Purchases of common stock				(1,100,000)
Ending balance at Mar. 31, 2019		256,900,000		256,900,000
Beginning balance at Dec. 31, 2018				$ 2.6		10,720.6		1,635.3	(754.8)	11.8	[2]
Net income (loss)		$ (1.5)								1.1	[2]
Distributions and adjustments to noncontrolling interests	[2]									(0.1)
Net income attributable to common stockholders								160.4
Dividends declared (per share - $0.455, $0.43, $0.91 and $0.86)	[3]							(124.5)
Compensation expense under share-based plans						18.2
Issuance of common stock, net of stock received for minimum tax withholdings	[1]					(1.9)
Other comprehensive loss, net of tax									29.3
Purchases of common stock						(44.4)
Ending balance at Mar. 31, 2019		11,653.6		$ 2.6		$ 10,692.5		$ 1,671.2	$ (725.5)	$ 12.8	[2]
Total Stockholders’ equity at Mar. 31, 2019		$ 11,640.8

[1] Included in the issuance of common stock in the six months ended March 31, 2019 is the issuance of approximately 1.6 million shares of Common Stock (as hereinafter defined) valued at $70.1 million in connection with the KapStone Acquisition (as hereinafter defined).

[2] Excludes amounts related to contingently redeemable noncontrolling interests, which are separately classified outside of permanent equity on the Condensed Consolidated Balance Sheets.

[3] Includes cash dividends paid, dividend equivalent units on certain restricted stock awards and dividends declared but unpaid related to the shares reserved but unissued at the time of the acquisition for the resolution of Smurfit-Stone Container Corporation (“Smurfit-Stone”) bankruptcy claims.

[4] All amounts are net of tax and noncontrolling interests.