WestRock (WRK) 10-K 16 Nov 18 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Nov. 01, 2018	Mar. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	WRK
Entity Registrant Name	WestRock CO
Entity Central Index Key	1,732,845
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		253,551,938
Entity Public Float			$ 16,230
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 16,285.1	$ 14,859.7	$ 14,171.8
Cost of goods sold	12,891.2	12,119.5	11,413.2
Selling, general and administrative, excluding intangible amortization	1,493.3	1,399.6	1,379.4
Selling, general and administrative intangible amortization	296.6	229.6	211.8
Multiemployer pension withdrawals	184.2
Pension risk transfer expense			370.7
Pension lump sum settlement		32.6
Land and Development impairments	31.9	46.7
Restructuring and other costs	105.4	196.7	366.4
Operating profit	1,282.5	835	430.3
Interest expense, net	(293.8)	(222.5)	(212.5)
(Loss) gain on extinguishment of debt	(0.1)	1.8	2.7
Other income, net	12.7	11.5	14.4
Equity in income of unconsolidated entities	33.5	39	9.7
Gain on sale of HH&B		192.8
Income from continuing operations before income taxes	1,034.8	857.6	244.6
Income tax benefit (expense)	874.5	(159)	(89.8)
Income from continuing operations	1,909.3	698.6	154.8
Loss from discontinued operations (net of income tax benefit of $0, $0 and $32.3)			(544.7)
Consolidated net income (loss)	1,909.3	698.6	(389.9)
Less: Net (income) loss attributable to noncontrolling interests	(3.2)	9.6	(6.4)
Net income (loss) attributable to common stockholders	$ 1,906.1	$ 708.2	$ (396.3)
Basic earnings per share from continuing operations	$ 7.46	$ 2.81	$ 0.60
Basic loss per share from discontinued operations			(2.16)
Basic earnings (loss) per share attributable to common stockholders	7.46	2.81	(1.56)
Diluted earnings per share from continuing operations	7.34	2.77	0.59
Diluted loss per share from discontinued operations			(2.13)
Diluted earnings (loss) per share attributable to common stockholders	7.34	2.77	(1.54)
Cash dividends paid per share	$ 1.72	$ 1.60	$ 1.50

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Discontinued Operation, Tax Effect of Discontinued Operation	$ 0	$ 0	$ 32.3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income (loss)	$ 1,909.3	$ 698.6	$ (389.9)
Other comprehensive (loss) income, net of tax:
Foreign currency translation (loss) gain	(234.4)	80.7	109.8
Reclassification adjustment of net loss on foreign currency translation included in earnings	0	0	20.2
Sale of HH&B	0	26.8	0
Derivatives:
Deferred loss on cash flow hedges	0	0	(0.4)
Reclassification adjustment of net loss (gain) on cash flow hedges included in earnings	0.5	(0.5)	1.2
Unrealized gain on available for sale security	0.8	0.7	0
Reclassification adjustment of gain on available for sale security included in earnings	(1.5)	0	0
Defined benefit pension and other postretirement benefit plans:
Net actuarial (loss) gain arising during period	(13.1)	22.2	(224.6)
Amortization and settlement recognition of net actuarial loss, included in pension and postretirement cost	15	36	236.5	[1]
Prior service (cost) credit arising during period	(5.5)	0.7	1.4
Amortization and curtailment recognition of prior service cost (credit), included in pension and postretirement cost	0.2	(0.2)	1.1
Sale of HH&B	0	2.9	0
Other comprehensive (loss) income, net of tax	(238)	169.3	145.2
Comprehensive income (loss)	1,671.3	867.9	(244.7)
Less: Comprehensive (income) loss attributable to noncontrolling interests	(3.2)	9.4	(5.7)
Comprehensive income (loss) attributable to common stockholders	$ 1,668.1	$ 877.3	$ (250.4)
[1]	Includes pension risk transfer expense.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Sep. 30, 2018	Sep. 30, 2017
Current Assets:
Cash and cash equivalents		$ 636.8	$ 298.1
Restricted cash		0	5.9
Accounts receivable (net of allowances of $49.7 and $45.8)		2,010.7	1,886.8
Inventories		1,829.6	1,797.3
Other current assets		248.5	329.2
Assets held for sale		59.5	173.6
Total current assets		4,785.1	4,490.9
Property, plant and equipment, net		9,082.5	9,118.3
Goodwill		5,577.6	5,528.3
Intangibles, net		3,122	3,329.3
Restricted assets held by special purpose entities		1,281	1,287.4
Prepaid pension asset		420	368
Other assets		1,092.3	966.8
Total Assets		25,360.5	25,089
Current liabilities:
Current portion of debt		740.7	608.7
Accounts payable		1,716.8	1,492.1
Accrued compensation and benefits		399.3	416.7
Other current liabilities		476.5	492.3
Total current liabilities		3,333.3	3,009.8
Long-term debt due after one year		5,674.5	5,946.1
Pension liabilities, net of current portion		261.3	279.4
Postretirement benefit liabilities, net of current portion		134.8	153.4
Non-recourse liabilities held by special purpose entities		1,153.7	1,161.9
Deferred income taxes		2,321.5	3,410.2
Other long-term liabilities		994.8	737.4
Commitments and contingencies (Notes 14 and 17)
Redeemable noncontrolling interests		4.2	4.7
Equity:
Preferred stock, $0.01 par value; 30.0 million shares authorized; no shares outstanding		0	0
Common stock, $0.01 par value; 600.0 million shares authorized; 253.5 million and 254.5 million shares outstanding at September 30, 2018 and September 30, 2017, respectively		2.5	2.5
Capital in excess of par value		10,588.9	10,624.9
Retained earnings		1,573.3	172.4
Accumulated other comprehensive loss	[1]	(695.3)	(457.3)
Total stockholders’ equity		11,469.4	10,342.5
Noncontrolling interests		13	43.6
Total equity		11,482.4	10,386.1
Total Liabilities and Equity		$ 25,360.5	$ 25,089
[1]	All amounts are net of tax and noncontrolling interest

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Statement Of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 49.7	$ 45.8
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	30,000,000	30,000,000
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	600,000,000	600,000,000
Common Stock, Shares, Outstanding	253,500,000	254,500,000

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Millions, $ 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, 2015				257
Shares issued under restricted stock plan				1.6
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			0.5
Purchases of common stock		(8.1)		(8.1)	[2]
Ending balance at Sep. 30, 2016				251
Beginning balance at Sep. 30, 2015				$ 2.6		$ 10,767.8		$ 1,661.6	$ (780.2)	$ 132.1	[3]
Noncontrolling interests assumed in business combinations	[3]									10.9
Net income (loss)		$ (6.4)								3.2	[3]
Distributions and adjustments to noncontrolling interests										(18.7)
Sale of subsidiary shares from noncontrolling interest	[3]									(0.2)
Net income (loss) attributable to common stockholders								(396.3)
Dividends declared (per share - $1.72, $1.60 and $1.50)	[4]							(384.2)
Income tax benefit (expense) from share-based plans						(15.5)
Compensation expense under share-based plans						76
Issuance of common stock, net of stock received for minimum tax withholdings						13.9		(0.8)
Purchases of common stock		(335.3)		(0.1)	[2]	(319.2)	[2]	(16)
Other comprehensive income (loss), net of tax		145.9							145.9
Separation of Specialty Chemicals business						(64.4)		(970.2)	7.9	(26.1)	[3]
Ending balance at Sep. 30, 2016		9,830		$ 2.5		10,458.6		(105.9)	(626.4)	101.2	[3]
Total Stockholders’ equity at Sep. 30, 2016		9,728.8
Other comprehensive income attributable to noncontrolling interest		$ 145.2
Shares issued under restricted stock plan				1.1
Issuance of common stock, net of stock received for minimum tax withholdings	[1],[5]			4.2
Purchases of common stock		(1.8)		(1.8)	[2]
Ending balance at Sep. 30, 2017		254.5		254.5
Net income (loss)		$ 9.6								(12.9)	[3]
Distributions and adjustments to noncontrolling interests										(44.7)
Net income (loss) attributable to common stockholders								708.2
Dividends declared (per share - $1.72, $1.60 and $1.50)	[4]							(407.3)
Income tax benefit (expense) from share-based plans						4.3
Compensation expense under share-based plans						60.6
Issuance of common stock, net of stock received for minimum tax withholdings						181.6	[5]	(5.9)
Fair value of share-based awards issued in business combinations						1.9
Purchases of common stock		(93)				(76.3)	[2]	(16.7)
Other comprehensive income (loss), net of tax		169.1	[6]						169.1
Separation of Specialty Chemicals business						(5.8)
Ending balance at Sep. 30, 2017		10,386.1		$ 2.5		10,624.9		172.4	(457.3)	43.6	[3]
Total Stockholders’ equity at Sep. 30, 2017		10,342.5
Other comprehensive income attributable to noncontrolling interest		$ 169.3
Shares issued under restricted stock plan				0.7
Issuance of common stock, net of stock received for minimum tax withholdings	[1]			1.7
Purchases of common stock		(3.4)		(3.4)	[2]
Ending balance at Sep. 30, 2018		253.5		253.5
Net income (loss)		$ (3.2)								2.1	[3]
Contributions	[3]									0.5
Distributions and adjustments to noncontrolling interests										(33.2)
Net income (loss) attributable to common stockholders								1,906.1
Dividends declared (per share - $1.72, $1.60 and $1.50)	[4]							(445.2)
Compensation expense under share-based plans						66.9
Issuance of common stock, net of stock received for minimum tax withholdings						38.9		(6.7)
Purchases of common stock		(195.1)				(141.8)	[2]	(53.3)
Other comprehensive income (loss), net of tax		(238)	[6]						(238)
Ending balance at Sep. 30, 2018		11,482.4		$ 2.5		$ 10,588.9		$ 1,573.3	$ (695.3)	$ 13	[3]
Total Stockholders’ equity at Sep. 30, 2018		11,469.4
Other comprehensive income attributable to noncontrolling interest		$ (238)
[1]	In connection with the Smurfit-Stone Acquisition, there were approximately 1.4 million shares reserved but unissued at the time of the acquisition for the resolution of Smurfit-Stone bankruptcy claims. At September 30, 2017, 0.2 million shares remain reserved and unissued. The remaining shares were issued in fiscal 2018 as the claim’s distribution process was completed.
[2]	In fiscal 2018, we repurchased approximately 3.4 million shares of our Common Stock for an aggregate cost of $195.1 million. In fiscal 2017, we repurchased approximately 1.8 million shares of our Common Stock for an aggregate cost of $93.0 million. In fiscal 2016, we repurchased approximately 8.1 million shares of our Common Stock for an aggregate cost of $335.3 million.
[3]	Excludes amounts related to contingently redeemable noncontrolling interests, which are separately classified outside of permanent equity in the Consolidated Balance Sheets.
[4]	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 bankruptcy claims.
[5]	Included in the issuance of common stock in fiscal 2017 is the issuance of approximately 2.4 million shares of Common Stock valued at $136.1 million in connection with the U.S. Corrugated Acquisition.
[6]	All amounts are net of tax and noncontrolling interest

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical Information) - USD ($) shares in Millions, $ in Millions	Jun. 09, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Cash dividends paid per share		$ 1.72	$ 1.60	$ 1.50
Purchases of common stock		3.4	1.8	8.1
Aggregate cost for purchase of common stock		$ 195.1	$ 93	$ 335.3
Common Stock [Member]
Purchases of common stock		3.4	1.8	8.1
U.S. Corrugated [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	2.4		2.4
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 136.1		$ 136.1
Smurfit Stone [Member]
Common Stock, Capital Shares Reserved for Future Issuance		0	0.2	0.3	1.4

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Consolidated net income (loss)	$ 1,909.3	$ 698.6	$ (389.9)
Adjustments to reconcile consolidated net income to net cash provided by operating activities:
Depreciation, depletion and amortization	1,252.2	1,112.1	1,141.9
Cost of real estate sold	121.2	207.9	87.7
Deferred income tax benefit	(1,069.4)	(20.4)	(160.9)
Share-based compensation expense	66.8	58	75.7
Pension and other postretirement funding (more) than expense (income)	(96.8)	(51)	275.6
Multiemployer pension withdrawals	184.2
Gain on sale of HH&B		(192.8)
Land and Development impairments	31.9	46.7
Other impairment adjustments	13.5	56.8	200.8
Impairment of Specialty Chemicals goodwill and intangibles			579.4
Other	(85.5)	(92.2)	(87.1)
Change in operating assets and liabilities, net of acquisitions and divestitures:
Accounts receivable	(143.4)	(97.9)	36.6
Inventories	(72.1)	(48.2)	50.6
Other assets	(22.6)	(33.7)	(92.7)
Accounts payable	180.3	302.2	(197.1)
Income taxes	130.6	(67.1)	73.2
Accrued liabilities and other	20.7	21.5	94.6
Net cash provided by operating activities	2,420.9	1,900.5	1,688.4
Investing activities:
Capital expenditures	(999.9)	(778.6)	(796.7)
Cash paid for purchase of businesses, net of cash acquired	(239.9)	(1,588.5)	(376.4)
Debt purchased in connection with an acquisition			(36.5)
Investment in unconsolidated entities	(114.3)	(2.5)	(179.9)
Proceeds from sale of HH&B		1,005.9
Proceeds from sale of property, plant and equipment	23.3	52.6	31.2
Other	31.9	25.3	6.9
Net cash used for investing activities	(1,298.9)	(1,285.8)	(1,351.4)
Financing activities:
Proceeds from issuance of notes	1,197.3	998.4
(Repayments) additions to revolving credit facilities	(115.5)	421.8	125.5
Additions to debt	855.2	742.6	1,511.8
Repayments of debt	(2,032.9)	(2,331.9)	(1,073.3)
Other financing (repayments) additions	(24.2)	23.9	53.3
Specialty Chemicals spin-off of net cash and trust funding			(105)
Issuances of common stock, net of related minimum tax withholdings	26.6	35.8	11.8
Purchases of common stock	(195.1)	(93)	(335.3)
Cash dividends paid to stockholders	(440.9)	(403.2)	(380.7)
Cash distributions paid to noncontrolling interests	(33.3)	(47)	(33.5)
Other	7.7	(2.8)	(5.6)
Net cash used for financing activities	(755.1)	(655.4)	(231)
Effect of exchange rate changes on cash and cash equivalents	(28.2)	(2.1)	6.6
Increase (decrease) in cash and cash equivalents	338.7	(42.8)	112.6
Cash and cash equivalents at beginning of period	298.1	340.9	228.3
Cash and cash equivalents at end of period	636.8	298.1	340.9
Supplemental disclosure of cash flow information:
Income taxes, net of refunds	60.5	227.6	157.4
Interest, net of amounts capitalized	$ 284.4	$ 239	$ 229.9

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018
Cash and cash equivalents from discontinued operations at beginning of period		$ 20.5
Equity Method Investments	$ 360.6	328.9	$ 457.8
Noncash, Accounts Receivable	14.6	34.7
Noncash, Inventories	7.6	25.8
Noncash, Other Assets	12.3	86.3
Noncash, Accounts Payable	(7.9)	(15.4)
Noncash, Income taxes	(1.4)	(1)
Noncash, Accrued Liabilities and Other	(12)	(18.8)
Investment in unconsolidated entities	(16.7)	(123.7)
Fair value of assets acquired, including goodwill	3,342.4	580.7	303.2
Cash consideration for the purchase of businesses, net of cash acquired	(1,592)	(376.4)	(242.1)
Stock issued in business combinations	(136.1)
Fair value of share-based awards issued in business combinations	(1.9)
Debt purchased in connection with an acquisition		(36.5)
Deferred payments and (unpaid) unreceived working capital or escrow	4.6	3.5	(25)
Liabilities and noncontrolling interest assumed	1,617	171.3	36.1
Debt assumed	$ 929.1	$ 15	$ 7.5

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Sep. 30, 2018
Description Of Business And Summary Of Significant Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	Note 1. Description of Business and Summary of Significant Accounting Policies Description of Business Unless the context otherwise requires, we , us , our , WestRock the Company WestRock is a multinational provider of paper and packaging solutions for consumer and corrugated packaging markets. We partner with our customers to provide differentiated paper and packaging solutions that help them win in the marketplace. Our team members support customers around the world from our operating and business locations in North America, South America, Europe, Asia and Australia. We also sell real estate primarily in the Charleston, SC region. WestRock was formed on March 6, 2015 for the purpose of effecting the Combination and, prior to the Combination, did not conduct any activities other than those incidental to its formation and the matters contemplated by the Business Combination Agreement. On July 1, 2015, pursuant to the Business Combination Agreement, RockTenn and MWV completed a strategic combination of their respective businesses and RockTenn and MWV each became wholly-owned subsidiaries of WestRock. RockTenn was the accounting acquirer in the Combination. See “ Note 2. Mergers, Acquisitions and Investment On May 15, 2016, WestRock completed the Separation, pursuant to which we disposed of our former Specialty Chemicals segment in its entirety and ceased to consolidate its assets, liabilities and results of operations in our consolidated financial statements. Accordingly, we have presented the financial position and results of operations of our former Specialty Chemicals segment as discontinued operations in the accompanying consolidated financial statements for all periods presented. See “ Note 7. Discontinued Operations During the second quarter of fiscal 2017, we committed to a plan to sell HH&B. On January 23, 2017, we announced we had entered into an agreement with certain subsidiaries of Silgan Holdings Inc. (“ Silgan On June 6, 2017, we completed the MPS Acquisition. MPS is a global provider of print-based specialty packaging solutions and its differentiated product offering includes premium folding cartons, inserts, labels and rigid packaging. MPS is reported in our Consumer Packaging segment. See “ Note 2. Mergers, Acquisitions and Investment Consolidation The consolidated financial statements include our accounts and the accounts of our partially-owned consolidated subsidiaries. Equity investments in which we exercise significant influence but do not control and are not the primary beneficiary are accounted for using the equity method. Investments in which we are not able to exercise significant influence over the investee are accounted for under the cost method. Our equity and cost method investments are not significant either individually or in the aggregate. We have eliminated all significant intercompany accounts and transactions. See “ Note 6. Segment Information Reclassifications During fiscal 2018, we presented our interest expense and interest income in a single line item, “interest expense, net”, in our consolidated statements of operations. The interest income was previously presented in the line item “interest income and other income (expense), net”, which is now presented as “other income, net”. The presentation of these two line items for fiscal 2017 and 2016 has been changed to conform to the current year presentation. In addition, we have excluded deferred financing costs from the line item depreciation, depletion and amortization on the consolidated statements of cash flows to conform with our current year presentation and have aggregated certain items into an “other’ caption in the operating, investing and financing activities sections of the consolidated statements of cash flows to conform with our current year presentation. Use of Estimates Preparing consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates, and the differences could be material. The most significant accounting estimates inherent in the preparation of our consolidated financial statements include estimates to evaluate the recoverability of goodwill, intangibles and property, plant and equipment, to determine the useful lives of assets that are amortized or depreciated, and to measure income taxes, self-insured obligations, restructuring activities and allocate the purchase price of an acquired business to the fair value of acquired assets and liabilities. In addition, significant estimates form the basis for our reserves with respect to collectability of accounts receivable, inventory valuations, pension benefits, deferred tax asset valuation allowances and certain benefits provided to current and retired employees. Various assumptions and other factors underlie the determination of these significant estimates. The process of determining significant estimates is fact specific and takes into account factors such as historical experience, current and expected economic conditions, product mix, and in some cases, actuarial techniques. We regularly evaluate these significant factors and make adjustments where facts and circumstances dictate. Revenue Recognition We recognize revenue when there is persuasive evidence that an arrangement exists, delivery has occurred or services have been rendered, our price to the buyer is fixed or determinable and collectability is reasonably assured. Delivery is not considered to have occurred until the customer takes title and assumes the risks and rewards of ownership. The timing of revenue recognition is dependent on the location of title transfer which is normally either on the exit from our plants (i.e., shipping point) or on arrival at customers’ plants (i.e., destination point). We do not recognize revenue from transactions where we bill customers, but retain custody and title to these products until the date custody and title transfer. We do not have any significant multiple deliverable revenue arrangements. We net, against our gross sales, provisions for discounts, returns, allowances, customer rebates and other adjustments. We account for such provisions during the same period in which we record the related revenues. We include in net sales any amounts related to shipping and handling that are billed to a customer. See “ Note 1. Description of Business and Summary of Significant Accounting Policies — New Accounting Standards — Recently Adopted ASU FASB ASC Revenue from Contracts with Customers Shipping and Handling Costs We classify shipping and handling costs, such as freight to our customers’ destinations, as a component of cost of goods sold. When shipping and handling costs are included in the sales price charged for our products, they are recognized in net sales. Cash Equivalents We consider all highly liquid investments that mature three months or less from the date of purchase to be cash equivalents. The carrying amounts we report in the consolidated balance sheets for cash and cash equivalents approximate fair market values. We place our cash and cash equivalents with large credit worthy banks, which limits the amount of our credit exposure. Accounts Receivable and Allowances We derive our accounts receivable from revenue earned from customers located primarily in North America, South America, Europe, Asia and Australia. Given our diverse customer base, we have limited exposure to credit loss from any particular customer or industry segment, and hence we generally do not require collateral. We perform an evaluation of probable credit losses inherent in our accounts receivable at each balance sheet date. Such an evaluation includes consideration of historical loss experience, trends in customer payment frequency, present economic conditions, and judgment about the future financial health of our customers and industry sector. The weighted average of our receivables collection is within 30 to 60 days. We sell certain receivables under our New A/R Sales Agreement. We state accounts receivable at the amount owed by the customer, net of an allowance for estimated uncollectible accounts, returns and allowances, cash discounts and other adjustments. We do not discount accounts receivable because we generally collect accounts receivable over a relatively short time. We account for sales and other taxes that are imposed on and concurrent with individual revenue-producing transactions between a customer and us on a net basis which excludes the taxes from our net sales. We charge off receivables when they are determined to be no longer collectible. In fiscal 2018, 2017 and 2016 our bad debt expense was not significant. The following table represents a summary of the changes in the reserve for allowance for doubtful accounts, returns and allowances and cash discounts for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 45.8 $ 36.5 $ 29.5 Reduction in sales and charges to costs and expenses 202.8 215.6 200.8 Deductions (198.9 ) (206.3 ) (193.8 ) Balance at end of fiscal year $ 49.7 $ 45.8 $ 36.5 Inventories We value substantially all U.S. inventories at the lower of cost or market, with cost determined on the LIFO basis. We value all other inventories at the lower of cost and net realizable value, with cost determined using methods that approximate cost computed on a first-in first-out inventory valuation method (“ FIFO Prior to the application of the LIFO method, our U.S. operating divisions use a variety of methods to estimate the FIFO cost of their finished goods inventories. Such methods include standard costs, or average costs computed by dividing the actual cost of goods manufactured by the tons produced and multiplying this amount by the tons of inventory on hand. Lastly, certain operations calculate a ratio, on a plant by plant basis, the numerator of which is the cost of goods sold and the denominator is net sales. This ratio is applied to the estimated sales value of the finished goods inventory. Variances and other unusual items are analyzed to determine whether it is appropriate to include those items in the value of inventory. Examples of variances and unusual items that are considered to be current period charges include, but are not limited to, abnormal production levels, freight, handling costs, and wasted materials (spoilage). Cost includes raw materials and supplies, direct labor, indirect labor related to the manufacturing process and depreciation and other factory overheads. Our inventoried spare parts are measured at average cost. Property, Plant and Equipment We state property, plant and equipment at cost less accumulated depreciation. Cost includes major expenditures for improvements and replacements that extend useful lives, increase capacity, increase revenues or reduce costs, while normal maintenance and repairs are expensed as incurred. During fiscal 2018, 2017 and 2016, we capitalized interest of approximately $8.2 million, $7.0 million and $7.6 million, respectively. For financial reporting purposes, we provide depreciation and amortization primarily on a straight-line method generally over the estimated useful lives of the assets as follows: Buildings and building improvements 15-40 years Machinery and equipment 3-25 years Transportation equipment 3-8 years Generally, our machinery and equipment have estimated useful lives between 3 and 25 years; however, select portions of machinery and equipment primarily at our mills have estimated useful lives up to 44 years. Greater than 90% of the cost of our mill assets have lives of 25 years or less. Leasehold improvements are depreciated over the shorter of the asset life or the lease term, generally between 3 and 10 years. Goodwill and Long-Lived Assets We review the carrying value of our goodwill annually at the beginning of the fourth quarter of each fiscal year, or more often if events or changes in circumstances indicate that the carrying amount may exceed fair value as set forth in ASC 350, “Intangibles — Goodwill and Other.” Note 7. Discontinued Operations The goodwill impairment model is a two-step process. An amendment to ASC 350 became effective December 2011 that allows a qualitative assessment, prior to step one, to determine whether it is more likely than not that the fair value of a reporting unit exceeds its carrying amount. We did not attempt a qualitative assessment and moved directly to step one. In step one, we utilize the present value of expected net cash flows or, as appropriate, a combination of the present value of expected net cash flows and the guideline public company method to determine the estimated fair value of our reporting units. This present value model requires management to estimate future net cash flows, the timing of these cash flows, and a discount rate (based on a weighted average cost of capital), which represents the time value of money and the inherent risk and uncertainty of the future cash flows. Factors that management must estimate when performing this step in the process include, among other items, sales volume, prices, inflation, discount rates, exchange rates, tax rates, anticipated synergies and productivity improvements resulting from acquisitions, capital expenditures and continuous improvement projects. The assumptions we use to estimate future cash flows are consistent with the assumptions that the reporting units use for internal planning purposes, updated to reflect current expectations. The guideline public company method involves comparing the reporting unit to similar companies whose stock is freely traded on an organized exchange. The fair values determined by the discounted cash flow and guideline public company methods were weighted to arrive at the concluded fair value of the reporting unit. However, in instances where comparisons to our peers is less meaningful, no weight was placed on the guideline public company method to arrive at the concluded fair value of the reporting unit. If we determine that the estimated fair value of the reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired. If we determine that the carrying amount of the reporting unit exceeds its estimated fair value, we would complete step two of the impairment analysis. Step two involves determining the implied fair value of the reporting unit’s goodwill and comparing it to the carrying amount of that goodwill. If the carrying amount of the reporting unit’s goodwill exceeds the implied fair value of that goodwill, we recognize an impairment loss in an amount equal to that excess. While ASU 2017-04, “ Simplifying the Test for Goodwill Impairment During the fourth quarter of fiscal 2018, of those reporting units that have goodwill, our Consumer Packaging reporting unit had a fair value which exceeded its carrying value by less than 10%, primarily due to the fair value accounting related to the Combination and the MPS Acquisition. If we had concluded that it was appropriate to increase the discount rate we used by 100 basis points to estimate the fair value of each reporting unit that has goodwill, the fair value of each of our reporting units would have continued to exceed its carrying value, except for the Consumer Packaging reporting unit. No events have occurred since the latest annual goodwill impairment assessment that would necessitate an interim goodwill impairment assessment. We follow the provisions included in ASC 360, “Property, Plant and Equipment” Included in our long-lived assets are certain identifiable intangible assets. These intangible assets are amortized based on the approximate pattern in which the economic benefits are consumed or straight-line if the pattern was not reliably determinable. Estimated useful lives range from 1 to 40 years and have a weighted average life of approximately 16.6 years. Our judgments regarding the existence of impairment indicators are based on legal factors, market conditions and operational performance. Future events could cause us to conclude that impairment indicators exist and that assets associated with a particular operation are impaired. Evaluating impairment also requires us to estimate future operating results and cash flows, which also require judgment by management. Any resulting impairment loss could have a material adverse impact on our financial condition and results of operations. Restructuring and Other Costs Our restructuring and other costs include primarily items such as restructuring portions of our operations, acquisition costs, integration costs and divestiture costs. We have restructured portions of our operations from time to time, have current restructuring initiatives taking place, and it is possible that we may engage in future restructuring activities. Identifying and calculating the cost to exit these operations requires certain assumptions to be made, the most significant of which are anticipated future liabilities, including severance costs, leases and other contractual obligations, and the adjustment of property, plant and equipment to net realizable value. We believe our estimates are reasonable, considering our knowledge of the industries we operate in, previous experience in exiting activities and valuations we may obtain from independent third parties. Although our estimates have been reasonably accurate in the past, significant judgment is required, and these estimates and assumptions may change as additional information becomes available and facts or circumstances change. See “ Note 3. Restructuring and Other Costs Business Combinations From time to time, we may enter into business combinations. In accordance with ASC 805, “ Business Combinations Significant estimates and assumptions in estimating the fair value of acquired technology, customer relationships, and other identifiable intangible assets include future cash flows that we expect to generate from the acquired assets. If the subsequent actual results and updated projections of the underlying business activity change compared with the assumptions and projections used to develop these values, we could record impairment charges. In addition, we have estimated the economic lives of certain acquired assets and these lives are used to calculate depreciation and amortization expense. If our estimates of the economic lives change, depreciation or amortization expenses could be increased or decreased, or the acquired asset could be impaired. Fair Value of Financial Instruments and Nonfinancial Assets and Liabilities We estimate fair values in accordance with ASC 820, “Fair Value Measurement. Financial instruments not recognized at fair value on a recurring or nonrecurring basis include cash and cash equivalents, accounts receivables, certain other current assets, short-term debt, accounts payable, certain other current liabilities and long-term debt. With the exception of long-term debt, the carrying amounts of these financial instruments approximate their fair values due to their short maturities. The fair values of our long-term debt are estimated using quoted market prices or are based on the discounted value of future cash flows. We disclose the fair value of long-term debt in “ Note 13. Debt ” “ Note 4. Retirement Plans ” Supplemental Plans We measure certain nonfinancial assets and nonfinancial liabilities at fair value on a nonrecurring basis. These assets and liabilities include cost and equity method investments when they are deemed to be other-than-temporarily impaired, assets acquired and liabilities assumed in a merger or an acquisition or in a nonmonetary exchange, and property, plant and equipment and goodwill and other intangible assets that are written down to fair value when they are held for sale or determined to be impaired. Given the nature of nonfinancial assets and liabilities, evaluating their fair value from the perspective of a market participant is inherently complex. Assumptions and estimates about future values can be affected by a variety of internal and external factors. Changes in these factors may require us to revise our estimates and could result in future impairment charges for goodwill and acquired intangible assets, or retroactively adjust provisional amounts that we have recorded for the fair values of assets and liabilities in connection with business combinations. These adjustments could have a material impact on our financial condition and results of operations. We discuss fair values in more detail in “ Note 12. Fair Value ”. Derivatives We are exposed to interest rate risk, commodity price risk and foreign currency exchange risk. To manage these risks, from time to time and to varying degrees, we may enter into a variety of financial derivative transactions and certain physical commodity transactions that are determined to be derivatives. Interest rate swaps may be entered into to manage the interest rate risk associated with a portion of our outstanding debt. Interest rate swaps are either designated for accounting purposes as cash flow hedges of forecasted floating interest payments on variable rate debt or fair value hedges of fixed rate debt, or we may elect not to treat them as accounting hedges. Swaps or forward contracts on certain commodities may be entered into to manage the price risk associated with forecasted purchases or sales of those commodities. In addition, certain commodity financial derivative contracts and physical commodity contracts that are determined to be derivatives may not be designated as accounting hedges because either they do not meet the criteria for treatment as accounting hedges under ASC 815, “Derivatives and Hedging”, Outstanding financial derivative instruments expose us to credit loss in the event of nonperformance by the counterparties to the derivative agreements. Our credit exposure related to these financial instruments is represented by the fair value of contracts reported as assets. We manage our exposure to counterparty credit risk through minimum credit standards, diversification of counterparties and procedures to monitor concentrations of credit risk. We may enter into financial derivative contracts that may contain credit-risk-related contingent features which could result in a counterparty requesting immediate payment or demanding immediate and ongoing full overnight collateralization on derivative instruments in net liability positions. For financial derivative instruments that are designated as a cash flow hedge for accounting purposes, the effective portion of the gain or loss on the financial derivative instrument is reported as a component of other comprehensive income and reclassified into earnings in the same line item associated with the forecasted transaction, and in the same period or periods during which the forecasted transaction affects earnings. Gains and losses on the financial derivative instrument representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current earnings. We have at times entered into interest rate swap agreements that effectively modified our exposure to interest rate risk by converting a portion of our interest payments on floating rate debt to a fixed rate basis, thus reducing the impact of interest rate changes on future interest expense. These agreements typically involved the receipt of floating rate amounts in exchange for fixed interest rate payments over the life of the agreements without an exchange of the underlying principal amount. At September 30, 2018, there were no interest rate or commodity derivatives outstanding, and the notional amount of foreign currency derivatives were $356.0 million. At September 30, 2017, there were no interest rate or commodity derivatives outstanding, and the notional amount of foreign currency derivatives were $47.8 million. For additional information see “ Note 13. Debt Health Insurance We are self-insured for the majority of our group health insurance costs. However, we seek to limit our health insurance costs by entering into certain stop loss insurance coverage. Due to mergers, acquisitions and other factors, we may have plans that do not include stop loss insurance. We calculate our group health insurance reserve on an undiscounted basis based on estimated reserve rates. We utilize claims lag data provided by our claims administrators to compute the required estimated reserve rate. We calculate our average monthly claims paid using the actual monthly payments during the trailing 12-month period. At that time, we also calculate our required reserve using the reserve rates discussed above. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our group health insurance costs. Workers’ Compensation We purchase large risk deductible workers’ compensation policies for the majority of our workers’ compensation liabilities that are subject to various deductibles to limit our exposure. We calculate our workers’ compensation reserves on an undiscounted basis based on estimated actuarially calculated development factors. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our workers' compensation costs. Income Taxes We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amount and the tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. All deferred tax assets and liabilities are classified as noncurrent in our consolidated balance sheet in accordance with ASU 2015-17, “ Income Taxes: Balance Sheet Classification of Deferred Taxes.” We record net deferred tax assets to the extent we believe these assets will more likely than not be realized. In making such determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies, recent financial operations and their associated valuation allowances, if any. In the event we were to determine that we would be able to realize or not realize our deferred income tax assets in the future in their net recorded amount, we would make an adjustment to the valuation allowance, which would reduce or increase the provision for income taxes, respectively. Certain provisions of ASC 740, “Income Taxes On December 22, 2017, the Tax Act was signed into law. The Tax Act contains significant changes to corporate taxation, including (i) the reduction of the corporate income tax rate to 21%, (ii) the acceleration of expensing for certain business assets, (iii) the one-time transition tax related to the transition of U.S. international tax from a worldwide tax system to a territorial tax system, (iv) the repeal of the domestic production deduction, (v) additional limitations on the deductibility of interest expense and (vi) expanded limitations on executive compensation. See “ Note 5. Income Taxes. Pension and Other Postretirement Benefits We account for pension and other postretirement benefits in accordance with ASC 715, “ Compensation – Retirement Benefits “ Note 4. Retirement Plans ”, The amount of unrecognized actuarial gains and losses recognized in the current year’s operations is based on amortizing the unrecognized gains or losses for each plan that exceed the larger of 10% of the projected benefit obligation or the fair value of plan assets, also known as “the corridor”. The amount of unrecognized gain or loss that exceeds the corridor is amortized over the average future service of the plan participants or the average life expectancy of inactive plan participants for plans where all or almost all of the plan participants are inactive. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our pension and other postretirement benefit obligations and our future expense. Share-Based Compensation We recognize expense for share-based compensation plans based on the estimated fair value of the related awards in accordance with ASC 718, “ Compensation – Stock Compensation SAR SARs “ Note 20. Share-Based Compensation ” Asset Retirement Obligations The Company accounts for asset retirement obligations in accordance with ASC 410, “ Asset Retirement and Environmental Obligations Repair and Maintenance Costs We expense routine repair and maintenance costs as we incur them. We defer certain expenses we incur during planned major maintenance activities and recognize the expenses ratably over the shorter of the estimated interval until the next major maintenance activity or the life of the deferred item. This maintenance is generally performed every twelve to twenty-four months and has a significant impact on our results of operations in the period performed primarily due to lost production during the maintenance period. Planned major maintenance costs deferred at September 30, 2018 and 2017 were $83.4 million and 80.8 million, respectively. The assets are recorded as other assets on the consolidated balance sheets. Foreign Currency We translate the assets and liabilities of our foreign operations from their functional currency into U.S. dollars at the rate of exchange in effect as of the balance sheet date. We reflect the resulting translation adjustments in equity. We translate the revenues and expenses of our foreign operations at a daily average rate prevailing for each month during the fiscal year. We include gains or losses from foreign currency transactions, such as those resulting from the settlement of foreign receivables or payables, in the consolidated statements of operations. We recorded a gain on foreign currency transactions of $12.2 million and $4.3 million Environmental Remediation Costs We accrue for losses associated with our environmental remediation obligations when it is probable that we have incurred a liability and the amount of the loss can be reasonably estimated. We generally recognize accruals for estimated losses from our environmental remediation obligations no later than completion of the remedial feasibility study and adjust such accruals as further information develops or circumstances change. We recognize recoveries of our environmental remediation costs from other parties as assets when we deem their receipt probable. See “ Note 17. Commitments and Contingencies. New Accounting Standards - Recently Adopted In May 2017, the FASB issued Compensation – Stock Compensation: Scope of Modification Accounting Compensation – Stock Compensation In March 2017, the FASB issued ASU 2017-07, “ Compensation: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The adoption resulted in a change in our operating profit, which was offset by a corresponding change in non-operating pension income (expense) to reflect the impact of presenting the non-service income (cost) component of net periodic pension income (expense) outside of operating income. In February 2017, the FASB issued ASU 2017-05, “ Other Income: Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets In January 2017, the FASB issued ASU 2017-01, “ Clarifying the Definition of a Business Business Combinations In November 2016, the FASB issued ASU 2016-18, “ Restricted Cash Statement of Cash Flows In October 2016, the FASB issued ASU 2016-16, “ Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory In August 2016, the FASB issued ASU 2016-15 “ Classification of Certain Cash Receipts and Cash Payments Statement of Cash Flows In May 2014, the FASB issued ASU 2014-09, which is codified in ASC 606 “ Revenue from Contr

Mergers, Acquisitions and Inves

Mergers, Acquisitions and Investment	12 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Mergers, Acquisitions and Investment	Note 2. Mergers, Acquisitions and Investment We account for acquisitions in accordance with ASC 805, “Business Combinations”. The estimated fair values of all assets acquired and liabilities assumed in acquisitions are provisional and may be revised as a result of additional information obtained during the measurement period of up to one year from the acquisition date. No changes in fiscal 2018 to our fiscal 2017 provisional fair value estimates of assets and liabilities assumed in acquisitions have been significant. Schlüter Acquisition On September 4, 2018, we completed the Schlüter Acquisition to further enhance our pharmaceutical and automotive platform and expand our geographical footprint in Europe to better serve our customers. In connection with the Schlüter Acquisition, we paid cash of $51.4 million. The purchase consideration included the assumption of $7.5 million of debt. since the date of the acquisition The preliminary allocation of consideration primarily included $9.1 million of customer relationship intangible assets, $23.8 million of goodwill, $27.5 million of property, plant and equipment and $21.5 million of liabilities including deferred taxes and the aforementioned debt. We are amortizing the customer relationship intangibles over 10.5 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force, as well as due to establishing deferred taxes for the difference between book and tax basis of the assets and liabilities acquired. The goodwill and intangibles are not amortizable for income tax purposes. We are in the process of reviewing the estimated fair values of all assets acquired and liabilities assumed, including, among other things, obtaining final third-party valuations of certain tangible and intangible assets, as well as the fair value of certain contracts and the determination of certain tax balances; thus, the allocation of the purchase price is preliminary and subject to revision. Plymouth Packaging Acquisition On January 5, 2018, we completed the Plymouth Packaging Acquisition to further enhance our platform and drive differentiation and innovation. Plymouth’s “Box on Demand” systems are located on customers’ sites under multi-year exclusive agreements and use fanfold corrugated to produce custom, on-demand corrugated packaging that is accurately sized for any product type according to the customers’ specifications. The estimated purchase price of $201.9 million, net of cash received of $3.1 million, is subject to an estimated payment of $25.1 million consisting of a deferred payment and a tax make-whole payment related to stepping up the assets for tax purposes. We expect the payment to be made in the first quarter of fiscal 2019. We have included the financial results of the acquired assets in our Corrugated Packaging segment . The preliminary allocation of consideration primarily included $61.9 million of customer relationship intangible assets, $58.7 million of goodwill, $35.2 million of property, plant and equipment, $26.2 million of other long-term assets consisting of assets leased to customers and equity method investments, and $12.6 million of liabilities. We are amortizing the customer relationship intangibles over 13.0 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force, as well as due to establishing deferred taxes for the difference between book and tax basis of the assets and liabilities acquired. The goodwill and intangibles are amortizable for income tax purposes. We are in the process of reviewing the estimated fair values of all assets acquired and liabilities assumed, including, among other things, obtaining final third-party valuations of certain tangible and intangible assets, as well as the fair value of certain contracts and the determination of certain tax balances; thus, the allocation of the purchase price is preliminary and subject to revision. Grupo Gondi Investment On April 1, 2016, we completed the formation of a joint venture with Grupo Gondi in Mexico. We contributed $175.0 million in cash and the stock of an entity that owns three corrugated packaging facilities in Mexico in return for a 25.0% ownership interest in the joint venture together with future put and call rights. The investment was valued at approximately $0.3 billion. The majority equity holders manage the joint venture and we provide technical and commercial resources and supply certain paperboard to the joint venture. We believe the joint venture is helping to grow our presence in the attractive Mexican market. The joint venture operates paper machines, corrugated packaging and high graphic folding carton facilities across various production sites. As a result of the transaction, we recorded a pre-tax non-cash gain of $12.1 million included in “Other income, net” on our consolidated statements of operations in fiscal 2016. We have included the financial results of the joint venture in our Corrugated Packaging segment since the date of the formation, and are accounting for the investment under the equity method. On October 20, 2017, we increased our ownership interest in Grupo Gondi from 27.0% to 32.3% through a $108 million capital contribution, which followed the joint venture entity having a stock redemption from a minority partner in April 2017 that increased our ownership interest to approximately 27.0%. The October 2017 capital contribution is being used to support the joint venture’s capital expansion plans, which include a containerboard mill and several converting plants. The agreement governing our investment in Grupo Gondi continues to include future put and call rights with respect to the respective parties’ ownership interest in the joint venture. Hannapak Acquisition On August 1, 2017, we completed the Hannapak Acquisition in a stock purchase. Hanna Group is one of Australia’s leading providers of folding cartons to a variety of markets, including beverage, food, confectionery, and healthcare. We expect this acquisition will build on our established and growing packaging business in the region. The purchase consideration for the Hannapak Acquisition was $61.4 million, net of cash received of $0.6 million. We have included the financial results of the acquired operations since the date of the acquisition in our Consumer Packaging segment. The allocation of consideration primarily included $22.2 million of customer relationship intangible assets, $25.3 million of goodwill, $9.8 million of property, plant and equipment and $13.9 million of liabilities including deferred taxes. We are amortizing the customer relationship intangibles over 13 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force, as well as due to establishing deferred taxes for the difference between book and tax basis of the assets and liabilities acquired Island Container Acquisition On July 17, 2017, we completed the Island Container Acquisition in an asset purchase. The assets acquired include a corrugator and corrugated converting operations located in Wheatley Heights, New York, and certain related fulfillment assets located in Saddle Brook, New Jersey. We have substantially completed the integration of the 80,000 tons of containerboard used by Island annually. The purchase consideration for the Island Container Acquisition was $84.7 million, including a working capital settlement of $1.2 million paid in fiscal 2018. We have included the financial results of the acquired assets since the date of the acquisition in our Corrugated Packaging segment. The allocation of consideration primarily included $43.0 million of customer relationship intangible assets, $27.2 million of goodwill, $5.4 million of property, plant and equipment and $0.8 million of liabilities. We are amortizing the customer relationship intangibles over 8.5 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force. The goodwill and intangibles are amortizable for income tax purposes. U.S. Corrugated Acquisition On June 9, 2017, we completed the U.S. Corrugated Acquisition in a stock purchase. We acquired five corrugated converting facilities in Ohio, Pennsylvania and Louisiana that provide a comprehensive suite of products and services to customers in a variety of end markets, including food & beverage, pharmaceuticals and consumer electronics. At the time of the transaction, we expected the acquisition to provide us the opportunity to increase the vertical integration of our Corrugated Packaging segment by approximately 105,000 tons of containerboard annually through the acquired facilities and another 50,000 tons under a long-term supply contract with another company owned by the seller, and we have since completed the integration of these tons. The purchase consideration was $193.7 million, net of cash received of $1.4 million and a $3.4 million working capital settlement received in fiscal 2018. The consideration included the issuance of 2.4 million shares of Common Stock valued at $136.1 million. We have included the financial results of U.S. Corrugated since the date of the acquisition in our Corrugated Packaging segment. The allocation of consideration primarily included $77.8 million of customer relationship intangible assets, $110.5 million of goodwill, $30.0 million of property, plant and equipment and $55.5 million of liabilities, including deferred income taxes. We are amortizing the customer relationship intangibles over 7.5 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force, as well as due to establishing deferred taxes for the difference between book and tax basis of the assets and liabilities acquired. The goodwill and intangibles are not amortizable for income tax purposes. MPS Acquisition On June 6, 2017, we completed the MPS Acquisition in a stock purchase. MPS is a global provider of print-based specialty packaging solutions and its differentiated product offering includes premium folding cartons, inserts, labels and rigid packaging. We acquired the outstanding shares of MPS for $18.00 per share in cash and the assumption of debt. We believe the acquisition will increase our annual paperboard consumption by approximately 225,000 tons. We are well underway, and In connection with the MPS Acquisition, we paid cash of $1,351.1 million, net of cash received of $47.5 million. The purchase consideration included the assumption of $929.1 million of debt and $1.9 million related to MPS equity awards that were replaced with WestRock equity awards with identical terms for the pre-acquisition service. The amount related to post-acquisition service is being expensed over the remaining service period of the awards. See “ Note 20. Share-Based Compensation The allocation of consideration primarily included $1,026.4 million of intangible assets, $900.9 million of goodwill, $469.9 million of property, plant and equipment and $1,561.6 million of liabilities and noncontrolling interests, including debt and deferred income taxes. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), the assembled work force, as well as due to establishing deferred taxes for the difference between book and tax basis of the assets and liabilities acquired. The goodwill and intangibles are not amortizable for income tax purposes. The following table summarizes the weighted average life and the allocation to intangible assets recognized in the MPS Acquisition, excluding goodwill (in millions): Weighted Avg. Life Amounts Recognized as of the Acquisition Date Customer relationships 14.6 $ 1,008.7 Trademarks and tradenames 3.0 15.2 Photo library 10.0 2.5 Total 14.4 $ 1,026.4 None of the intangibles has significant residual value. We are amortizing the customer relationship intangibles over estimated useful lives ranging from 13 to 16 years based on a straight-line basis because the amortization pattern was not reliably determinable. Star Pizza Acquisition On March 13, 2017, we completed the Star Pizza Acquisition. The transaction provided us with a leadership position in the fast growing small-run pizza box market and increases our vertical integration. The purchase price was $34.6 million, net of a $0.7 million working capital settlement. We have fully integrated the approximately 22,000 tons of containerboard used by Star Pizza annually. We have included the financial results of the acquired assets since the date of the acquisition in our Corrugated Packaging segment. The purchase price allocation for the acquisition primarily included $24.8 million of customer relationship intangible assets and $2.2 million of goodwill. We are amortizing the customer relationship intangibles over 10 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force. The goodwill and intangibles are amortizable for income tax purposes. Packaging Acquisition On January 19, 2016, we completed the Packaging Acquisition. The entities acquired provide value-added folding carton and litho-laminated display packaging solutions. The purchase price was $94.1 million, net of cash received of $1.7 million, a working capital settlement and a $3.5 million escrow receipt in the first quarter of fiscal 2017. The transaction is subject to an election under Section 338(h)(10) of the Code that increases the U.S. tax basis in the acquired U.S. entities. We believe the transaction has provided us with attractive and complementary customers, markets and facilities. We have included the financial results of the acquired entities since the date of the acquisition in our Consumer Packaging segment. The purchase price allocation for the acquisition primarily included $55.0 million of property, plant and equipment, $10.5 million of customer relationship intangible assets, $9.3 million of goodwill and $25.8 million of liabilities, including $1.3 million of debt. We are amortizing the customer relationship intangibles over estimated useful lives ranging from 9 to 15 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), and the assembled work force. The goodwill and intangibles of the U.S. entities are amortizable for income tax purposes. SP Fiber On October 1, 2015, we completed the SP Fiber Acquisition in a stock purchase. The transaction included the acquisition of mills located in Dublin, GA and Newberg, OR, which produce lightweight recycled containerboard and kraft and bag paper. The Newberg mill also produced newsprint. As part of the transaction, we also acquired SP Fiber's 48% interest in GPS. GPS is a joint venture providing steam to the Dublin mill and electricity to Georgia Power. The purchase price was $278.8 million, net of cash received of $9.2 million and a working capital settlement. In addition, we paid $36.5 million for debt owed by GPS and thereby own the majority of the debt issued by GPS. The Dublin mill has helped balance the fiber mix of our mill system, including our ability to serve the increasing demand for lighter weight containerboard, and the addition of kraft and bag paper has diversified our product offering. Subsequent to the transaction, we announced the permanent closure of the Newberg mill due to the decline in market conditions of the newsprint business and our need to balance supply and demand in our containerboard system. We determined GPS should be consolidated as a variable interest entity under ASC 810 “ Consolidation The purchase price allocation for the acquisition primarily included $324.8 million of property, plant and equipment, $13.5 million of customer relationship intangible assets, $57.3 million of goodwill, and $150.3 million of liabilities and noncontrolling interests, including $13.7 million of debt primarily owed by GPS to third parties. We are amortizing the customer relationship intangibles over 20 years based on a straight-line basis because the amortization pattern was not reliably determinable. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the acquisition (e.g., enhanced reach of the combined organization and other synergies), the assembled work force of SP Fiber as well as due to establishing deferred taxes for the difference between the book to tax basis of the assets and liabilities acquired. The goodwill and intangibles are not amortizable for income tax purposes.

Restructuring and Other Costs

Restructuring and Other Costs	12 Months Ended
	Sep. 30, 2018
Restructuring And Other Costs [Abstract]
Restructuring and Other Costs	Note 3. Restructuring and Other Costs Summary of Restructuring and Other Initiatives We recorded pre-tax restructuring and other costs of $105.4 million, $196.7 million and $366.4 million for fiscal 2018, 2017 and 2016, respectively. Of these costs, $27.0 million, $86.6 million and $200.2 Note 7. Discontinued Operations The following table summarizes our Restructuring and other costs for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Restructuring $ 39.5 $ 113.4 $ 294.9 Other 65.9 83.3 71.5 Restructuring and Other Costs $ 105.4 $ 196.7 $ 366.4 Restructuring Our restructuring charges are primarily associated with costs of plant closures and employee costs due to merger and acquisition-related workforce reductions. When we close a facility, if necessary, we recognize a write-down to reduce the carrying value of equipment or other property to their estimated fair value less cost to sell, and record charges for severance and other employee-related costs. Any subsequent change in fair value less cost to sell prior to disposition is recognized as identified; however, no gain is recognized in excess of the cumulative loss previously recorded unless the actual selling price exceeds the original carrying value when sold. At the time of each announced closure, we generally expect to record future period costs for equipment relocation, facility carrying costs, costs to terminate a lease or contract before the end of its term and employee-related costs. Although specific circumstances vary, our strategy has generally been to consolidate our sales and operations into large well-equipped plants that operate at high utilization rates and take advantage of available capacity created by operational excellence initiatives and/or further optimize our system following mergers and acquisitions or a changing business environment. Therefore, we have transferred a substantial portion of each closed plant’s assets and production to our other plants. We believe these actions have allowed us to more effectively manage our business. In our Land and Development segment, the restructuring charges primarily consisted of severance and other employee costs associated with the accelerated monetization strategy and wind-down of operations and lease costs. While restructuring costs are not charged to our segments and, therefore, do not reduce segment income, we highlight the segment to which the charges relate. The following table presents a summary of restructuring charges related to active restructuring initiatives that we incurred during the last three fiscal years, the cumulative recorded amount since we started the initiative, and our estimate of the total we expect to incur (in millions): 2018 2017 2016 Cumulative Total Expected Corrugated Packaging Net property, plant and equipment costs $ 2.8 $ 1.4 $ 184.5 $ 211.5 $ 211.5 Severance and other employee costs 1.6 3.3 17.4 42.2 42.8 Equipment and inventory relocation costs 3.1 1.9 0.3 7.1 7.1 Facility carrying costs 3.2 5.4 18.9 36.7 37.9 Other costs (0.1 ) (1.2 ) 9.1 19.1 19.1 Restructuring total $ 10.6 $ 10.8 $ 230.2 $ 316.6 $ 318.4 Consumer Packaging Net property, plant and equipment costs $ 6.9 $ 28.3 $ 3.8 $ 41.6 $ 41.6 Severance and other employee costs 7.2 26.4 4.6 41.0 41.2 Equipment and inventory relocation costs 2.7 2.8 1.1 7.4 7.9 Facility carrying costs 1.0 0.7 0.5 3.4 4.0 Other costs (1) 2.2 20.2 — 22.9 22.9 Restructuring total $ 20.0 $ 78.4 $ 10.0 $ 116.3 $ 117.6 Land and Development Net property, plant and equipment costs $ — $ 1.8 $ — $ 1.8 $ 1.8 Severance and other employee costs 0.3 2.8 10.6 13.7 13.7 Other costs 3.0 $ — $ — 3.0 3.0 Restructuring total $ 3.3 $ 4.6 $ 10.6 $ 18.5 $ 18.5 Corporate Net property, plant and equipment costs $ — $ 0.1 $ 1.2 $ 1.4 $ 1.4 Severance and other employee costs 0.8 14.8 36.9 100.6 100.6 Other costs 4.8 4.7 6.0 15.5 15.5 Restructuring total $ 5.6 $ 19.6 $ 44.1 $ 117.5 $ 117.5 Total Net property, plant and equipment costs $ 9.7 $ 31.6 $ 189.5 $ 256.3 $ 256.3 Severance and other employee costs 9.9 47.3 69.5 197.5 198.3 Equipment and inventory relocation costs 5.8 4.7 1.4 14.5 15.0 Facility carrying costs 4.2 6.1 19.4 40.1 41.9 Other costs 9.9 23.7 15.1 60.5 60.5 Restructuring total $ 39.5 $ 113.4 $ 294.9 $ 568.9 $ 572.0 (1) Includes a $17.6 million impairment of a customer relationship intangible in fiscal 2017 related to an exited product line. We have defined “ Net property, plant and equipment costs Note 3 Other Costs Our other costs consist of acquisition, integration and divestiture costs. We incur costs when we acquire or divest businesses. Acquisition costs include costs associated with transactions, whether consummated or not, such as advisory, legal, accounting, valuation and other professional or consulting fees, as well as potential litigation costs associated with those activities. We incur integration costs pre- and post-acquisition that reflect work being performed to facilitate merger and acquisition integration, such as work associated with information systems and other projects including spending to support future acquisitions, and primarily consist of professional services. Divestiture costs consist primarily of similar professional fees. The divestiture costs in fiscal 2017 were primarily associated with costs incurred during the HH&B Sale process. We consider acquisition, integration and divestiture costs to be Corporate costs regardless of the segment or segments involved in the transaction. The following table presents our acquisition, divestiture and integration costs that we incurred during the last three fiscal years (in millions): 2018 2017 2016 Acquisition costs $ 38.2 $ 27.1 $ 8.9 Integration costs 27.4 46.4 62.1 Divestiture costs 0.3 9.8 0.5 Other total $ 65.9 $ 83.3 $ 71.5 The following table summarizes the changes in the restructuring accrual, which are primarily composed of lease commitments, accrued severance and other employee costs, and a reconciliation of the restructuring accrual charges to the line item “ Restructuring and other costs ” on our consolidated statements of operations for the last three fiscal years (in millions): 2018 2017 2016 Accrual at beginning of fiscal year $ 47.4 $ 44.8 $ 21.4 Accruals acquired in acquisition — 3.5 — Additional accruals 16.5 63.2 75.3 Payments (29.8 ) (53.3 ) (51.9 ) Adjustment to accruals (1.0 ) (10.8 ) — Foreign currency rate changes (1.5 ) — — Accrual at end of fiscal year $ 31.6 $ 47.4 $ 44.8 Reconciliation of accruals and charges to restructuring and other costs (in millions): 2018 2017 2016 Additional accruals and adjustments to accruals (see table above) $ 15.5 $ 52.4 $ 75.3 Acquisition costs 38.2 27.1 8.9 Integration costs 22.0 41.2 59.8 Divestiture costs 0.3 9.8 0.5 Net property, plant and equipment 9.7 31.6 189.5 Severance and other employee costs 1.3 3.8 11.5 Equipment and inventory relocation costs 5.8 4.7 1.4 Facility carrying costs 4.2 6.1 19.5 Other costs 8.4 20.0 — Total restructuring and other costs, net $ 105.4 $ 196.7 $ 366.4

Retirement Plans

Retirement Plans	12 Months Ended
	Sep. 30, 2018
Retirement Plans [Abstract]
Retirement Plans	Note 4. We have defined benefit pension plans and other postretirement benefit plans for certain U.S. and non-U.S. employees. Certain plans were frozen for salaried and non-union hourly employees at various times in the past, although some employees meeting certain criteria are still accruing benefits. In addition, we participate in several MEPPs that provide retirement benefits to certain union employees in accordance with various collective bargaining agreements. We also have supplemental executive retirement plans and other non-qualified defined benefit pension plans that provide unfunded supplemental retirement benefits to certain of our current and former executives. The supplemental executive retirement plans provide for incremental pension benefits in excess of those offered in the Plan. The other postretirement benefit plans provide certain health care and life insurance benefits for certain salaried and hourly employees who meet specified age and service requirements as defined by the plans. The benefits under our defined benefit pension plans are based on either compensation or a combination of years of service and negotiated benefit levels, depending upon the plan. We allocate our pension assets to several investment management firms across a variety of investment styles. Our defined benefit Investment Committee meets at least four times a year with our investment advisors to review each management firm’s performance and monitors its compliance with its stated goals, our investment policy and applicable regulatory requirements in the U.S., Canada, and other jurisdictions. Investment returns vary. We believe that, by investing in a variety of asset classes and utilizing multiple investment management firms, we can create a portfolio that yields adequate returns with reduced volatility. Our qualified U.S. plans employ a liability matching strategy augmented with Treasury futures to generally fully hedge against interest rate risk. After we consulted with our actuary and investment advisors, we adopted the target allocations in the table that follows for our pension plans to produce the desired performance. These target allocations are guidelines, not limitations, and occasionally plan fiduciaries will approve allocations above or below target ranges or modify the allocations. Target Allocations U.S. Plans Non-U.S. Plans 2018 2017 2018 2017 Equity investments 15% 15% 22% 24% Fixed income investments 75% 70% 70% 65% Short-term investments 1% 1% 1% 1% Other investments 9% 14% 7% 10% Total 100% 100% 100% 100% Our asset allocations by asset category at September 30 were as follows: U.S. Plans Non-U.S. Plans 2018 2017 2018 2017 Equity investments 14% 13% 23% 26% Fixed income investments 73% 73% 69% 64% Short-term investments 3% 3% 2% 3% Other investments 10% 11% 6% 7% Total 100% 100% 100% 100% We manage our retirement plans in accordance with the provisions of the Employee Retirement Income Security Act of 1974, as amended, and the rules and regulations thereunder (“ ERISA In developing our weighted average expected rate of return on plan assets, we consulted with our investment advisors and evaluated criteria based on historical returns by asset class and long-term return expectations by asset class. We use a September 30 measurement date. We expect to contribute approximately $22 million to our U.S. and non-U.S. pension plans in fiscal 2019. However, it is possible that our assumptions or legislation may change, actual market performance may vary or we may decide to contribute a different amount. Therefore, the amount we contribute may vary materially. The expense for MEPPs for collective bargaining employees generally equals the contributions for these plans, excluding estimated accruals for withdrawal liabilities. The weighted average assumptions used to measure the benefit plan obligations at September 30, were: Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.50 % 3.42 % 4.09 % 3.26 % Rate of compensation increase 3.00 % 2.67 % 3.00 % 3.17 % We determine the discount rate with the assistance of actuaries. At September 30, 2018, the discount rate for the U.S. pension plans was determined based on the yield on a theoretical portfolio of high-grade corporate bonds, and the discount rate for the non-U.S. plans was determined based on a yield curve developed by our actuary. The theoretical portfolio of high-grade corporate bonds used to select the September 30, 2018 discount rate for the U.S. pension plans includes bonds generally rated Aa- or better with at least $100 million outstanding par value and bonds that are non-callable (unless the bonds possess a “make whole” feature). The theoretical portfolio of bonds has cash flows that generally match our expected benefit payments in future years. Our assumption regarding the future rate of compensation increases is reviewed periodically and is based on both our internal planning projections and recent history of actual compensation increases. We typically review our expected long-term rate of return on plan assets periodically through an asset allocation study with either our actuary or investment advisor. In fiscal 2019, our expected rate of return used to determine net periodic benefit cost is 6.50% for our U.S. plans and 4.69% for our non-U.S. plans. Our expected rates of return in fiscal 2019 are based on an analysis of our long-term expected rate of return and our current asset allocation. During the second quarter of fiscal 2017, our year-to-date lump sum payments to certain beneficiaries of the Plan, together with several one-time severance benefit payments out of the Plan, triggered pension settlement accounting and a remeasurement of the Plan as of February 28, 2017. As a result of settlement accounting, we recognized as a current period expense a pro-rata portion of the unamortized net actuarial loss, after remeasurement, and recorded a $28.7 million non-cash charge to our earnings in the second quarter of 2017. The lump sum payments were to certain eligible former employees who were not currently receiving a monthly benefit. Eligible former employees whose present value of future pension benefits exceeded a certain minimum threshold had the option to either voluntarily accept lump sum payments or to not accept the offer and continue to be entitled to their monthly benefit upon retirement. Lump sum and one-time severance benefits payments of $203.7 million were made out of existing assets of the Plan in the first half of fiscal 2017. The discount rate used in the plan remeasurement was 4.49%, an increase from 4.04% for the Plan at September 30, 2016. The expected long-term rate of return on plan assets was unchanged. As a result of the February 28, 2017 remeasurement, the funded status of the Plan increased by $73.2 million as compared to September 30, 2016. The increase in the funded status was primarily due to a reduction in the plan obligations due to the increase in the discount rate. In the second half of fiscal 2017, we made $ 27.1 million in lump sum payments to certain beneficiaries of the Plan, resulting in total fiscal 2017 lump sum payments of $230.8 million and a total fiscal 2017 non-cash charge to our earnings of $32.6 million. On September 21, 2016, we used plan assets to settle $2.5 billion in pension obligations of the Plan by purchasing group annuity contracts from Prudential. This transaction transferred payment responsibility to Prudential for retirement benefits owed to approximately 35,000 U.S. retirees and their beneficiaries. As a result of the transaction, we recorded a non-cash charge of $370.7 million pre-tax. The settlement reduced our overall U.S. pension obligations and assets by approximately 40%. The monthly retirement benefit payment amounts currently received by retirees and their beneficiaries did not change as a result of this transaction. Those Plan participants not included in the transaction remain in the Plan, and responsibility for payment of the retirement benefits remains with us. In October 2014, we entered into a master agreement with the USW that applied to substantially all of our legacy RockTenn facilities represented by the USW at that time. The agreement has a six year term and covers a number of specific items, including wages, medical coverage and certain other benefit programs, substance abuse testing and successorship. Individual facilities will continue to have local agreements for subjects not covered by the master agreement and those agreements will continue to have staggered terms. The following table shows the changes in benefit obligation and plan assets, and the plan’s funded status for the years ended September 30 (in millions): Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Change in projected benefit obligation: Benefit obligation at beginning of fiscal year $ 3,941.9 $ 1,502.2 $ 4,231.7 $ 925.2 Service cost 36.7 8.0 38.0 7.1 Interest cost 157.7 46.9 165.2 32.6 Amendments 9.3 — 3.5 — Actuarial gain (186.8 ) (90.3 ) (149.1 ) (57.6 ) Plan participant contributions — 2.5 — 1.7 Special termination benefits — — 12.5 — Benefits paid (175.3 ) (82.8 ) (141.4 ) (65.1 ) Business combinations — 3.5 — 621.0 Curtailments — (0.7 ) — — Settlements — (5.5 ) (229.3 ) (0.4 ) Foreign currency rate changes — (43.6 ) — 65.1 Other adjustments — — 10.8 — Business divestitures — — — (27.4 ) Benefit obligation at end of fiscal year $ 3,783.5 $ 1,340.2 $ 3,941.9 $ 1,502.2 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ 4,107.9 $ 1,414.7 $ 4,301.5 $ 774.1 Actual (loss) gain on plan assets (24.9 ) 39.9 104.2 2.4 Employer contributions 13.5 24.2 15.3 19.2 Plan participant contributions — 2.5 — 1.7 Benefits paid (175.3 ) (82.8 ) (141.4 ) (65.1 ) Business combinations — 0.7 — 622.1 Settlements — (5.5 ) (229.3 ) (0.4 ) Business divestitures — — — (0.7 ) Foreign currency rate changes — (43.5 ) — 61.4 Other adjustments — — 57.6 — Fair value of plan assets at end of fiscal year $ 3,921.2 $ 1,350.2 $ 4,107.9 $ 1,414.7 Funded status $ 137.7 $ 10.0 $ 166.0 $ (87.5 ) Amounts recognized in the consolidated balance sheet: Non-current assets $ 305.7 $ 114.3 $ 340.4 $ 27.6 Other current liability (10.1 ) (0.9 ) (9.3 ) (0.8 ) Accrued pension and other long-term benefits (157.9 ) (103.4 ) (165.1 ) (114.3 ) Over (under) funded status at end of fiscal year $ 137.7 $ 10.0 $ 166.0 $ (87.5 ) Although the U.S. pension plans were in a net over funded position at September 30, 2018, certain U.S. plans have benefit obligations in excess of plan assets. These plans, that consist primarily of non-qualified plans, have aggregate projected benefit obligations of $197.0 million, aggregate accumulated benefit obligations of $195.3 million, and aggregate fair value of plan assets of $29.5 million at September 30, 2018. The accumulated benefit obligation of U.S. and non-U.S. pension plans was $5,081.3 million and $5,390.7 million at September 30, 2018 and 2017, respectively. The pre-tax amounts in accumulated other comprehensive loss at September 30 not yet recognized as components of net periodic pension cost, including noncontrolling interest, consist of (in millions): Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial loss $ 631.2 $ 105.6 $ 547.3 $ 173.9 Prior service cost 32.3 0.3 27.6 0.4 Total accumulated other comprehensive loss $ 663.5 $ 105.9 $ 574.9 $ 174.3 The pre-tax amounts recognized in other comprehensive (income) loss, including noncontrolling interest, are as follows at September 30 (in millions): Pension Plans 2018 2017 2016 Net actuarial loss (gain) arising during period $ 38.7 $ (48.8 ) $ 355.4 Amortization and settlement recognition of net actuarial loss (20.6 ) (57.7 ) (381.6 ) Prior service cost arising during period 9.3 3.4 1.5 Amortization of prior service cost (4.7 ) (4.1 ) (3.9 ) Net other comprehensive loss (income) recognized $ 22.7 $ (107.2 ) $ (28.6 ) The net periodic pension cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Pension Plans 2018 2017 2016 Service cost $ 44.8 $ 45.1 $ 51.4 Interest cost 204.6 197.8 310.3 Expected return on plan assets (328.4 ) (313.1 ) (412.3 ) Amortization of net actuarial loss 21.2 25.4 11.0 Amortization of prior service cost 4.7 4.1 3.9 Curtailment gain (0.6 ) — (1.6 ) Settlement (gain) loss (0.5 ) 32.7 370.7 Special termination benefits — 12.5 18.4 Company defined benefit plan (income) expense (54.2 ) 4.5 351.8 Multiemployer and other plans 1.4 4.7 5.8 Net pension (income) cost $ (52.8 ) $ 9.2 $ 357.6 The Multiemployer and other plans line in the table above excludes the estimated withdrawal liabilities recorded in fiscal 2018. For additional information, see “ Note 4. Retirement Plans — Multiemployer Plans Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Pension Plans 2018 2017 2016 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.09 % 3.26 % 4.30 % 3.08 % 4.70 % 3.89 % Rate of compensation increase 3.00 % 2.65 % 3.00 % 3.09 % 2.50 % 3.10 % Expected long-term rate of return on plan assets 6.50 % 4.98 % 6.50 % 6.03 % 5.88 % 6.34 % In fiscal 2018, 2017 and 2016, for our U.S. pension and postretirement plans, we considered the mortality tables from the Society of Actuaries and evaluated our mortality experience to establish mortality assumptions. Based on our experience and in consultation with our actuaries, we utilized the base RP-2014 mortality tables with a gender and job classification specific increase, and applied an improvement scale with generational improvements that is generally based on Social Security Administration analysis and assumptions. The increases for fiscal 2018 were 10% for white collar males, 14% for blue collar males, 11% for white collar females, and 10% for blue collar females. The increases for fiscal 2017 were 9% for white collar males, 12% for blue collar males, 11% for white collar females, and 9% for blue collar females. The increases for fiscal 2016 were 6% for white collar males, 10% for blue collar males, 12% for white collar females, and 19% for blue collar females. In fiscal 2018, 2017 and 2016 our Canadian pension and postretirement plans utilized the 2014 Private Sector Canadian Pensioners Mortality Table adjusted to reflect industry and our mortality experience and applied Canadian Pensioner’s Mortality Improvement Scale B with generational improvements. The estimated losses that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2019 are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Actuarial loss $ 22.7 $ 5.3 Prior service cost 5.2 0.1 Total $ 27.9 $ 5.4 Our projected estimated benefit payments (unaudited), which reflect expected future service, as appropriate, are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Fiscal 2019 $ 209.1 $ 80.1 Fiscal 2020 $ 218.6 $ 80.9 Fiscal 2021 $ 223.0 $ 79.8 Fiscal 2022 $ 231.7 $ 80.0 Fiscal 2023 $ 218.5 $ 80.2 Fiscal Years 2024 – 2028 $ 1,168.9 $ 398.9 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2018 (in millions): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Equity securities: U.S. equities (1) $ 165.5 $ 165.5 $ — Non-U.S. equities (1) 8.2 8.2 — Fixed income securities: U.S. government securities (2) 435.8 — 435.8 Non-U.S. government securities (3) 127.5 — 127.5 U.S. corporate bonds (3) 1,493.6 108.4 1,385.2 Non-U.S. corporate bonds (3) 380.8 49.3 331.5 Other fixed income (4) 319.4 — 319.4 Short-term investments (5) 149.0 149.0 — Benefit plan assets measured in the fair value hierarchy $ 3,079.8 $ 480.4 $ 2,599.4 Assets measured at NAV (6) 2,191.6 Total benefit plan assets $ 5,271.4 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2017 (in millions): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Equity securities: U.S. equities (1) $ 136.7 $ 136.6 $ 0.1 Non-U.S. equities (1) 40.0 40.0 — Fixed income securities: U.S. government securities (2) 452.0 — 452.0 Non-U.S. government securities (3) 130.0 — 130.0 U.S. corporate bonds (3) 1,515.4 92.3 1,423.1 Non-U.S. corporate bonds (3) 373.7 51.1 322.6 Mortgage-backed securities (3) 0.1 — 0.1 Other fixed income (4) 311.4 — 311.4 Short-term investments (5) 184.6 184.6 — Benefit plan assets measured in the fair value hierarchy $ 3,143.9 $ 504.6 $ 2,639.3 Assets measured at NAV (6) 2,378.7 Total benefit plan assets $ 5,522.6 (1) Equity securities are comprised of the following investment types: (i) common stock, (ii) preferred stock and (iii) equity exchange traded funds. Level 1 investments in common and preferred stocks and exchange traded funds are valued using quoted market prices multiplied by the number of shares owned. (2) U.S. government securities include treasury and agency debt. These investments are valued using broker quotes in an active market. (3) The level 1 non-U.S. government securities investment is an exchange traded fund valued using quoted market prices. The level 1 U.S. corporate bonds category is primarily comprised of U.S. dollar denominated investment grade securities and valued using quoted market prices. Level 2 investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads, and/or other applicable reference data. (4) Other fixed income is comprised of municipal and asset-backed securities. Investments are valued utilizing a market approach that includes various valuation techniques and sources, such as broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads and/or other applicable reference data. (5) Short-term investments are valued at $1.00/unit, which approximates fair value. Amounts are generally invested in interest-bearing accounts. (6) NAV The following table summarizes assets measured at fair value based on NAV per share as a practical expedient as of September 30, 2018 and 2017 (in millions): Fair value Redemption Frequency Redemption Notice Period Unfunded Commitments September 30, 2018 Hedge funds (1) $ 47.9 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,092.9 Monthly Up to 60 days 75.3 Fixed income and fixed income related instruments (3) 1,050.8 Monthly Up to 10 days — $ 2,191.6 $ 75.3 September 30, 2017 Hedge funds (1) $ 64.2 Quarterly Up to 91 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,207.6 Monthly Up to 60 days 98.8 Fixed income and fixed income related instruments (3) 1,106.9 Monthly Up to 10 days — $ 2,378.7 $ 98.8 (1) Hedge fund investments are primarily made through shares of limited partnerships or similar structures. Hedge funds are typically valued monthly by third-party administrators that have been appointed by the funds’ general partners. Hedge funds have been valued using NAV as a practical expedient. (2) Commingled fund investments are valued at the net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled funds have been valued using NAV as a practical expedient. (3) Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled debt funds have been valued using NAV as a practical expedient. We maintain holdings in certain private equity partnerships and private real estate investments for which a liquid secondary market does not exist. The private equity partnerships are commingled investments. Valuation techniques, such as discounted cash flow and market based comparable analyses, are used to determine fair value of the private equity investments. Unobservable inputs used for the discounted cash flow technique include projected future cash flows and the discount rate used to calculate present value. Unobservable inputs used for the market-based comparisons technique include earnings before interest, taxes, depreciation and amortization multiples in other comparable third-party transactions, price to earnings ratios, liquidity, current operating results, as well as input from general partners and other pertinent information. Private equity investments have been valued using NAV as a practical expedient. Private real estate investments are commingled investments. Valuation techniques, such as discounted cash flow and market based comparable analyses, are used to determine fair value of the private equity investments. Unobservable inputs used for the discounted cash flow technique include projected future cash flows and the discount rate used to calculate present value. Unobservable inputs used for the market-based comparison technique include a combination of third party appraisals, replacement cost, and comparable market prices. Private real estate investments have been valued using NAV as a practical expedient. Equity-related investments are hedged equity investments in a commingled fund that consist primarily of equity indexed investments which are hedged by options and also hold collateral in the form of short term treasury securities. Equity related investments have been valued using NAV as a practical expedient. Postretirement Plans The postretirement benefit plans provide certain health care and life insurance benefits for certain salaried and hourly employees who meet specified age and service requirements as defined by the plans. The weighted average assumptions used to measure the benefit plan obligations at September 30 were: Postretirement plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.50 % 6.61 % 4.09 % 6.51 % Rate of compensation increase N/A N/A N/A 7.37 % The following table shows the changes in benefit obligation and plan assets, and the plan’s funded status for the fiscal years ended September 30 (in millions): Postretirement Plans 2018 2017 Change in projected benefit obligation: U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Benefit obligation at beginning of fiscal year $ 98.1 $ 68.1 $ 90.7 $ 62.6 Service cost 0.7 0.8 0.1 0.8 Interest cost 3.9 4.0 3.3 4.1 Amendments (1.4 ) — (3.4 ) (1.0 ) Actuarial (gain) loss (2.5 ) (5.2 ) 14.1 0.4 Benefits paid (7.8 ) (2.6 ) (8.0 ) (2.7 ) Business combinations — — 1.3 2.0 Business divestitures — — — (0.4 ) Curtailments — (2.1 ) — (0.3 ) Foreign currency rate changes — (7.5 ) — 2.6 Benefit obligation at end of fiscal year $ 91.0 $ 55.5 $ 98.1 $ 68.1 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ — $ — $ — $ — Employer contributions 7.8 2.6 8.0 2.7 Plan participant contributions — — — — Benefits paid (7.8 ) (2.6 ) (8.0 ) (2.7 ) Fair value of plan assets at end of fiscal year $ — $ — $ — $ — Funded Status $ (91.0 ) $ (55.5 ) $ (98.1 ) $ (68.1 ) Amounts recognized in the consolidated balance sheet: Other current liability $ (8.8 ) $ (2.9 ) $ (9.8 ) $ (3.0 ) Accrued postretirement and other long-term benefits (82.2 ) (52.6 ) (88.3 ) (65.1 ) Under funded status at end of fiscal year $ (91.0 ) $ (55.5 ) $ (98.1 ) $ (68.1 ) The pre-tax amounts in accumulated other comprehensive loss at September 30 not yet recognized as components of net periodic postretirement cost, including noncontrolling interest, consist of (in millions): Postretirement Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial (gain) loss $ (11.2 ) $ (3.8 ) $ (9.1 ) $ 4.2 Prior service credit (11.3 ) (1.0 ) (13.9 ) (1.4 ) Total accumulated other comprehensive (income) loss $ (22.5 ) $ (4.8 ) $ (23.0 ) $ 2.8 The pre-tax amounts recognized in other comprehensive (income) loss, including noncontrolling interest, are as follows at September 30 (in millions): Postretirement Plans 2018 2017 2016 Net actuarial (gain) loss arising during period $ (9.7 ) $ 14.7 $ (1.4 ) Amortization and settlement recognition of net actuarial (loss) gain (0.3 ) 1.3 1.9 Prior service credit arising during period (1.5 ) (4.4 ) (3.8 ) Amortization or curtailment recognition of prior service credit 4.4 4.5 2.1 Net other comprehensive (income) loss recognized $ (7.1 ) $ 16.1 $ (1.2 ) The net periodic postretirement cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Postretirement Plans 2018 2017 2016 Service cost $ 1.5 $ 0.9 $ 2.3 Interest cost 7.9 7.4 8.1 Amortization of net actuarial loss (gain) 0.3 (1.3 ) (2.0 ) Amortization of prior service credit (4.4 ) (4.5 ) (2.1 ) Curtailment gain (0.1 ) (0.3 ) — Net postretirement cost $ 5.2 $ 2.2 $ 6.3 The assumed health care cost trend rates used in measuring the accumulated postretirement benefit obligation (“ APBO U.S. Plans Health care cost trend rate assumed for next year 6.03 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.43 % Year the rate reaches the ultimate trend rate 2037 Non-U.S. Plans Health care cost trend rate assumed for next year 5.51 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.51 % Year the rate reaches the ultimate trend rate 2018 As of September 30, 2018, the effect of a 1% change in the assumed health care cost trend rate would increase the APBO by approximately $7 million or decrease the APBO by approximately $6 million, and would increase the annual net periodic postretirement benefit cost for fiscal 2018 by $0 million or decrease the annual net periodic postretirement benefit cost for fiscal 2018 by approximately $1 million. Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Postretirement Plans 2018 2017 2016 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.09 % 6.51 % 4.04 % 6.64 % 4.70 % 6.84 % Rate of compensation increase N/A 7.37 % N/A 3.14 % N/A 3.10 % The estimated gains that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2019 are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Actuarial gain $ (1.1 ) $ (0.4 ) Prior service credit (2.6 ) (0.2 ) Total $ (3.7 ) $ (0.6 ) Our projected estimated benefit payments (unaudited), which reflect expected future service, as appropriate, are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Fiscal 2019 $ 9.3 $ 2.9 Fiscal 2020 $ 8.2 $ 3.0 Fiscal 2021 $ 7.8 $ 3.1 Fiscal 2022 $ 7.4 $ 3.2 Fiscal 2023 $ 7.1 $ 3.3 Fiscal Years 2024 – 2028 $ 31.4 $ 19.1 Multiemployer Plans We participate in several MEPPs that provide retirement benefits to certain union employees in accordance with various CBAs. The risks of participating in MEPPs are different from the risks of participating in single-employer pension plans. These risks include: • assets contributed to a MEPP by one employer are used to provide benefits to employees of all participating employers, • if a participating employer withdraws from a MEPP, the unfunded obligations of the MEPP allocable to such withdrawing employer may be borne by the remaining participating employers, and • if we withdraw from a MEPP, we may be required to pay that plan an amount based on our allocable share of the unfunded vested benefits of the plan, referred to as a withdrawal liability, as well as a share of the MEPP’s accumulated funding deficiency. Our contributions to a particular MEPP are established by the applicable CBAs; however, our required contributions may increase based on the funded status of a MEPP and legal requirements, such as those set forth in the Pension Act, which requires substantially underfunded MEPPs to implement a FIP or a RP to improve their funded status. Factors that could impact the funded status of a MEPP include, without limitation, investment performance, changes in participant demographics, decline in the number of contributing employers, changes in actuarial assumptions and the utilization of extended amortization provisions. We believe that certain of the MEPPs in which we participate or have participated, including the PIUMPF, have material unfunded vested benefits. The Pension Act established three categories, or “zones”, for the funded status of plans. Among other factors, plans in the green zone are at least 80% funded and are designated as healthy, plans in the yellow zone are greater than 65% but less than 80% funded and are designated as endangered and plans in the red zone are generally less than 65% funded and are designated as critical or critical and declining. Each plan’s actuary must certify the plan status annually. Several of the MEPPs in which we participate or have participated, including PIUMPF, have been certified in the red zone for critical and declining. Our share of the contributions in PIUMPF have exceeded 5% of total plan contributions in recent plan years. A FIP or RP requires a particular MEPP to adopt measures to correct its underfunded status. These measures may include, but are not limited to, an increase in our contribution rate from that provided in the applicable CBA, a reallocation of the contributions already being made by participating employers for various benefits to individuals participating in the MEPP, and/or a reduction in the benefits to be paid to future and/or current retirees. In addition, the Pension Act requires that a 5% surcharge be levied on employer contributions for the first year commencing shortly after the date the employer receives notice that the MEPP is certified in the red zone and a 10% surcharge on each succeeding year until a CBA is in place with terms and conditions consistent with the RP. On January 1, 2016, the surcharge we paid for PIUMPF increased from 10% to 15%. In the normal course of business, we evaluate our potential exposure to MEPPs, including with respect to potential withdrawal liabilities. During fiscal 2018, we submitted formal notification to withdraw from PIUMPF and recorded an estimated withdrawal liability of $180.0 million. The estimated withdrawal liability assumes payment over 20 years, discounted at a credit adjusted risk-free rate of 3.83%. We expect PIUMPF’s demand related to the withdrawal to include both a payment for withdrawal liability and for our proportionate share of PIUMPF’s accumulated funding deficiency. We reserve the right to challenge any portion of the demand, including any portion related to the accumulated funding deficiency. The estimated withdrawal liability noted above excludes the potential impact of a future mass withdrawal of other employers from PIUMPF, which is not considered probable or reasonably estimable at this time. Due to the absence of specific information regarding matters such as PIUMPF’s current financial situation, our estimate is subject to revision. In addition, in fiscal 2018, we submitted formal notification to withdraw from Central States and recorded an estimated withdrawal liability of $4.2 million on a discounted basis. It is reasonably possible that we may incur withdrawal liabilities with respect to certain other MEPPs in connection with such withdrawals. Our estimate of any such withdrawal liability, both individually and in the aggregate, is not material for the remaining plans in which we participate. At September 30, 2018 and September 30, 2017, we had withdrawal liabilities recorded of $247.8 million and $60.1 million, respectively. In addition to the contributions presented in the table below, for fiscal 2018, 2017 and 2016 we accrued $6.0 million, $1.9 million and $2.1 million, respectively, related to withdrawal liabilities. The impact of future withdrawal liabilities, future funding obligations or increased contributions may be material to our results of operations, cash flows and financial condition a

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 5. Income Taxes The components of income (loss) from continuing operations before income taxes are as follows (in millions): Year Ended September 30, 2018 2017 2016 United States $ 736.7 $ 481.9 $ (25.1 ) Foreign 298.1 375.7 269.7 Income from continuing operations before income taxes $ 1,034.8 $ 857.6 $ 244.6 The loss from continuing operations in the U.S. in fiscal 2016 was primarily the result of the pension risk transfer expense and restructuring charges. See “ Note 4. Retirement Plans Note 3. Restructuring and Other Costs Impacts of the Tax Act On December 22, 2017, the Tax Act was signed into law. The Tax Act contains significant changes to corporate taxation, including (i) the reduction of the corporate income tax rate to 21%, (ii) the acceleration of expensing for certain business assets, (iii) the one-time transition tax related to the transition of U.S. international tax from a worldwide tax system to a territorial tax system, (iv) the repeal of the domestic production deduction, (v) additional limitations on the deductibility of interest expense and (vi) expanded limitations on executive compensation. U.S. Securities and Exchange Commission Staff Accounting Bulletin (“ SAB The key impacts of the Tax Act on our financial statements for fiscal 2018 were the remeasurement of deferred tax balances to the new corporate tax rate and the accrual for the one-time transition tax liability. We recorded provisional amounts of the effects of the Tax Act. In order to calculate the effects of the new corporate tax rate on our deferred tax balances, ASC 740, “ Income Taxes Additionally, in fiscal 2018, we made a reasonable estimate for the amount of the one-time transition tax. The one-time transition tax is based on our total post-1986 foreign earnings and profits that were previously deferred from U.S. income tax. The applicable tax rate is based on the amount of those post-1986 earnings that is held in cash and other specified assets. We recorded a provisional one-time transition tax liability of $95.4 million or $87.1 million net of the release of a previously recorded outside basis difference. To date, we have been unable to determine a reasonable estimate of the tax liability, if any, under the Tax Act for our remaining outside basis difference or evaluate how the Tax Act will affect our existing accounting position to indefinitely reinvest unremitted foreign earnings. We will continue to apply our existing accounting under ASC 740 for this matter and finalize it in fiscal 2019. Our accounting for the income tax effects of the Tax Act will be completed during the measurement period allowed under SAB 118. We will record any necessary adjustments in the period such adjustments are identified. The final determination of the Tax Act will be made based on a variety of factors, among others, (i) further guidance from the U.S. Department of Treasury and from Securities Commission or FASB related to the Tax Act, (ii) management’s further assessment of the Tax Act and related regulatory guidance, and (iii) and changes to estimates made to calculate our existing temporary differences. As part of the enacted Tax Act, Global Intangible Low Taxed Income (“ GILTI Income tax expense (benefit) from continuing operations consists of the following components (in millions): Year Ended September 30, 2018 2017 2016 Current income taxes: Federal $ 83.0 $ 80.8 $ 98.3 State 26.8 3.3 12.8 Foreign 86.6 95.3 87.0 Total current expense 196.4 179.4 198.1 Deferred income taxes: Federal (1,108.6 ) 15.2 (131.5 ) State 53.2 (22.8 ) 6.9 Foreign (15.5 ) (12.8 ) 16.3 Total deferred (benefit) expense (1,070.9 ) (20.4 ) (108.3 ) Total income tax (benefit) expense $ (874.5 ) $ 159.0 $ 89.8 The differences between the statutory federal income tax rate and our effective income tax rate from continuing operations are as follows: Year Ended September 30, 2018 2017 2016 Statutory federal tax rate 24.5 % 35.0 % 35.0 % Foreign rate differential 0.6 (4.9 ) (5.5 ) Adjustment and resolution of federal, state and foreign tax uncertainties 0.9 (0.3 ) 0.2 State taxes, net of federal benefit 4.3 3.3 4.9 Tax Act (1) (109.1 ) — — Excess tax benefit related to stock compensation (0.8 ) — — Research and development and other tax credits, net of valuation allowances and reserves (0.5 ) (0.8 ) (6.1 ) Income attributable to noncontrolling interest (0.1 ) 0.4 0.8 Domestic manufacturer’s deduction (1.8 ) (2.0 ) (4.4 ) Sale of HH&B — (5.0 ) — U.S. legal entity restructuring — (3.3 ) — Change in valuation allowance (1.8 ) (3.3 ) 6.3 Nondeductible transaction costs — 1.0 0.4 Contribution of assets to Grupo Gondi joint venture — — 3.4 Nontaxable increased cash surrender value (0.8 ) (1.5 ) (4.6 ) Withholding taxes 0.5 0.4 2.0 Brazilian net worth deduction (0.9 ) (0.8 ) (2.0 ) Other, net 0.5 0.3 6.3 Effective tax rate (84.5 )% 18.5 % 36.7 % (1) The primary components are a $1,215.9 million benefit from the remeasurement of our net U.S. deferred tax liability and a one-time transition tax liability of $95.4 million or $87.1 million net of the release of a previously recorded outside basis difference. The tax effects of temporary differences that give rise to deferred income tax assets and liabilities consist of the following (in millions): September 30, 2018 2017 Deferred income tax assets: Accruals and allowances $ 22.1 $ 40.6 Employee related accruals and allowances 213.2 265.1 State net operating loss carryforwards 78.4 70.6 State credit carryforwards, net of federal benefit 64.8 54.4 U.S. and foreign tax credit carryforwards 14.7 135.9 Federal and foreign net operating loss carryforwards 188.7 204.1 Restricted stock and options 46.7 81.0 Other 45.3 32.8 Total 673.9 884.5 Deferred income tax liabilities: Property, plant and equipment 1,509.7 2,154.1 Deductible intangibles and goodwill 698.1 1,091.4 Inventory reserves 168.6 236.1 Deferred gain 258.8 405.2 Pension obligations 60.1 90.8 Basis difference in joint ventures 35.5 57.1 Other — 8.3 Total 2,730.8 4,043.0 Valuation allowances 229.4 219.1 Net deferred income tax liability $ 2,286.3 $ 3,377.6 Deferred taxes are recorded as follows in the consolidated balance sheet (in millions): September 30, 2018 2017 Long-term deferred tax asset (1) $ 35.2 $ 32.6 Long-term deferred tax liability 2,321.5 3,410.2 Net deferred income tax liability $ 2,286.3 $ 3,377.6 (1) The long-term deferred tax asset is presented in Other assets on the consolidated balance sheets. At September 30, 2018 and September 30, 2017, we had gross federal net operating losses of approximately $13.3 million and $61.2 million, respectively. These loss carryforwards generally expire between fiscal 2031 and 2038. At September 30, 2018 and September 30, 2017, we had alternative minimum tax credits of $14.7 million and $132.2 million, respectively. Under current tax law, the alternative minimum tax credit carryforwards become refundable tax credits in future years. We had no At September 30, 2018 and September 30, 2017, we had gross state and local net operating losses, of approximately $1,676 million and $1,885 million, respectively. These loss carryforwards generally expire between fiscal 2020 and 2038. The tax effected values of these net operating losses are $78.4 million and $70.6 million at September 30, 2018 and 2017, respectively, exclusive of valuation allowances of $7.8 million and $15.9 million at September 30, 2018 and 2017, respectively. At September 30, 2018 and September 30, 2017, gross net operating losses for foreign reporting purposes of approximately $698.4 million and $ 673.7 million, respectively, were available for carryforward. A majority of these loss carryforwards generally expire between fiscal 2020 and 2038, while a portion have an indefinite carryforward. The tax effected values of these net operating losses are $185.8 million and $182.6 million at September 30, 2018 and 2017, respectively, exclusive of valuation allowances of $161.5 million and $149.6 million at September 30, 2018 and 2017, respectively. At September 30, 2018 and 2017, we had state tax credit carryforwards of $64.8 million and $54.4 million, respectively. These state tax credit carryforwards generally expire within 5 to 10 years; however, certain state credits can be carried forward indefinitely. Valuation allowances of $56.1 million and $47.3 million at September 30, 2018 and 2017, respectively, have been provided on these assets. These valuation allowances have been recorded due to uncertainty regarding our ability to generate sufficient taxable income in the appropriate taxing jurisdiction. The following table represents a summary of the valuation allowances against deferred tax assets for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 219.1 $ 177.2 $ 100.2 Increases 50.8 54.3 24.8 Allowances related to purchase accounting (1) 0.1 12.4 63.0 Reductions (40.6 ) (24.8 ) (10.8 ) Balance at end of fiscal year $ 229.4 $ 219.1 $ 177.2 (1) Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition. Consistent with prior years, we consider a portion of our earnings from certain foreign subsidiaries as subject to repatriation and we provide for taxes accordingly. However, we consider the unremitted earnings and all other outside basis differences from all other foreign subsidiaries to be indefinitely reinvested. Accordingly, we have not provided for any taxes that would be due. As of September 30, 2018, we estimate our outside basis difference in foreign subsidiaries that are considered indefinitely reinvested to be approximately $1.5 billion. The components of the outside basis difference are comprised of purchase accounting adjustments, undistributed earnings, and equity components. Except for the portion of our earnings from certain foreign subsidiaries where we provided for taxes, we have not provided for any taxes that would be due upon the reversal of the outside basis differences. However, in the event of a distribution in the form of dividends or dispositions of the subsidiaries, we may be subject to incremental U.S. income taxes, subject to an adjustment for foreign tax credits, and withholding taxes or income taxes payable to the foreign jurisdictions. As of September 30, 2018, the determination of the amount of unrecognized deferred tax liability related to any remaining undistributed foreign earnings not subject to the Transition Tax and additional outside basis differences is not practicable. A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 148.9 $ 166.8 $ 106.6 Additions related to purchase accounting (1) 3.4 7.7 16.5 Additions for tax positions taken in current year 3.1 5.0 30.3 Additions for tax positions taken in prior fiscal years 18.0 15.2 20.6 Reductions for tax positions taken in prior fiscal years (5.3 ) (25.6 ) (9.7 ) Reductions due to settlement (2) (29.4 ) (14.1 ) (1.3 ) (Reductions) additions for currency translation adjustments (9.6 ) 2.0 7.0 Reductions as a result of a lapse of the applicable statute of limitations (2.0 ) (8.1 ) (3.2 ) Balance at end of fiscal year $ 127.1 $ 148.9 $ 166.8 (1) Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition. (2) Amounts in fiscal 2018 relate to the settlement of state audit examinations and federal and state amended returns filed related to affirmative adjustments for which a there was a reserve. Amounts in fiscal 2017 relate to the settlement of federal and state audit examinations with taxing authorities. As of September 30, 2018 and 2017, the total amount of unrecognized tax benefits was approximately $127.1 million and $148.9 million, respectively, exclusive of interest and penalties. Of these balances, as of September 30, 2018 and 2017, if we were to prevail on all unrecognized tax benefits recorded, approximately $108.7 million and $138.0 million, respectively, would benefit the effective tax rate. We regularly evaluate, assess and adjust the related liabilities in light of changing facts and circumstances, which could cause the effective tax rate to fluctuate from period to period. We recognize estimated interest and penalties related to unrecognized tax benefits in income tax expense in the consolidated statements of operations. As of September 30, 2018, we had liabilities of $70.4 million related to estimated interest and penalties for unrecognized tax benefits. As of September 30, 2017, we had liabilities of $81.7 million, net of indirect benefits, related to estimated interest and penalties for unrecognized tax benefits. Our results of operations for the fiscal year ended September 30, 2018, 2017 and 2016 include expense of $5.8 million, $7.4 million and $2.9 million, respectively, net of indirect benefits, related to estimated interest and penalties with respect to the liability for unrecognized tax benefits. As of September 30, 2018, it is reasonably possible that our unrecognized tax benefits will decrease by up to $5.5 million in the next twelve months due to expiration of various statues of limitations and settlement of issues. We file federal, state and local income tax returns in the U.S. and various foreign jurisdictions. With few exceptions, we are no longer subject to U.S. federal and state and local income tax examinations by tax authorities for years prior to fiscal 2015 and fiscal 2008, respectively. We are no longer subject to non-U.S. income tax examinations by tax authorities for years prior to fiscal 2011, except for Brazil for which we are not subject to tax examinations for years prior to 2005. While we believe our tax positions are appropriate, they are subject to audit or other modifications and there can be no assurance that any modifications will not materially and adversely affect our results of operations, financial condition or cash flows.

Segment Information

Segment Information	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Note 6. Segment Information We report our financial results of operations in the following three reportable segments: Corrugated Packaging, which consists of our containerboard mill and corrugated packaging operations, as well as our recycling operations; Consumer Packaging, which consists of consumer mills, folding carton, beverage, merchandising displays and partition operations; and Land and Development, which sells real estate primarily in the Charleston, SC region. Following the Combination and until the completion of the Separation, our financial results of operations had a fourth reportable segment, Specialty Chemicals. Prior to the HH&B Sale, our Consumer Packaging segment included HH&B. Certain income and expenses are not allocated to our segments and, thus, the information that management uses to make operating decisions and assess performance does not reflect such amounts. Items not allocated are reported as non-allocated expenses or in other line items in the table below after segment income. Some of our operations included in the segments are located in locations such as Canada, Mexico, South America, Europe, Asia and Australia. The table below reflects financial data of our foreign operations for each of the past three fiscal years, some of which were transacted in U.S. dollars (in millions, except percentages): Years Ended September 30, 2018 2017 2016 Foreign net sales to unaffiliated customers $ 3,236.7 $ 2,621.2 $ 2,426.6 Foreign segment income $ 360.7 $ 260.1 $ 226.1 Foreign long-lived assets $ 1,400.2 $ 1,558.3 $ 1,341.5 Foreign operations as a percent of consolidated operations: Foreign net sales to unaffiliated customers 19.9 % 17.6 % 17.1 % Foreign segment income 21.4 % 21.8 % 18.4 % Foreign long-lived assets 15.4 % 17.1 % 14.4 % We evaluate performance and allocate resources based, in part, on profit from operations before income taxes, interest and other items. The accounting policies of the reportable segments are the same as those described in “ Note 1. Description of Business and Summary of Significant Accounting Policies The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2018 2017 2016 Net sales (aggregate): Corrugated Packaging $ 9,103.4 $ 8,408.3 $ 7,868.5 Consumer Packaging 7,291.4 6,452.5 6,388.1 Land and Development 142.4 243.8 119.8 Total $ 16,537.2 $ 15,104.6 $ 14,376.4 Less net sales (intersegment): Corrugated Packaging $ 161.6 $ 155.8 $ 136.2 Consumer Packaging 90.5 89.1 68.4 Total $ 252.1 $ 244.9 $ 204.6 Net sales (unaffiliated customers): Corrugated Packaging $ 8,941.8 $ 8,252.5 $ 7,732.3 Consumer Packaging 7,200.9 6,363.4 6,319.7 Land and Development 142.4 243.8 119.8 Total $ 16,285.1 $ 14,859.7 $ 14,171.8 Segment income: Corrugated Packaging $ 1,207.9 $ 753.9 $ 739.9 Consumer Packaging 454.6 425.8 481.7 Land and Development 22.5 13.8 4.6 Segment income 1,685.0 1,193.5 1,226.2 Multiemployer pension withdrawals (184.2 ) — — Pension risk transfer expense — — (370.7 ) Pension lump sum settlement — (32.6 ) — Land and Development impairments (31.9 ) (46.7 ) — Restructuring and other costs (105.4 ) (196.7 ) (366.4 ) Non-allocated expenses (47.5 ) (43.5 ) (49.1 ) Interest expense, net (293.8 ) (222.5 ) (212.5 ) Gain on extinguishment of debt (0.1 ) 1.8 2.7 Other income, net 12.7 11.5 14.4 Gain on sale of HH&B — 192.8 — Income from continuing operations before income taxes $ 1,034.8 $ 857.6 $ 244.6 Segment income in fiscal 2018, 2017 and 2016 was reduced by $1.0 million, $26.5 million and $8.1 million, respectively, of expense for inventory stepped-up in purchase accounting, net of related LIFO impact. Corrugated Packaging segment income in fiscal 2018 was reduced by $1.0 million. Corrugated Packaging segment income and Consumer Packaging segment income in fiscal 2017 were reduced by $1.4 million and $25.1 million, respectively. The Corrugated Packaging segment income and Consumer Packaging segment income in fiscal 2016 were reduced by $3.4 million and $4.7 million, respectively. In fiscal 2019, we plan to operate our recycling operations primarily as a procurement function, shifting its focus to the procurement of low cost, high quality fiber for our mill system. As a result, we will no longer record recycling sales. The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2018 2017 2016 Identifiable assets: Corrugated Packaging $ 10,678.5 $ 10,537.7 $ 10,046.0 Consumer Packaging 11,902.2 11,877.8 10,122.5 Land and Development 49.1 89.8 460.6 Assets held for sale 59.5 173.6 52.3 Corporate 2,671.2 2,410.1 2,356.8 Total $ 25,360.5 $ 25,089.0 $ 23,038.2 Goodwill: Corrugated Packaging $ 1,890.9 $ 1,865.7 $ 1,722.5 Consumer Packaging 3,686.7 3,662.6 3,055.6 Total $ 5,577.6 $ 5,528.3 $ 4,778.1 Depreciation and amortization: Corrugated Packaging $ 676.8 $ 597.9 $ 576.2 Consumer Packaging 569.3 508.2 498.9 Land and Development 0.7 0.7 1.4 Discontinued operations — — 57.2 Corporate 5.4 5.3 8.2 Total $ 1,252.2 $ 1,112.1 $ 1,141.9 Capital expenditures: Corrugated Packaging $ 647.8 $ 492.1 $ 490.1 Consumer Packaging 317.8 265.8 244.9 Discontinued operations — — 45.2 Corporate 34.3 20.7 16.5 Total $ 999.9 $ 778.6 $ 796.7 Investment in unconsolidated entities: Corrugated Packaging $ 435.7 $ 321.1 $ 281.2 Consumer Packaging 21.7 24.7 22.2 Land and Development — 14.4 28.6 Corporate 0.4 0.4 (3.1 ) Total $ 457.8 $ 360.6 $ 328.9 The Corrugated Packaging segment’s investment in unconsolidated entities primarily relate to the Grupo Gondi investment. The Corporate investment in unconsolidated entities in fiscal 2016 primarily represented an entity that had losses that were guaranteed equally by the partners; this subsidiary has since been sold. The investment in Grupo Gondi that is included in the Corrugated Packaging segment’s investment in unconsolidated entities in fiscal 2018 and 2017 exceeds our proportionate share of the underlying equity in net assets by approximately $133.9 million and $76.2 million, respectively. Approximately $62.1 million and $59.2 million remains amortizable to expense in equity in income of unconsolidated entities over the estimated life of the underlying assets ranging from 10 to 15 years beginning with our investment in fiscal 2016. See “ Note 2. Mergers, Acquisitions and Investment The changes in the carrying amount of goodwill for the fiscal years ended September 30, 2018, 2017 and 2016 are as follows (in millions): Corrugated Packaging Consumer Packaging Total Balance as of October 1, 2015 Goodwill $ 1,667.5 $ 3,022.4 $ 4,689.9 Accumulated impairment losses — (42.8 ) (42.8 ) 1,667.5 2,979.6 4,647.1 Goodwill acquired 52.4 8.0 60.4 Goodwill disposed of (24.0 ) — (24.0 ) Purchase price allocation adjustments (4.9 ) 67.6 62.7 Translation adjustments 31.5 0.4 31.9 Balance as of September 30, 2016 Goodwill 1,722.5 3,098.4 4,820.9 Accumulated impairment losses — (42.8 ) (42.8 ) 1,722.5 3,055.6 4,778.1 Goodwill acquired 137.6 907.8 1,045.4 Goodwill disposed of — (329.6 ) (329.6 ) Purchase price allocation adjustments (1.2 ) 9.3 8.1 Translation adjustments 6.8 19.5 26.3 Balance as of September 30, 2017 Goodwill 1,865.7 3,705.4 5,571.1 Accumulated impairment losses — (42.8 ) (42.8 ) 1,865.7 3,662.6 5,528.3 Goodwill acquired 65.4 23.8 89.2 Goodwill disposed of (4.2 ) — (4.2 ) Purchase price allocation adjustments 2.3 18.4 20.7 Translation adjustments (38.3 ) (18.1 ) (56.4 ) Balance as of September 30, 2018 Goodwill 1,890.9 3,729.5 5,620.4 Accumulated impairment losses — (42.8 ) (42.8 ) $ 1,890.9 $ 3,686.7 $ 5,577.6 The goodwill acquired in fiscal 2018 primarily related to the Plymouth Packaging Acquisition in the Corrugated Packaging segment and the Schlüter Acquisition in the Consumer Packaging segment. The purchase price adjustments to goodwill in fiscal 2018 primarily related to the MPS Acquisition and the Hannapak Acquisition. The goodwill acquired in fiscal 2017 related to the MPS Acquisition and the Hannapak Acquisition in the Consumer Packaging segment and the U.S. Corrugated Acquisition, the Island Container Acquisition and the Star Pizza Acquisition in the Corrugated Packaging segment. The goodwill disposed of in the Corrugated Packaging segment in fiscal 2018 related to the sale of our solid waste management brokerage services business. The goodwill disposed of in the Consumer Packaging segment in fiscal 2017 was primarily related to the HH&B Sale. The goodwill acquired in fiscal 2016 related to the SP Fiber Acquisition and the Packaging Acquisition in the Corrugated Packaging and Consumer Packaging segments, respectively. The goodwill disposed of in the Corrugated Packaging segment in fiscal 2016 relates to the disposal of a portion of the reporting unit in connection with the investment in the Grupo Gondi unconsolidated joint venture. See “ Note 2. Mergers, Acquisitions and Investment

Discontinued Operations

Discontinued Operations	12 Months Ended
	Sep. 30, 2018
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations	Note 7. Discontinued Operations On May 15, 2016, WestRock completed the Separation. We distributed 100% of the outstanding common stock, par value $0.01 per share, of Ingevity, then a wholly-owned subsidiary of WestRock, to WestRock’s stockholders of record as of the close of business on May 4, 2016, with such stockholders receiving one share of Ingevity common stock for every six shares of Common Stock held as of such record date. Since the Separation, we have not beneficially owned any shares of Ingevity common stock and Ingevity has been an independent public company trading under the symbol “NGVT” on the NYSE. We disposed of the former Specialty Chemicals segment in its entirety and ceased to consolidate its assets, liabilities and results of operations. Accordingly, we have presented the financial position and results of operations of our former Specialty Chemicals segment as discontinued operations in the accompanying consolidated financial statements for all periods presented. In connection with the Separation, we and Ingevity entered into a separation and distribution agreement as well as various other agreements that provide a framework for the relationships between the parties going forward, including among others a tax matters agreement, a lease and ground service agreement with respect to our Covington, Virginia facility, an intellectual property agreement, a crude tall oil and black liquor soap skimming supply agreement, a trust agreement, an employee matters agreement and a transition service agreement. These agreements provided for the allocation between us and Ingevity of assets, employees, liabilities and obligations attributable to periods prior to, at and after the Separation and govern certain relationships between us and Ingevity after the Separation. Prior to the Separation, Ingevity, then a wholly-owned subsidiary of WestRock, borrowed $500.0 million in contemplation of the Separation and distributed the majority of these funds to WestRock, which used the funds to pay down debt. In addition, Ingevity assumed an $80.0 million, 7.67% capital lease obligation due January 15, 2027 owed to the City of Wickliffe, KY. In contemplation of the Separation, Ingevity also funded a trust in the amount of $68.9 million to secure the balloon principal payment of the capital lease upon the lease’s maturity. We remain a co-obligor on the capital lease obligation; therefore, the capital lease assumed by Ingevity remains recorded in our consolidated financial statements in long-term debt. At the time of the Separation, we recorded a $108.2 million long-term asset for the estimated fair value of the future principal and interest payments on the capital lease obligation assumed by Ingevity. The value of the long-term asset and the long-term debt under the lease will reduce over the life of the lease using the effective interest method. The $500.0 million of debt and the $68.9 million in the trust were assumed by Ingevity, and removed from our consolidated financial statements as part of our discontinued operations reporting. The following table presents the financial results of Specialty Chemicals’ discontinued operations (in millions): 2016 Net sales $ 533.7 Cost of goods sold 387.5 Selling, general and administrative, excluding intangible amortization 65.6 Selling, general and administrative intangible amortization 28.8 Restructuring and other costs 49.5 Impairment of Specialty Chemicals goodwill and intangibles 579.4 Operating loss (577.1 ) Interest income (expense) and other income (expense), net 0.1 Loss from discontinued operations before income taxes (577.0 ) Income tax benefit 32.3 Loss from discontinued operations $ (544.7 ) Fiscal 2016 restructuring and other costs are primarily associated with costs incurred to support the Separation and consist primarily of advisory, legal, accounting and other professional fees. Additionally, restructuring and other costs include $10.0 million of costs associated with the closure of Ingevity’s Duque de Caxias facility in Brazil and other severance and share-based compensation expenses. In the first quarter of fiscal 2016, as part of our evaluation of whether events or changes in circumstances had occurred that would indicate whether it was more likely than not that the goodwill of our then-owned Specialty Chemicals reporting unit was impaired, we considered factors such as, but not limited to, macroeconomic conditions, industry and market considerations, and financial performance, including the planned revenue and earnings of the reporting unit. We concluded that an impairment indicator had occurred related to the goodwill of the Specialty Chemicals reporting unit and that the indicator was driven by market factors subsequent to the Combination. Accordingly, we performed a “Step 1” goodwill impairment test where we updated the discounted cash flow analysis used to determine the reporting unit’s initial fair value on July 1, 2015. We also compared those results to the valuations performed by our investment bankers in connection with the planned separation of our Specialty Chemicals business. Based on the results of the impairment test and analysis, we concluded that the fair value of the Specialty Chemicals reporting unit was less than its carrying amount and began a “Step 2” goodwill impairment test to determine the amount of impairment loss, if any. As part of the analysis, we determined that the carrying value of the property, plant and equipment and intangibles, all of which have finite lives, on a “held and used” basis did not exceed the estimated undiscounted future cash flows. In light of changing market conditions, expected revenue and earnings of the reporting unit, lower comparative market valuations for companies in Specialty Chemicals’ peer group and our preliminary “Step 2” test, we concluded that an impairment of the Specialty Chemicals reporting unit was probable and could be reasonably estimated. As a result, we recorded a pre-tax and after-tax non-cash goodwill impairment charge of $478.3 million. This amount is included in the line item “Loss from discontinued operations” in the consolidated statements of operations. No tax benefit was recorded for the goodwill impairment. Until the completion of the Separation, GAAP required us to assess impairment of the Specialty Chemicals’ long-lived assets using the “held and used” model which was based on undiscounted future cash flows. Under this model, if the expected cash flows over the life of the primary asset of the reporting unit were in excess of the carrying amount, then there would be no impairment. At the date of the Separation, we assessed Specialty Chemical’s assets for potential impairment using the “held for sale” model. This model compares the fair value of the disposal unit to its carrying value and if the fair value less cost to sell is lower, then an impairment loss would be recorded. At the date of the Separation, we evaluated the Specialty Chemical’s intangibles, which consisted predominantly of customer list intangibles, for impairment. Our analysis at May 15, 2016, using the income approach (multi-period excess earnings method), indicated that there was a $101.1 million pre-tax non-cash impairment of our Specialty Chemicals customer relationships intangible. The impairment loss was recorded on the Separation and is included as a component of discontinued operations. The following table presents the significant non-cash items and capital expenditures for Specialty Chemicals’ that are included in the consolidated statements of cash flows (in millions): 2016 Depreciation, depletion and amortization $ 57.2 Impairment of Specialty Chemicals goodwill and intangibles $ 579.4 Capital expenditures $ (45.2 ) Depreciation expense and amortization expense in fiscal 2016 were $30.4 million $26.8 million, respectively.

Inventories

Inventories	12 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Inventories	Note 8. Inventories Inventories are as follows (in millions): September 30, 2018 2017 Finished goods and work in process $ 867.0 $ 905.0 Raw materials 730.0 614.2 Supplies and spare parts 368.2 360.7 Inventories at FIFO cost 1,965.2 1,879.9 LIFO reserve (135.6 ) (82.6 ) Net inventories $ 1,829.6 $ 1,797.3 It is impracticable to segregate the LIFO reserve between raw materials, finished goods and work in process. In fiscal 2018 and 2016, we reduced inventory quantities in some of our LIFO pools. These reductions result in liquidations of LIFO inventory quantities generally carried at lower costs prevailing in prior years as compared with the cost of the purchases in the respective fiscal years, the effect of which typically decreases cost of goods sold. The impact of the liquidations in fiscal 2018 and 2016 was not significant. In fiscal 2017, we had no LIFO layer liquidations.

Assets Held For Sale

Assets Held For Sale	12 Months Ended
	Sep. 30, 2018
Assets Held For Sale [Abstract]
Assets Held for Sale	Note 9. Assets Held For Sale Due to the accelerated monetization strategy, our Land and Development portfolio has met the held for sale criteria and is reflected as assets held for sale. Assets held for sale at September 30, 2018 of $59.5 million include $33.5 million of Land and Development portfolio assets, with the remainder primarily related to closed facilities. Assets held for sale at September 30, 2017 of $173.6 million include $150.4 million of Land and Development portfolio assets, with the remainder primarily related to closed facilities.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	Note 10. Property, Plant and Equipment Property, plant and equipment consists of the following (in millions): September 30, 2018 2017 Property, plant and equipment at cost: Land and buildings $ 2,078.9 $ 2,034.3 Machinery and equipment 12,064.0 11,349.7 Forestlands and mineral rights 158.0 208.3 Transportation equipment 30.1 30.7 Leasehold improvements 88.9 59.5 14,419.9 13,682.5 Less: accumulated depreciation, depletion and amortization (5,337.4 ) (4,564.2 ) Property, plant and equipment, net $ 9,082.5 $ 9,118.3 Depreciation expense, excluding discontinued operations, for fiscal 2018, 2017 and 2016 was $923.8 million, $855.9 million and $848.9 million, respectively. For depreciation expense related to our discontinued operations see “ Note 7. Discontinued Operations

Other Intangible Assets

Other Intangible Assets	12 Months Ended
	Sep. 30, 2018
Other Intangible Assets [Abstract]
Other Intangible Assets	Note 11. Other Intangible Assets The gross carrying amount and accumulated amortization relating to intangible assets, excluding goodwill, is as follows (in millions, except weighted avg. life): September 30, 2018 2017 Weighted Avg. Life (in years) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships 16.7 $ 4,123.7 $ (1,079.8 ) $ 4,046.2 $ (806.0 ) Favorable contracts 10.1 47.8 (34.8 ) 48.2 (30.7 ) Technology and patents 10.7 41.2 (18.0 ) 31.8 (14.4 ) Trademarks and tradenames 19.8 77.6 (43.9 ) 74.7 (31.4 ) Non-compete agreements 2.0 3.4 (1.7 ) 2.5 (0.6 ) License costs 9.6 24.6 (18.1 ) 23.6 (14.6 ) Total 16.6 $ 4,318.3 $ (1,196.3 ) $ 4,227.0 $ (897.7 ) Estimated intangible asset amortization expense for the succeeding five fiscal years is as follows (in millions): Fiscal 2019 $ 300.1 Fiscal 2020 $ 289.6 Fiscal 2021 $ 243.8 Fiscal 2022 $ 234.6 Fiscal 2023 $ 226.4 Intangible amortization expense, excluding discontinued operations, was $300.8 million, $234.0 million and $212.4 million during fiscal 2018, 2017 and 2016, respectively. We had other intangible amortization expense, primarily for packaging equipment leased to customers of $27.6 million, $22.2 million and $23.4 million during fiscal 2018, 2017 and 2016. For amortization expense related to our discontinued operations see “ Note 7. Discontinued Operations

Fair Value

Fair Value	12 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value	Note 12. Fair Value Assets and Liabilities Measured or Disclosed at Fair Value We estimate fair values in accordance with ASC 820 “Fair Value Measurement”. ASC 820 provides a framework for measuring fair value and expands disclosures required about fair value measurements. Specifically, ASC 820 sets forth a definition of fair value and a hierarchy prioritizing the inputs to valuation techniques. ASC 820 defines fair value as the price that would be received from the sale of an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Additionally, ASC 820 defines levels within the hierarchy based on the availability of quoted prices for identical items in active markets, similar items in active or inactive markets and valuation techniques using observable and unobservable inputs. We incorporate credit valuation adjustments to reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in our fair value measurements. We disclose the fair value of our long-term debt in “ Note 13. Debt Note 4. Retirement Plans Note 1 — Description of Business and Summary of Significant Accounting Policies — Fair Value of Financial Instruments and Nonfinancial Assets and Liabilities Accounts Receivable Sales Agreement We had an agreement (the “ A/R Sales Agreement ”) On September 25, 2018 we entered into a $550.0 million agreement (the “ New A/R Sales Agreement ”) Transfers and Servicing Note 13. Debt The following table represents a summary of the activity under the A/R Sales Agreement and the New A/R Sales Agreement for fiscal 2018 and 2017 (in millions): 2018 2017 Receivable from financial institution at beginning of fiscal year $ 24.9 $ 13.8 Receivables sold to the financial institution and derecognized 1,664.0 1,542.5 Receivables collected by financial institution (1,573.8 ) (1,466.7 ) Cash proceeds from financial institution (115.1 ) (64.7 ) Receivable from financial institution at September 30, $ — $ 24.9 Cash proceeds related to the receivables sold are included in cash from operating activities in the consolidated statement of cash flows in the accounts receivable line item. The expense recorded in connection with the sale is currently approximately $11 million per year and is recorded in “other income, net”. The future amount may fluctuate based on the level of activity and other factors. Although the sales are made without recourse, we maintain continuing involvement with the sold receivables as we provide collections services related to the transferred assets. The associated servicing liability is not material given the high quality of the customers underlying the receivables and the anticipated short collection period. Financial Instruments not Recognized at Fair Value Financial instruments not recognized at fair value on a recurring or nonrecurring basis include cash and cash equivalents, accounts receivable, certain other current assets, short-term debt, accounts payable, certain other current liabilities and long-term debt. With the exception of long-term debt, the carrying amounts of these financial instruments approximate their fair values due to their short maturities. See “ Note 13. Debt Fair Value of Nonfinancial Assets and Nonfinancial Liabilities We measure certain nonfinancial assets and nonfinancial liabilities at fair value on a nonrecurring basis. These assets and liabilities include cost and equity method investments when they are deemed to be other-than-temporarily impaired, assets acquired and liabilities assumed in an acquisition or in a nonmonetary exchange, and property, plant and equipment and intangible assets that are written down to fair value when they are held for sale or determined to be impaired. During fiscal 2018, 2017 and 2016, we did not have any significant nonfinancial assets or nonfinancial liabilities that were measured at fair value on a nonrecurring basis in periods subsequent to initial recognition other than the following pre-tax non-cash impairments: (i) the $31.9 million impairment of certain mineral rights and real estate in fiscal 2018, (ii) the $46.7 million real estate impairment recorded in fiscal 2017, (iii) a $17.6 million write-down of a customer relationship intangible in fiscal 2017 related to an exited product line, and (iv) the goodwill and intangible impairments in our former Specialty Chemicals segment in fiscal 2016. We discuss the former Specialty Chemicals impairments in “ Note 7. Discontinued Operations

Debt

Debt	12 Months Ended
	Sep. 30, 2018
Debt [Abstract]
Debt	Note 13. Debt The public bonds issued by WestRock RKT Company and WestRock MWV, LLC are guaranteed by WestRock and have cross-guarantees between the two companies. The industrial development bonds associated with the capital lease obligations of WestRock MWV, LLC are guaranteed by WestRock. The public bonds are unsecured, unsubordinated obligations that rank equally in right of payment with all of our existing and future unsecured, unsubordinated obligations. The bonds are effectively subordinated to any of our existing and future secured debt to the extent of the value of the assets securing such debt. At September 30, 2018, our Credit Facility, Farm Loan Credit Facility, European Revolving Credit Facility, Delayed Draw Credit Facilities, Commercial Paper Program, Other Revolving Credit Facilities (each as defined below) and public bonds were unsecured. The following were individual components of debt (in millions, except percentages): September 30, 2018 September 30, 2017 Carrying Value Weighted Avg Interest Rate Carrying Value Weighted Avg Interest Rate Public bonds due fiscal 2019 to 2022 $ 1,470.9 4.2 % $ 1,484.5 4.2 % Public bonds due fiscal 2023 to 2028 2,534.4 3.8 % 1,368.8 3.6 % Public bonds due fiscal 2030 to 2033 964.1 5.2 % 975.5 5.2 % Public bonds due fiscal 2037 to 2047 178.5 6.3 % 178.8 6.3 % Term loan facilities 599.4 3.7 % 1,622.7 2.5 % Revolving credit and swing facilities 355.0 3.2 % 436.4 1.1 % Receivables-backed financing facility — N/A 110.0 2.1 % Capital lease obligations 171.0 4.1 % 177.0 4.3 % Supplier financing and commercial card programs 105.1 N/A 130.3 N/A International and other debt 36.8 6.1 % 70.8 6.8 % Total debt 6,415.2 4.1 % 6,554.8 3.6 % Less: current portion of debt 740.7 608.7 Long-term debt due after one year $ 5,674.5 $ 5,946.1 A portion of the debt classified as long-term, may be paid down earlier than scheduled at our discretion without penalty. Certain customary restrictive covenants govern our maximum availability under our credit facilities. We test and report our compliance with these covenants as required and were in compliance with all of our covenants at September 30, 2018. The carrying value of our debt includes the fair value step-up of debt acquired in mergers and acquisitions. At September 30, 2018, the unamortized fair market value step-up was $250.8 million, which will be amortized over a weighted average remaining life of 12.3 years. The weighted average interest rate also includes the fair value step up. Excluding the step-up, the weighted average interest rate on total debt was 4.6%. At September 30, 2018, we had $104.9 million of outstanding letters of credit not drawn upon. At September 30, 2018, we had approximately $3.2 billion of availability under our committed credit facilities. This liquidity may be used to provide for ongoing working capital needs and for other general corporate purposes including acquisitions, dividends and stock repurchases. The estimated fair value of our debt was approximately $6.4 billion and $6.8 billion as of September 30, 2018 and September 30, 2017, respectively. The fair value of our long-term debt is categorized as level 2 within the fair value hierarchy and is primarily either based on quoted prices for those or similar instruments, or approximately the carrying amount, as the variable interest rates reprice frequently at observable current market rates. During fiscal 2018, 2017 and 2016, amortization of debt issuance costs charged to interest expense were $6.3 million, $4.5 million and $4.6 million, respectively. Public Bonds / Notes Issued At September 30, 2018 and September 30, 2017, the face value of our public bond obligations outstanding were $4.9 billion and $3.8 billion, respectively. On March 6, 2018, we issued $600.0 million aggregate principal amount of 3.75% senior notes due 2025 and $600.0 million aggregate principal amount of 4.0% senior notes due 2028 (collectively, the “ Notes On August 24, 2017, we issued $500.0 million aggregate principal amount of 3.0% Senior Notes due September 15, 2024 and $500.0 million aggregate principal amount of 3.375% Senior Notes due September 15, 2027 in an unregistered offering pursuant to Rule 144A and Regulation S under the Securities Act at a discount of approximately $1.4 million and $0.2 million, respectively, and recorded debt issuance costs of $4.2 million and $4.3 million, respectively, which are being amortized over the respective terms of the notes. Giving effect to the amortization of the original issue discount and the debt issuance costs, the effective interest rates of the notes are 3.18% and 3.48%, respectively. The proceeds from the issuance of the notes was used to pre-pay $575.0 million of amortization payments through the maturity of our term loan and $415.0 million then outstanding on the Receivables Facility. Term Loan Facilities and Revolving Credit Facility In connection with the Combination, on July 1, 2015, we entered into a credit agreement (the “ Credit Agreement Credit Facility On July 1, 2016, we executed an option to extend the term of the 5-year senior unsecured revolving credit facility for one year beyond the original term. On June 30, 2017, we executed an option to extend the term of the facility for a second additional year. Approximately $1.9 billion of the original $2.0 billion aggregate committed principal amount has been extended to July 1, 2022, and the remainder will continue to mature on July 1, 2020. Up to $150 million under the revolving credit facility may be used for the issuance of letters of credit. In addition, up to $400 million of the revolving credit facility may be used to fund borrowings in non-U.S. dollar currencies including Canadian dollars, Euro and Pound Sterling. Additionally, we may request up to $200 million of the revolving credit facility to be allocated to a Mexican peso revolving credit facility. At September 30, 2018 and September 30, 2017, we had no amounts outstanding under the revolving credit facility. At our option, loans issued under the Credit Facility will bear interest at either the London Interbank Offered Rate (“ LIBOR The Credit Agreement contains usual and customary representations and warranties, and usual and customary affirmative and negative covenants, including: financial covenants (including maintenance of a maximum consolidated debt to capitalization ratio and a minimum consolidated interest coverage ratio, as defined in the Credit Agreement) and limitations on liens, additional indebtedness and asset sales and mergers. The Credit Agreement also contains usual and customary events of default, including: non-payment of principal, interest, fees and other amounts; material breach of a representation or warranty; default on other material debt; bankruptcy or insolvency; incurrence of certain material ERISA liabilities; material judgments; impairment of loan documentation; change of control; and material breach of obligations under securitization programs. On July 1, 2015, three WestRock wholly-owned subsidiaries, RockTenn CP, LLC, a Delaware limited liability company, Rock-Tenn Converting Company, a Georgia corporation, and MeadWestvaco Virginia Corporation, a Delaware corporation, as borrowers, entered into a credit agreement (the “ Farm Loan Credit Agreement Farm Loan Credit Facility European Revolving Credit Facility On May 15, 2017, we entered into a $600.0 million European revolving credit facility with Coöperatieve Rabobank U.A., New York Branch as the administrative agent for the syndicate of banks. This facility provided for a 364-day unsecured On April 27, 2018, we entered into a €500.0 million revolving credit facility with an incremental €100.0 million accordion feature with Coöperatieve Rabobank U.A., New York Branch as the administrative agent for the syndicate of banks (the “ European Revolving Credit Facility ”). This facility provides for a 3-year unsecured U.S. dollar, Euro and Sterling denominated borrowing of not more than 500.0 million and matures on April 27, 2021. This facility replaced the $600.0 million European Revolving Credit Facility as discussed above. At September 30, 2018, Other Revolving Credit Facilities On October 31, 2017, we entered into a credit agreement with Wells Fargo Bank, National Association, as administrative agent, providing for a 364-day senior unsecured revolving credit facility in an aggregate committed principal amount of $450.0 million. The proceeds of the credit facility may be used for working capital and for other general corporate purposes. The credit facility is unsecured and is guaranteed by WestRock RKT Company and WestRock MWV, LLC and Whiskey Holdco, Inc. At our option, loans issued under the credit facility will bear interest at either LIBOR or an alternate base rate, in each case plus an applicable interest rate margin. At September 30 On February 10, 2017, we renewed the term of our $200.0 million uncommitted and revolving line of credit with Sumitomo Mitsui Banking Corporation (the “ Sumitomo Credit Facility On March 2, 2017, we renewed our €100.0 million uncommitted and revolving line of credit with Cooperatieve Rabobank U.A., New York Branch. The facility is available in Euros only, and continues until terminated in writing by WestRock or the lender. At September 30, 2018, there were no amounts outstanding under this facility. At September 30, 2017 we had $118.1 million outstanding. Receivables-Backed Financing Facility On July 22, 2016, we entered into a $700.0 million sixth amended and restated receivables sale agreement with certain originators (the “ Receivables Facility Borrowing availability under this facility is based on the eligible underlying accounts receivable and compliance with certain covenants. The agreement governing the Receivables Facility contains restrictions, including, among others, on the creation of certain liens on the underlying collateral. We test and report our compliance with these covenants monthly; we were in compliance with all of these covenants at September 30, 2018. At September 30, 2018 and September 30, 2017, maximum available borrowings, excluding amounts outstanding under the Receivables Facility, were $571.0 million and $577.6 million, respectively. The carrying amount of accounts receivable collateralizing the maximum available borrowings at September 30, 2018 was approximately $887.0 million. We have continuing involvement with the underlying receivables as we provide credit and collections services pursuant to the Receivables Facility agreement. At September 30, 2018 there were no amounts outstanding under this facility and the carrying value at September 30, 2017 was $110.0 million. Commercial Paper Program On October 31, 2017, we established an unsecured commercial paper program, pursuant to which we may issue short-term, unsecured commercial paper notes in an aggregate principal amount at any time not to exceed $1.0 billion with up to 397-day maturities (the “ Commercial Paper Program Delayed Draw Credit Facilities On March 7, 2018, we entered into a credit agreement (the “ Delayed Draw Credit Agreement Delayed Draw Credit Facilities On November 2, 2018, in connection with the closing of the KapStone Acquisition we drew upon the facility in full. The proceeds of the Delayed Draw Credit Facilities and other sources of cash were used to pay the consideration for the KapStone Acquisition, to repay certain existing indebtedness of KapStone and to pay fees and expenses incurred in connection with the KapStone Acquisition. The Delayed Draw Credit Facilities are senior unsecured obligations of the Company, as borrower, and each of Holdco, WestRock RKT Company and WestRock MWV, LLC, respectively, as guarantors. At our option, loans issued under the Delayed Draw Credit Facilities will bear interest at a floating rate based on either LIBOR or an alternate base rate, in each case plus an applicable interest rate margin. The applicable interest rate margin will be 1.125% to 2.000% per annum for LIBOR rate loans and 0.125% to 1.000% per annum for alternate base rate loans, in each case depending on the Leverage Ratio (as defined in the credit agreement) or Holdco’s corporate credit ratings, whichever yields a lower applicable interest rate margin, at such time. In addition, we will be required to pay a commitment fee of 0.125% per annum to 0.300% per annum (depending on the Leverage Ratio or the Company’s corporate credit ratings, whichever yields a lower fee) on the unused term loan commitments, accruing from June 5, 2018 until the earlier of the funding of the loans under the Delayed Draw Credit Facilities or the Delayed Draw Termination Date. Loans under the Delayed Draw Credit Facilities may be prepaid at any time without premium. The credit agreement contains usual and customary representations and warranties, and usual and customary affirmative and negative covenants, including: financial covenants (including maintenance of a maximum consolidated debt to capitalization ratio and a minimum consolidated interest coverage ratio) and limitations on liens, additional subsidiary indebtedness and asset sales and mergers. The credit agreement also contains usual and customary events of default, including: non-payment of principal, interest, fees and other amounts; material breach of a representation or warranty; default on other material debt; bankruptcy or insolvency; incurrence of certain material ERISA liabilities; material judgments; impairment of loan documentation; change of control; and material breach of obligations under securitization programs. Capital Lease and Other Indebtedness The range of due dates on our capital lease obligations are primarily in fiscal 2027 to 2035. Our international debt is primarily in Europe, Brazil and India. As of September 30, 2018, the aggregate maturities of debt, excluding capital lease obligations, for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 726.6 Fiscal 2020 474.5 Fiscal 2021 350.3 Fiscal 2022 1,000.9 Fiscal 2023 350.1 Thereafter 3,136.6 Fair value of debt step-up, deferred financing costs and unamortized bond discounts 205.2 Total $ 6,244.2 As of September 30, 2018, the aggregate maturities of capital lease obligations for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 5.0 Fiscal 2020 4.2 Fiscal 2021 2.5 Fiscal 2022 2.1 Fiscal 2023 0.6 Thereafter 138.1 Fair value step-up 18.5 Total $ 171.0

Operating Leases

Operating Leases	12 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Operating Leases	Note 14. Operating Leases We lease certain manufacturing and warehousing facilities and equipment, primarily transportation equipment, and office space under various operating leases. Some leases contain escalation clauses and provisions for lease renewal. As of September 30, 2018, future minimum lease payments under all noncancelable operating leases for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 132.1 Fiscal 2020 112.0 Fiscal 2021 87.9 Fiscal 2022 66.8 Fiscal 2023 51.6 Thereafter 165.4 Total future minimum lease payments $ 615.8 Rental expense for the years ended September 30, 2018, 2017 and 2016 was approximately $243.7 million, $210.5 million and $199.3 million, respectively, including lease payments under cancelable leases and maintenance charges on transportation equipment.

Special Purpose Entities

Special Purpose Entities	12 Months Ended
	Sep. 30, 2018
Special Purpose Entities [Abstract]
Special Purpose Entities	Note 15. Special Purpose Entities Pursuant to a sale of certain large-tract forestlands in 2007, a special purpose entity MWV Timber Notes Holding, LLC (“ MWV TN Timber Note Using the Timber Note as collateral, MWV TN received $338.3 million in proceeds under a secured financing agreement with a bank. Under the terms of the agreement, the liability from this transaction is non-recourse to the Company and is payable from the Timber Note proceeds upon its maturity in October 2027. As a result, the Timber Note is not available to satisfy any obligations of WestRock. MWV TN can elect to prepay at any time the liability in whole or in part, however, given that the Timber Note is not prepayable, MWV TN expects to only repay the liability at maturity from the Timber Note proceeds. The Timber Note and the secured financing liability were fair valued on the opening balance sheet in connection with the Combination. As of September 30, 2018, the Timber Note was $366.0 million and is included within restricted assets held by special purpose entities on the consolidated balance sheet and the secured financing liability was $323.1 million and is included within non-recourse liabilities held by special purpose entities on the consolidated balance sheet. Pursuant to the sale of MWV’s remaining U.S. forestlands, which occurred on December 6, 2013, another special purpose entity MWV Timber Notes Holding Company II, LLC (“ MWV TN II Installment Note Using the Installment Note as collateral, MWV TN II received $774.0 million in proceeds under a secured financing agreement with a bank. Under the terms of the agreement, the liability from this transaction is non-recourse to WestRock and is payable from the Installment Note proceeds upon its maturity in December 2023. As a result, the Installment Note is not available to satisfy any obligations of WestRock. MWV TN II can elect to prepay, at any time, the liability in whole or in part, with sufficient notice, but would avail itself of this provision only in the event the Installment Note was prepaid in whole or in part. The secured financing agreement however requires a mandatory repayment, up to the amount of cash received, if the Installment Note is prepaid in whole or in part. The Installment Note and the secured financing liability were fair valued on the opening balance sheet in connection with the Combination. As of September 30, 2018, the Installment Note was $915.0 million and is included within restricted assets held by special purpose entities on the consolidated balance sheet and the secured financing liability was $830.6 million and is included within non-recourse liabilities held by special purpose entities on the consolidated balance sheet.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Note 16. Related Party Transactions We sell products to affiliated companies. Net sales to the affiliated companies for the fiscal years ended September 30, 2018, 2017 and 2016 were approximately $418.8 million, $423.6 million and $346.6 million, respectively. Accounts receivable due from the affiliated companies at September 30, 2018 and 2017 was $64.2 million and $65.1 million, respectively, and was included in accounts receivable on our consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2018
Commitments And Contingencies [Abstract]
Commitments and Contingencies	Note 17. Commitments and Contingencies Capital Additions Estimated costs for future purchases of fixed assets that we are obligated to purchase as of September 30, 2018, total approximately $203 million. Environmental and Other Matters Environmental compliance requirements are a significant factor affecting our business. We employ manufacturing processes that result in various discharges, emissions and wastes. These processes are subject to numerous federal, state, local and international environmental laws and regulations, as well as the requirements of environmental permits and similar authorizations issued by various governmental authorities. On January 31, 2013, the EPA published Boiler MACT. Boiler MACT required compliance by January 31, 2016 or by January 31, 2017 for those mills for which we obtained a prior compliance extension. All work required for our boilers to comply with the rule has been completed. On July 29, 2016, the U.S. Court of Appeals for the District of Columbia Circuit issued a ruling on the consolidated cases challenging Boiler MACT. The court vacated key portions of the rule, including emission limits for certain subcategories of solid fuel boilers, and remanded other issues to the EPA for further rulemaking. At this time, we cannot predict with certainty how this decision will impact our existing Boiler MACT strategies or whether we will incur additional costs to comply with any revised Boiler MACT standards. In addition to Boiler MACT, we are subject to a number of other federal, state, local and international environmental rules that may impact our business, including the National Ambient Air Quality Standards for nitrogen oxide, sulfur dioxide, fine particulate matter and ozone for facilities in the U.S. We are involved in various administrative proceedings relating to environmental matters that arise in the normal course of business, and we may become involved in similar matters in the future. Although the ultimate outcome of these proceedings cannot be predicted with certainty and we cannot at this time estimate any reasonably possible losses based on available information, we do not believe that the currently expected outcome of any environmental proceedings and claims that are pending or threatened against us will have a material adverse effect on our results of operations, financial condition or cash flows. CERCLA and Other Remediation Costs We face potential liability under federal, state, local and international laws as a result of releases, or threatened releases, of hazardous substances into the environment from various sites owned and operated by third parties at which Company-generated wastes have allegedly been deposited. Generators of hazardous substances sent to off-site disposal locations at which environmental problems exist, as well as the owners of those sites and certain other classes of persons, are liable for response costs for the investigation and remediation of such sites under CERCLA and analogous laws. While joint and several liability is authorized under CERCLA, liability is typically shared with other PRPs, and costs are commonly allocated according to relative amounts of waste deposited and other factors. In addition, certain of our current or former locations are being investigated or remediated under various environmental laws, including CERCLA. Based on information known to us and assumptions, we do not believe that the costs of these projects will have a material adverse effect on our results of operations, financial condition or cash flows. However, the discovery of contamination or the imposition of additional obligations, including natural resources damaged at these or other sites in the future could result in additional costs. On January 26, 2009, Smurfit-Stone and certain of its subsidiaries filed a voluntary petition for relief under Chapter 11 of the U.S. Bankruptcy Code. Smurfit-Stone’s Canadian subsidiaries also filed to reorganize in Canada. We believe that matters relating to previously identified third-party PRP sites and certain facilities formerly owned or operated by Smurfit-Stone have been satisfied by claims in the Smurfit-Stone bankruptcy proceedings. However, we may face additional liability for cleanup activity at sites that are not subject to the bankruptcy discharge, but are not currently identified. The final bankruptcy distributions were made in fiscal 2018. We believe that we can assert claims for indemnification pursuant to existing rights we have under purchase and other agreements in connection with certain remediation sites. In addition, we believe that we have insurance coverage, subject to applicable deductibles/retentions, policy limits and other conditions, for certain environmental matters. However, there can be no assurance that we will be successful with respect to any claim regarding these insurance or indemnification rights or that, if we are successful, any amounts paid pursuant to the insurance or indemnification rights will be sufficient to cover all our costs and expenses. We also cannot predict with certainty whether we will be required to perform remediation projects at other locations, and it is possible that our remediation requirements and costs could increase materially in the future and exceed current reserves. In addition, we cannot currently assess with certainty the impact that future changes in cleanup standards or federal, state As of September 30, 2018, we had $10.8 million reserved for environmental liabilities on an undiscounted basis, of which $6.7 million is included in other long-term liabilities and $4.1 million in other current liabilities, including amounts accrued in connection with environmental obligations relating to the manufacturing facilities that we have closed. We believe the liability for these matters was adequately reserved at September 30, 2018. Climate Change Certain jurisdictions in which we have manufacturing facilities or other investments have taken actions to address climate change. The EPA has issued the Clean Air Act permitting regulations applicable to certain facilities that emit GHG. The EPA also has promulgated a rule requiring certain industrial facilities that emit 25,000 metric tons or more of carbon dioxide equivalent per year to file an annual report of their emissions. While we have facilities subject to existing GHG permitting and reporting requirements, the impact of these requirements has not been material to date. Additionally, the EPA has been working on a set of interrelated rulemakings aimed at cutting carbon emissions from power plants. On August 3, 2015, the EPA issued the Clean Power Plan. On the same day, the EPA issued a second rule setting standards of performance for new, modified and reconstructed electric utility generating units. On February 9, 2016, the U.S. Supreme Court issued a stay halting implementation of the Clean Power Plan until the pending legal challenges to the rule are resolved. As directed by Executive Order, on April 4, 2017, the EPA issued a proposed rule announcing its intention to review the Clean Power Plan, and, if appropriate, initiate proceedings to suspend, revise or rescind it. A number of states subject to the Clean Power Plan have stopped working on their implementation strategies in response to the litigation and Executive Order; however, certain states where we operate manufacturing facilities have indicated their intention to continue their carbon reduction efforts. On August 21, 2018, the EPA proposed the ACE rule, which would establish emission guidelines for states to develop plans to address greenhouse gas emissions from existing coal-fired power plants. The ACE rule would replace the 2015 Clean Power Plan, which EPA has In addition to national efforts to regulate climate change, some U.S. states in which we have manufacturing operations are also taking measures to reduce GHG emissions, such as requiring GHG emissions reporting or developing regional cap-and trade programs. California has enacted a cap-and-trade program that took effect in 2012, and includes enforceable compliance obligations that began on January 1, 2013. In July 2017, California extended the cap-and-trade program to 2030. We do not have any manufacturing facilities that are subject to the cap-and-trade requirements in California; however, we are continuing to monitor the implementation of this program as well as proposed mandatory GHG reduction efforts in other states. Also, the Washington Department of Ecology has issued a final rule, known as the Clean Air Rule, which applies to GHGs from facilities that have average annual carbon dioxide equivalent emissions equal to or exceeding 100,000 metric tons/year. Energy intensive and trade exposed facilities, including our Tacoma, WA and Longview, WA (which we acquired through the KapStone Acquisition (as hereinafter defined)) mills, and transportation fuel importers are subject to regulation under this program. In September 2016, various groups filed lawsuits against the Washington Department of Ecology challenging the Clean Air Rule. In April 2018, the Thurston County Superior Court invalidated the Clean Air Rule, and the Washington Department of Ecology subsequently filed an appeal with the State Supreme Court. The Court has not yet decided whether to grant the appeal. Implementation of the Clean Air Rule has been stayed in the meantime. The Paris Agreement established a framework for reducing global GHG emissions. By signing the Paris Agreement, the U.S. made a non-binding commitment to reduce economy-wide GHG emissions by 26% to 28% below 2005 levels by 2025. Other countries in which we conduct business, including China, European Union member states and India, have set GHG reduction targets. The Paris Agreement became effective on November 4, 2016. Although a party to the agreement may not provide the required one-year notice of withdrawal until three years after the effective date, in June 2017, President Trump announced that the U.S. intended to withdraw from the Paris Agreement. The governors of New York, California’s system and Washington’s system subsequently announced their intent to form a “climate alliance” to coordinate a state response to climate change. At this time, it is not possible to determine how the Paris Agreement, or any potential U.S. commitments in lieu of those under the agreement, may impact U.S. industrial facilities, including our domestic operations. Several of our international facilities are located in countries that have already adopted GHG emissions trading schemes. For example, Quebec has become a member of the Western Climate Initiative, which is a collaboration among California and certain Canadian provinces that have joined together to create a cap-and-trade program to reduce GHG emissions. In 2009, Quebec adopted a target of reducing GHG emissions by 20% below 1990 levels by 2020 and 37.5% from 1990 levels by 2030. In 2011, Quebec issued a final regulation establishing a regional cap-and-trade program that required reductions in GHG emissions from covered emitters as of January 1, 2013. The Province formally linked its carbon trading system with California in January 2014 and with Ontario in January 2018. Our mill in Quebec is subject to these cap-and-trade requirements, although the direct impact of this regulation has not been material to date. Compliance with this program and other similar programs may require future expenditures to meet required GHG emission reduction requirements in future years. The regulation of climate change continues to develop in the areas of the world where we conduct business. We have systems in place for tracking the GHG emissions from our energy-intensive facilities, and we carefully monitor developments in climate change laws, regulations and policies to assess the potential impact of such developments on our results of operations, financial condition, cash flows and disclosure obligations. Litigation A lawsuit filed in the U.S. District Court of the Northern District of Illinois in 2010 alleges that certain named defendants violated the Sherman Act by conspiring to limit the supply and fix the prices of containerboard and products containing containerboard from February 15, 2004 through November 8, 2010 (the “ Antitrust Litigation We have been named a defendant in asbestos-related personal injury litigation. To date, the costs resulting from the litigation, including settlement costs, have not been significant. As of September 30 We are a defendant in a number of other lawsuits and claims arising out of the conduct of our business. While the ultimate results of such suits or other proceedings against us cannot be predicted with certainty, we believe the resolution of these other matters will not have a material adverse effect on our results of operations, financial condition or cash flows. Guarantees We make certain guarantees in the course of conducting our operations, for compliance with certain laws and regulations, or in connection with certain business dispositions. The guarantees include items such as funding of net losses in proportion to our ownership share of certain joint ventures, debt guarantees related to certain unconsolidated entities acquired in acquisitions, indemnifications of lessors in certain facilities and equipment operating leases for items such as additional taxes being assessed due to a change in tax law and certain other agreements. We estimate the exposure for these matters could be approximately $50 million. As of September 30, 2018, we have recorded $11.7 million for the estimated fair value of these guarantees. We are unable to estimate our maximum exposure under operating leases because it is dependent on potential changes in the tax laws; however, we believe our exposure related to guarantees would not have a material impact on our results of operations, financial condition or cash flows.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss)	12 Months Ended
	Sep. 30, 2018
Other Comprehensive Income Loss [Abstract]
Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss)	Note 18. Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss) The following table summarizes the changes in accumulated other comprehensive loss by component for the fiscal years ended September 30, 2018 and 2017 (in millions): Deferred Loss on Cash Flow Hedges Defined Benefit Pension and Postretirement Plans Foreign Currency Items Available for Sale Security Total (1) Balance at September 30, 2016 $ (0.2 ) $ (523.8 ) $ (102.4 ) $ — $ (626.4 ) Other comprehensive income before reclassifications — 22.8 80.8 0.7 104.3 Amounts reclassified from accumulated other comprehensive (income) loss (0.5 ) 35.6 — — 35.1 Sale of HH&B — 2.9 26.8 — 29.7 Net current period other comprehensive loss (income) (0.5 ) 61.3 107.6 0.7 169.1 Balance at September 30, 2017 $ (0.7 ) $ (462.5 ) $ 5.2 $ 0.7 $ (457.3 ) Other comprehensive (loss) income before reclassifications — (18.6 ) (234.4 ) 0.8 (252.2 ) Amounts reclassified from accumulated other comprehensive loss (income) 0.5 15.2 — (1.5 ) 14.2 Net current period other comprehensive income (loss) 0.5 (3.4 ) (234.4 ) (0.7 ) (238.0 ) Balance at September 30, 2018 $ (0.2 ) $ (465.9 ) $ (229.2 ) $ — $ (695.3 ) (1) All amounts are net of tax and noncontrolling interest. The following table summarizes the reclassifications out of accumulated other comprehensive loss by component for the fiscal years ended September 30, 2018 and 2017 (in millions): Years Ended September 30, 2018 2017 Pre-Tax Tax Net of Tax Pre-Tax Tax Net of Tax Amortization of defined benefit pension and postretirement items: (1) Actuarial gains (losses) (2) $ 20.9 (5.9 ) $ 15.0 $ (56.3 ) $ 20.4 $ (35.9 ) Prior service credits (2) 0.3 (0.1 ) 0.2 0.5 (0.2 ) 0.3 Sale of HH&B (3) — — — (4.2 ) 1.3 (2.9 ) Subtotal defined benefit plans 21.2 (6.0 ) 15.2 (60.0 ) 21.5 (38.5 ) Foreign currency translation adjustments: (1) Sale of HH&B (3) — — — (26.8 ) — (26.8 ) Available for sale security (4) (1.5 ) — (1.5 ) — — — Derivative Instruments: (1) Foreign currency cash flow hedges (4) 0.7 (0.2 ) 0.5 0.8 (0.3 ) 0.5 Total reclassifications for the period $ 20.4 $ (6.2 ) $ 14.2 $ (86.0 ) $ 21.2 $ (64.8 ) (1) Amounts in parentheses indicate charges to earnings. Amounts pertaining to noncontrolling interests are excluded. (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See “ Note 4. Retirement Plans (3) Included in gain on sale of HH&B. (4) These accumulated other comprehensive income components are included in net sales. A summary of the components of other comprehensive (loss) income, including noncontrolling interest, for the years ended September 30, 2018, 2017 and 2016, is as follows (in millions): Fiscal 2018 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (234.4 ) $ — $ (234.4 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 0.7 (0.2 ) 0.5 Net actuarial loss arising during period (29.0 ) 15.9 (13.1 ) Amortization and settlement recognition of net actuarial loss 20.9 (5.9 ) 15.0 Prior service cost arising during the period (7.8 ) 2.3 (5.5 ) Amortization of prior service cost 0.3 (0.1 ) 0.2 Unrealized gain on available for sale security 0.8 — 0.8 Reclassification adjustment of net gain on available for sale security included in earnings (1.5 ) — (1.5 ) Consolidated other comprehensive loss (250.0 ) 12.0 (238.0 ) Less: Other comprehensive income attributable to noncontrolling interests — — — Other comprehensive loss attributable to common stockholders $ (250.0 ) $ 12.0 $ (238.0 ) Fiscal 2017 Pre-Tax Tax Net of Tax Foreign currency translation gain $ 80.7 $ — $ 80.7 Sale of HH&B, foreign currency 26.8 — 26.8 Reclassification adjustment of net gain on cash flow hedges included in earnings (0.8 ) 0.3 (0.5 ) Net actuarial gain arising during period 34.1 (11.9 ) 22.2 Amortization and settlement recognition of net actuarial loss 56.4 (20.4 ) 36.0 Prior service credit arising during the period 1.0 (0.3 ) 0.7 Amortization of prior service credit (0.4 ) 0.2 (0.2 ) Unrealized gain on available for sale security 0.7 — 0.7 Sale of HH&B, defined benefit pension plans 4.2 (1.3 ) 2.9 Consolidated other comprehensive income 202.7 (33.4 ) 169.3 Less: Other comprehensive income attributable to noncontrolling interests (0.2 ) — (0.2 ) Other comprehensive income attributable to common stockholders $ 202.5 $ (33.4 ) $ 169.1 Fiscal 2016 Pre-Tax Tax Net of Tax Foreign currency translation gain $ 109.8 $ — $ 109.8 Deferred loss on cash flow hedges (0.7 ) 0.3 (0.4 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 1.9 (0.7 ) 1.2 Net actuarial loss arising during period (354.0 ) 129.4 (224.6 ) Amortization and settlement recognition of net actuarial loss (1) 379.7 (143.2 ) 236.5 Prior service credit arising during the period 2.3 (0.9 ) 1.4 Amortization of prior service cost 1.8 (0.7 ) 1.1 Sale of foreign subsidiary 20.2 — 20.2 Consolidated other comprehensive income 161.0 (15.8 ) 145.2 Less: Other comprehensive loss attributable to noncontrolling interests 0.7 — 0.7 Other comprehensive income attributable to common stockholders $ 161.7 $ (15.8 ) $ 145.9 (1) Includes pension risk transfer expense.

Stockholders_ Equity

Stockholders’ Equity	12 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders’ Equity	Note 19. Stockholders’ Equity Capitalization Our capital stock consists solely of Common Stock. Holders of our Common Stock are entitled to one vote per share. Our amended and restated certificate of incorporation also authorizes preferred stock, of which no shares have been issued. The terms and provisions of such shares will be determined by our board of directors upon any issuance of such shares in accordance with our certificate of incorporation. Stock Repurchase Plan In July 2015, our board of directors authorized a repurchase program of up to 40.0 million shares of our Common Stock, representing approximately 15% of our outstanding Common Stock as of July 1, 2015. The shares of our Common Stock may be repurchased over an indefinite period of time at the discretion of management. In fiscal 2018, we repurchased approximately 3.4 million shares of our Common Stock for an aggregate cost of $195.1 million. In fiscal 2017, we repurchased approximately 1.8 million shares of our Common Stock for an aggregate cost of $93.0 million. In fiscal 2016, we repurchased approximately 8.1 million shares of our Common Stock for an aggregate cost of $335.3 million. As of September 30, 2018, we had remaining authorization under the repurchase program authorized in July 2015 to purchase approximately 21.3 million shares of our Common Stock.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Sep. 30, 2018
Stock Based Compensation [Abstract]
Stock Based Compensation	Note 20. Share-Based Compensation Share-based Compensation Plans At our Annual Meeting of Stockholders held on February 2, 2016, our stockholders approved the WestRock Company 2016 Incentive Stock Plan. The 2016 Incentive Stock Plan was amended and restated on February 2, 2018 (the “ Amended and Restated 2016 Incentive Stock Plan The table below shows the approximate number of shares: available for issuance, available for future grant, to be issued if restricted awards granted with a performance condition recorded at target achieve the maximum award, and if new grants pursuant to the plan are expected to be issued, each as adjusted as necessary for corporate actions (in millions). Shares Available For Issuance Shares Available For Future Grant Shares To Be Issued If Performance Is Achieved At Maximum Expect To Make New Awards Amended and Restated 2016 Incentive Stock Plan (1) 11.7 8.0 2.5 Yes 2004 Incentive Stock Plan (1)(2) 15.8 3.1 0.0 No 2005 Performance Incentive Plan (1)(2) 12.8 9.0 0.0 No RockTenn (SSCC) Equity Inventive Plan (1)(3) 7.9 5.9 0.0 No (1) As part of the Separation, equity-based incentive awards were generally adjusted to maintain the intrinsic value of awards immediately prior to the Separation. The number of unvested restricted stock awards and unexercised stock options and SARs at the time of the Separation were increased by an exchange factor of approximately 1.12. In addition, the exercise price of unexercised stock options and SARs at the time of the Separation was converted to decrease the exercise price by an exchange factor of approximately 1.12. (2) In connection with the Combination, WestRock assumed all RockTenn and MWV equity incentive plans. We issued awards to certain key employees and our directors pursuant to our RockTenn 2004 Incentive Stock Plan, as amended, and our MWV 2005 Performance Incentive Plan, as amended. The awards were converted into WestRock awards using the conversion factor as described in Business Combination Agreement. (3) In connection with the Smurfit-Stone Acquisition, we assumed the Smurfit-Stone equity incentive plan, which was renamed the Rock-Tenn Company (SSCC) Equity Incentive Plan. The awards were converted into shares of RockTenn Common Stock, options and restricted stock units, as applicable, using the conversion factor as described in the merger agreement. Our results of operations for the fiscal years ended September 30, 2018, 2017 and 2016 include share-based compensation expense of $66.8 million, $60.9 million and $75.7 million, respectively, including $2.9 million included in the gain on sale of HH&B in fiscal 2017. Share-based compensation expense in fiscal 2017 was reduced by $5.4 million for the rescission of shares granted to our CEO that were inadvertently granted in excess of plan limits in fiscal 2014 and 2015. The total income tax benefit in the results of operations in connection with share-based compensation was $19.4 million, $22.5 million and $29.2 million, for the fiscal years ended September 30, 2018, 2017 and 2016, respectively. Cash received from share-based payment arrangements for the fiscal years ended September 30, 2018, 2017 and 2016 was $44.4 million, $59.2 million and $33.9 million, respectively. Equity Awards Issued in Connection with the MPS Acquisition In connection with the MPS Acquisition, we replaced certain outstanding awards of restricted stock units granted under the MPS long-term incentive plan with WestRock restricted stock units. No additional shares will be granted under the MPS plan. The MPS equity awards were replaced with identical terms utilizing an approximately 0.33 conversion factor as described in the merger agreement. As part of the MPS Acquisition, we granted 119,373 awards of restricted stock units, which contain service conditions and were valued at $54.24 per share. The acquisition consideration included approximately $1.9 million related to outstanding MPS equity awards related to service prior to the effective date of the MPS Acquisition – the balance related to service after the effective date will be expensed over the remaining service period of the awards. Stock Options and Stock Appreciation Rights Stock options granted under our plans generally have an exercise price equal to the closing market price on the date of the grant, generally vest in three years, in either one tranche or in approximately one-third increments, and have 10-year contractual terms. However, a portion of our grants are subject to earlier expense recognition due to retirement eligibility rules. Presently, other than circumstances such as death, disability and retirement, grants will include a provision requiring both a change of control and termination of employment to accelerate vesting. At the date of grant, we estimate the fair value of stock options granted using a Black-Scholes option pricing model. We use historical data to estimate option exercises and employee terminations in determining the expected term in years for stock options. Expected volatility is calculated based on the historical volatility of our stock, or a combination of the historical volatility of both RockTenn and MWV grants. The risk-free interest rate is based on U.S. Treasury securities in effect at the date of the grant of the stock options. The dividend yield is estimated based on our historic annual dividend payments and current expectations for the future. We did not grant any stock options in fiscal 2018 and 2017. We applied the following weighted average assumptions to estimate the fair value of stock option grants made in the following period: 2016 Expected term in years 7.0 Expected volatility 38.3 % Risk-free interest rate 1.6 % Dividend yield 4.5 % The table below summarizes the changes in all stock options during the fiscal year ended September 30, 2018: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2017 5,866,127 $ 30.51 Exercised (1,582,313 ) 21.73 Expired (5,819 ) 37.17 Forfeited (24,341 ) 32.13 Outstanding at September 30, 2018 4,253,654 $ 33.75 4.3 $ 85.8 Exercisable at September 30, 2018 3,845,523 $ 34.17 4.0 $ 76.1 Vested and expected to vest at September 30, 2018 4,251,748 $ 33.75 4.3 $ 85.7 The weighted average grant date fair value for options granted during the fiscal year ended September 30, 2016 was $8.06 per share. The aggregate intrinsic value of options exercised during the years ended September 30, 2018, 2017 and 2016 was $67.4 million, $54.3 million and $14.5 million, respectively. As of September 30, 2018, there was $0.4 million of total unrecognized compensation cost related to nonvested stock options; that cost is expected to be recognized over a weighted average remaining vesting period of 0.3 years. We amortize these costs on a straight-line basis over the explicit service period. As part of the Combination, we issued SARs to replace outstanding MWV SARs. The SARs were valued using the Black-Scholes option pricing model. We measure compensation expense related to the SAR awards at the end of each period. We do not expect to issue additional SARs. The table below summarizes the changes in all SARs during the fiscal year ended September 30, 2018: SARs Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2017 51,016 $ 25.30 Exercised (9,935 ) 16.66 Expired (4,095 ) 27.69 Outstanding at September 30, 2018 36,986 $ 27.36 2.4 $ 1.0 Exercisable at September 30, 2018 36,986 $ 27.36 2.4 $ 1.0 The aggregate intrinsic value of SARs exercised during the years ended September 30, 2018, 2017 and 2016 was $0.5 million, $0.4 million and $0.2 million, respectively. Restricted Stock Restricted stock is typically granted annually to non-employee directors and certain of our employees. Our non-employee director awards generally vest over a period of up to one year and are treated as issued and carry dividend and voting rights until they vest. The vesting provisions for our employee awards may vary from grant to grant; however, vesting generally is contingent upon meeting various service and/or performance or market goals including, but not limited to, achievement of various financial targets including Cash Flow Per Share, Cash Flow to Equity Ratio and relative Total Shareholder Return (each as defined in the award documents). Subject to the level of performance attained, the target award for some of the grants may increase up to 200% of target or decrease to zero depending upon the terms of the individual grant. The employee grants generally vest in three years. Presently, other than circumstances such as death, disability and retirement, the grants generally include a provision requiring both a change of control and termination of employment to accelerate vesting. For certain employee grants, the grantee is entitled to receive dividend equivalent units, but will generally forfeit the restricted award and the dividend equivalents if the employee separates from us during the vesting period or if the predetermined goals are not accomplished. The table below summarizes the changes in unvested restricted stock during the fiscal year ended September 30, 2018: Shares/Units Weighted Average Grant Date Fair Value Unvested at September 30, 2017 (1) 2,959,449 $ 45.28 Granted 1,116,111 69.36 Vested (697,717 ) 57.39 Forfeited (153,669 ) 45.07 Unvested at September 30, 2018 (1) 3,224,174 $ 51.01 (1) Target awards granted with a performance condition, net of subsequent forfeitures, may be increased up to 200% of the target or decreased to zero, subject to the level of performance attained. The awards are reflected in the table at the target award amount of 100%. Based on current facts and assumptions we are forecasting the performance of the grants to be attained at levels that would result in the issuance of approximately 0.9 million additional shares. However, it is possible that the performance attained may vary. There was approximately $83.5 million of unrecognized compensation cost related to all unvested restricted shares as of September 30, 2018 that will be recognized over a weighted average remaining vesting period of 1.3 years. The following table represents a summary of restricted stock shares granted in fiscal 2018, 2017 and 2016 with terms defined in the applicable grant letters. The shares are not deemed to be issued and carry voting rights until the relevant conditions defined in the award documents have been met, unless otherwise noted. 2018 2017 2016 Shares of restricted stock granted to non-employee directors (1) 23,285 26,521 64,155 Shares of restricted stock granted to employees: Shares granted for attainment of a performance condition at an amount in excess of target (2) 45,964 340,319 447,261 Shares granted with a service condition and a Cash Flow Per Share performance condition at target (3) (4) 432,655 507,070 1,211,760 Shares granted with a service condition and a relative Total Shareholder Return market condition at target (3) 259,695 301,980 — Shares granted with a service condition (5) 354,512 309,850 27,370 Share of restricted stock assumed in purchase accounting: Shares granted with a service condition (6) — 119,373 — Total restricted stock granted 1,116,111 1,605,113 1,750,546 (1) Non-employee director grants generally vest over a period of up to one year and are deemed issued on the grant date and have voting and dividend rights. (2) (3) These employee grants vest over approximately three years and have adjustable ranges from 0 - 200% of target subject to the level of performance attained in the respective award agreement. The employee grants with a relative Total Shareholder Return condition were valued using a Monte Carlo simulation, the terms of which are outlined below. (4) Shares granted in fiscal 2015 were reduced by 50,326 shares at target related to the rescission of shares granted to our CEO that were inadvertently granted in excess of plan limits. (5) These shares vest over approximately three to four years. (6) These shares vest over approximately one to three years. The employee grants with a relative Total Shareholder Return market condition in fiscal 2018 were valued using a Monte Carlo simulation at $66.28 per share. The significant assumptions used in valuing these grants included: an expected term of 2.9 years, an expected volatility of 29.7% and a risk-free interest rate of 2.3%. We amortize these costs on a straight-line basis over the explicit service period. The employee grants with a relative Total Shareholder Return market condition in fiscal 2017 were valued using a Monte Carlo simulation at $64.41 per share. The significant assumptions used in valuing these grants included: an expected term of 2.9 years, an expected volatility of 30.6% and a risk-free interest rate of 1.4%. We amortize these costs on a straight-line basis over the explicit service period. Expense is recognized on restricted stock grants on a straight-line basis over the explicit service period or for performance based grants over the explicit service period when we estimate that it is probable the performance conditions will be satisfied. Expense recognized on grants with a performance condition that affects how many shares are ultimately awarded is based on the number of shares expected to be awarded. The following table represents a summary of restricted stock vested in fiscal 2018, 2017 and 2016 (in millions, except shares): 2018 2017 2016 Shares of restricted stock vested 697,717 1,112,909 1,589,761 Aggregate fair value of restricted stock vested $ 46.1 $ 59.5 $ 57.5 The shares vested in fiscal 2018 reflect the vesting of the fiscal 2015 grants, with a Cash Flow Per Share performance condition that vested at 103.7% of target, as well as certain shares with a performance and/or service condition, including those shares assumed upon the Combination. The shares vested in 2017 reflect the vesting of the fiscal 2014 grant, with a Cash Flow Per Share performance condition that vested at 176.6% of target, certain shares assumed upon the Combination with a performance and/or service condition, as well as other awards accelerated in connection with the Combination for certain former employees. The shares vested in 2016 reflect the vesting of the fiscal 2013 grant, with a cash flow to equity ratio performance condition that vested at maximum, certain shares assumed upon the Combination with a performance and/or service condition, as well as other awards accelerated in connection with the Combination for certain former employees. Employee Stock Purchase Plan At our Annual Meeting of Stockholders held on February 2, 2016, our stockholders approved the WestRock Company Employee Stock Purchase Plan (“ ESPP

Earnings per Share

Earnings per Share	12 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Note 21. Earnings per Share Restricted stock awards we grant to non-employee directors are considered participating securities as they receive non-forfeitable rights to dividends at the same rate as our Common Stock. As participating securities, we include these instruments in the earnings allocation in computing earnings per share under the two-class method described in ASC 260, “ Earnings per Share. September 30, 2018 2017 2016 Numerator: Income from continuing operations $ 1,909.3 $ 698.6 $ 154.8 Less: Net (income) loss from continuing operations attributable to noncontrolling interest (3.2 ) 9.6 (2.1 ) Income available to common stockholders, before discontinued operations 1,906.1 708.2 152.7 Less: Distributed and undistributed income available to participating securities (0.2 ) (0.1 ) — Distributed and undistributed income attributable to common stockholders, before discontinued operations 1,905.9 708.1 152.7 Loss from discontinued operations (1) — — (549.0 ) Net income (loss) attributable to common stockholders $ 1,905.9 $ 708.1 $ (396.3 ) Denominator: Basic weighted average shares outstanding 255.5 252.2 254.0 Effect of dilutive stock options and non-participating securities 4.3 3.5 3.9 Diluted weighted average shares outstanding 259.8 255.7 257.9 Basic earnings per share from continuing operations $ 7.46 $ 2.81 $ 0.60 Basic loss per share from discontinued operations — — (2.16 ) Basic earnings (loss) per share attributable to common stockholders $ 7.46 $ 2.81 $ (1.56 ) Diluted earnings per share from continuing operations $ 7.34 $ 2.77 $ 0.59 Diluted loss per share from discontinued operations — — (2.13 ) Diluted earnings (loss) per share attributable to common stockholders $ 7.34 $ 2.77 $ (1.54 ) (1) Net of income attributable to noncontrolling interests of discontinued operations of $4.3 million for the fiscal year ended September 30, 2016. Weighted average shares include zero, 0.2 million and 0.3 million of reserved, but unissued shares at September 30, 2018, 2017 and 2016. These reserved shares were distributed as claims were liquidated or resolved in accordance with the resolution of Smurfit-Stone bankruptcy claims. The final bankruptcy distributions were made in fiscal 2018. Options and restricted stock in the amount of 0.2 million, 0.7 million and 1.6 million common shares in fiscal 2018, 2017 and 2016, respectively, were not included in computing diluted earnings per share because the effect would have been antidilutive. The dilutive impact of the remaining awards outstanding in each year were included in the effect of dilutive securities.

Financial Results by Quarter (U

Financial Results by Quarter (Unaudited)	12 Months Ended
	Sep. 30, 2018
Financial Results By Quarter Unaudited [Abstract]
Financial Results by Quarter	Note 22. Financial Results by Quarter (Unaudited) Fiscal 2018 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 3,894.0 $ 4,017.0 $ 4,137.5 $ 4,236.6 Cost of goods sold $ 3,111.6 $ 3,220.4 $ 3,264.3 $ 3,294.9 Multiemployer pension withdrawals $ 180.0 $ — $ 4.2 $ — Land and Development impairments $ 27.6 $ — $ 1.7 $ 2.6 Restructuring and other costs $ 16.3 $ 31.7 $ 17.1 $ 40.3 (Loss) gain on extinguishment of debt $ (1.0 ) $ 0.1 $ 0.9 $ (0.1 ) Income tax benefit (expense) $ 1,073.2 $ (18.8 ) $ (84.5 ) $ (95.4 ) Consolidated net income $ 1,133.5 $ 224.5 $ 271.3 $ 280.0 Net income attributable to common stockholders $ 1,135.1 $ 223.2 $ 268.2 $ 279.6 Basic earnings per share attributable to common stockholders $ 4.45 $ 0.87 $ 1.05 $ 1.10 Diluted earnings per share attributable to common stockholders $ 4.38 $ 0.86 $ 1.03 $ 1.08 Fiscal 2017 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 3,447.2 $ 3,656.3 $ 3,695.6 $ 4,060.6 Cost of goods sold $ 2,855.9 $ 2,980.9 $ 3,000.1 $ 3,282.6 Pension lump sum settlement $ — $ 28.7 $ — $ 3.9 Land and Development impairments $ — $ 42.7 $ — $ 4.0 Restructuring and other costs $ 81.0 $ 18.3 $ 59.4 $ 38.0 (Loss) gain on extinguishment of debt $ — $ (0.1 ) $ 2.0 $ (0.1 ) Gain on sale of HH&B $ — $ — $ 190.6 $ 2.2 Consolidated net income $ 78.5 $ 98.2 $ 326.6 $ 195.3 Net income attributable to common stockholders $ 80.9 $ 103.1 $ 328.1 $ 196.1 Basic earnings per share attributable to common stockholders $ 0.32 $ 0.41 $ 1.30 $ 0.77 Diluted earnings per share attributable to common stockholders $ 0.32 $ 0.40 $ 1.29 $ 0.76 We computed the interim earnings per common and common equivalent share amounts as if each quarter was a discrete period. As a result, the sum of the basic and diluted earnings per share by quarter will not necessarily total the annual basic and diluted earnings per share. Consolidated net income in the first quarter of fiscal 2018 financial results by quarter (unaudited) table was decreased as the result of recording an estimated multiemployer pension withdrawal of $180.0 million, or $179.1 million net of noncontrolling interest, to withdraw from a multiemployer pension plan. See “ Note 4. Retirement Plans — Multiemployer Plans Note 5. Income Taxes Consolidated net income in the second quarter of fiscal 2018 financial results by quarter (unaudited) table increased by $36.3 million related to an adjustment to the provisional amount previously recorded for the measurement of our deferred tax balances in connection with the Tax Act. Basic and diluted earnings per share attributable to common stockholders were each increased by $0.14 per share. Consolidated net income in the first quarter of fiscal 2017 financial results by quarter (unaudited) table was increased due to a $23.8 million tax benefit related to the reduction of a state deferred tax liability as a result of an internal U.S. legal entity restructuring that will simplify future operating activities within the U.S. Basic and diluted earnings per share attributable to common stockholders were each increased by approximately $0.09 per share. Consolidated net income in the second quarter of fiscal 2017 financial results by quarter (unaudited) table was decreased due to a non-cash charge of $28.7 million recorded on the line item “Pension lump sum settlement” on our Consolidated Statements of Operations related to our year to date lump sum payments to certain beneficiaries of the Plan, together with several one-time severance benefit payments out of the Plan, triggered pension settlement accounting. For additional information see “ Note 4. Retirement Plans ” Consolidated net income in the third quarter of fiscal 2017 financial results by quarter (unaudited) table was increased due to a pre-tax gain on sale of HH&B of $190.6 million. Basic and diluted earnings per share from continuing operations and basic and diluted earnings per share attributable to common stockholders were each increased by approximately $0.76 and $0.75 per share, respectively. See “ Note 1. Description of Business and Summary of Significant Accounting Policies — Description of Business ”

Subsequent Event

Subsequent Event	12 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Note 23. Subsequent Events (Unaudited) KapStone Acquisition On November 2, 2018, pursuant to the Merger Agreement, the Company acquired all of the outstanding shares of KapStone through the Mergers. KapStone is a leading North American producer and distributor of containerboard, corrugated products and specialty papers, including liner and medium containerboard, kraft papers and saturating kraft. KapStone also owns Victory Packaging, a packaging solutions distribution company with facilities in the United States, Canada and Mexico. As a result of the Mergers, among other things, the Company became the ultimate parent of WRKCo, KapStone and their respective subsidiaries. Effective as of the Effective Time, the Company changed its name to “WestRock Company” and WRKCo changed its name to “WRKCo Inc.”. Pursuant to the Merger Agreement, at the Effective Time (a) each issued and outstanding share of common stock, par value $0.01 per share, of WRKCo (“ WRKCo common stock KapStone common stock $35.00 per share 0.4981 25% The estimated consideration for the KapStone Acquisition was $4.8 billion including debt assumed and an estimate of equity awards to be replaced with WestRock equity awards with identical terms. As a result, KapStone stockholders received in the aggregate approximately $3.3 billion in cash and WestRock common stock, or approximately 0.6% of the issued and outstanding shares of WestRock common stock immediately following the Effective Time. Pursuant to the Merger Agreement, at the Effective Time, the Company assumed any outstanding awards granted under the equity-based incentive plans of WRKCo and KapStone (including the shares underlying such awards), the award agreements evidencing the grants of such awards and, in the case of the WRKCo equity-based incentive plans, the remaining shares available for issuance under the applicable plan, in each case subject to adjustments to such awards in the manner set forth in the Merger Agreement. Hurricane Damage In October 2018, our containerboard and pulp mill located in Panama City, FL sustained extensive damage from Hurricane Michael. We shut down the mill’s operations in advance of the hurricane’s landfall. In early November, the mill started producing linerboard and we expect to ramp up to full production by the end of November 2018. Our market pulp production line is expected to operate at 50% of capacity by early December 2018 and should return to full operation in approximately six months. While it is still too early to identify the full cost, we anticipate the total of our property damage and business interruption claim will be approximately $ million. We have property damage and business interruption insurance that will cover most of the cost of bringing the mill back to full operation. We have a $15 million deductible, and expect the majority of costs will be covered.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2018
Description Of Business And Summary Of Significant Accounting Policies [Abstract]
Consolidation	Consolidation The consolidated financial statements include our accounts and the accounts of our partially-owned consolidated subsidiaries. Equity investments in which we exercise significant influence but do not control and are not the primary beneficiary are accounted for using the equity method. Investments in which we are not able to exercise significant influence over the investee are accounted for under the cost method. Our equity and cost method investments are not significant either individually or in the aggregate. We have eliminated all significant intercompany accounts and transactions. See “ Note 6. Segment Information
Use of Estimates	Use of Estimates Preparing consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates, and the differences could be material. The most significant accounting estimates inherent in the preparation of our consolidated financial statements include estimates to evaluate the recoverability of goodwill, intangibles and property, plant and equipment, to determine the useful lives of assets that are amortized or depreciated, and to measure income taxes, self-insured obligations, restructuring activities and allocate the purchase price of an acquired business to the fair value of acquired assets and liabilities. In addition, significant estimates form the basis for our reserves with respect to collectability of accounts receivable, inventory valuations, pension benefits, deferred tax asset valuation allowances and certain benefits provided to current and retired employees. Various assumptions and other factors underlie the determination of these significant estimates. The process of determining significant estimates is fact specific and takes into account factors such as historical experience, current and expected economic conditions, product mix, and in some cases, actuarial techniques. We regularly evaluate these significant factors and make adjustments where facts and circumstances dictate.
Revenue Recognition	Revenue Recognition We recognize revenue when there is persuasive evidence that an arrangement exists, delivery has occurred or services have been rendered, our price to the buyer is fixed or determinable and collectability is reasonably assured. Delivery is not considered to have occurred until the customer takes title and assumes the risks and rewards of ownership. The timing of revenue recognition is dependent on the location of title transfer which is normally either on the exit from our plants (i.e., shipping point) or on arrival at customers’ plants (i.e., destination point). We do not recognize revenue from transactions where we bill customers, but retain custody and title to these products until the date custody and title transfer. We do not have any significant multiple deliverable revenue arrangements. We net, against our gross sales, provisions for discounts, returns, allowances, customer rebates and other adjustments. We account for such provisions during the same period in which we record the related revenues. We include in net sales any amounts related to shipping and handling that are billed to a customer. See “ Note 1. Description of Business and Summary of Significant Accounting Policies — New Accounting Standards — Recently Adopted ASU FASB ASC Revenue from Contracts with Customers
Shipping and Handling Cost	Shipping and Handling Costs We classify shipping and handling costs, such as freight to our customers’ destinations, as a component of cost of goods sold. When shipping and handling costs are included in the sales price charged for our products, they are recognized in net sales.
Cash and Cash Equivalents	Cash Equivalents We consider all highly liquid investments that mature three months or less from the date of purchase to be cash equivalents. The carrying amounts we report in the consolidated balance sheets for cash and cash equivalents approximate fair market values. We place our cash and cash equivalents with large credit worthy banks, which limits the amount of our credit exposure.
Accounts Receivables and Allownanes	Accounts Receivable and Allowances We derive our accounts receivable from revenue earned from customers located primarily in North America, South America, Europe, Asia and Australia. Given our diverse customer base, we have limited exposure to credit loss from any particular customer or industry segment, and hence we generally do not require collateral. We perform an evaluation of probable credit losses inherent in our accounts receivable at each balance sheet date. Such an evaluation includes consideration of historical loss experience, trends in customer payment frequency, present economic conditions, and judgment about the future financial health of our customers and industry sector. The weighted average of our receivables collection is within 30 to 60 days. We sell certain receivables under our New A/R Sales Agreement. We state accounts receivable at the amount owed by the customer, net of an allowance for estimated uncollectible accounts, returns and allowances, cash discounts and other adjustments. We do not discount accounts receivable because we generally collect accounts receivable over a relatively short time. We account for sales and other taxes that are imposed on and concurrent with individual revenue-producing transactions between a customer and us on a net basis which excludes the taxes from our net sales. We charge off receivables when they are determined to be no longer collectible. In fiscal 2018, 2017 and 2016 our bad debt expense was not significant. The following table represents a summary of the changes in the reserve for allowance for doubtful accounts, returns and allowances and cash discounts for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 45.8 $ 36.5 $ 29.5 Reduction in sales and charges to costs and expenses 202.8 215.6 200.8 Deductions (198.9 ) (206.3 ) (193.8 ) Balance at end of fiscal year $ 49.7 $ 45.8 $ 36.5
Inventories	Inventories We value substantially all U.S. inventories at the lower of cost or market, with cost determined on the LIFO basis. We value all other inventories at the lower of cost and net realizable value, with cost determined using methods that approximate cost computed on a first-in first-out inventory valuation method (“ FIFO Prior to the application of the LIFO method, our U.S. operating divisions use a variety of methods to estimate the FIFO cost of their finished goods inventories. Such methods include standard costs, or average costs computed by dividing the actual cost of goods manufactured by the tons produced and multiplying this amount by the tons of inventory on hand. Lastly, certain operations calculate a ratio, on a plant by plant basis, the numerator of which is the cost of goods sold and the denominator is net sales. This ratio is applied to the estimated sales value of the finished goods inventory. Variances and other unusual items are analyzed to determine whether it is appropriate to include those items in the value of inventory. Examples of variances and unusual items that are considered to be current period charges include, but are not limited to, abnormal production levels, freight, handling costs, and wasted materials (spoilage). Cost includes raw materials and supplies, direct labor, indirect labor related to the manufacturing process and depreciation and other factory overheads. Our inventoried spare parts are measured at average cost.
Property, Plant and Equipment	Property, Plant and Equipment We state property, plant and equipment at cost less accumulated depreciation. Cost includes major expenditures for improvements and replacements that extend useful lives, increase capacity, increase revenues or reduce costs, while normal maintenance and repairs are expensed as incurred. During fiscal 2018, 2017 and 2016, we capitalized interest of approximately $8.2 million, $7.0 million and $7.6 million, respectively. For financial reporting purposes, we provide depreciation and amortization primarily on a straight-line method generally over the estimated useful lives of the assets as follows: Buildings and building improvements 15-40 years Machinery and equipment 3-25 years Transportation equipment 3-8 years Generally, our machinery and equipment have estimated useful lives between 3 and 25 years; however, select portions of machinery and equipment primarily at our mills have estimated useful lives up to 44 years. Greater than 90% of the cost of our mill assets have lives of 25 years or less. Leasehold improvements are depreciated over the shorter of the asset life or the lease term, generally between 3 and 10 years.
Goodwill and Intangible Assets	Goodwill and Long-Lived Assets We review the carrying value of our goodwill annually at the beginning of the fourth quarter of each fiscal year, or more often if events or changes in circumstances indicate that the carrying amount may exceed fair value as set forth in ASC 350, “Intangibles — Goodwill and Other.” Note 7. Discontinued Operations The goodwill impairment model is a two-step process. An amendment to ASC 350 became effective December 2011 that allows a qualitative assessment, prior to step one, to determine whether it is more likely than not that the fair value of a reporting unit exceeds its carrying amount. We did not attempt a qualitative assessment and moved directly to step one. In step one, we utilize the present value of expected net cash flows or, as appropriate, a combination of the present value of expected net cash flows and the guideline public company method to determine the estimated fair value of our reporting units. This present value model requires management to estimate future net cash flows, the timing of these cash flows, and a discount rate (based on a weighted average cost of capital), which represents the time value of money and the inherent risk and uncertainty of the future cash flows. Factors that management must estimate when performing this step in the process include, among other items, sales volume, prices, inflation, discount rates, exchange rates, tax rates, anticipated synergies and productivity improvements resulting from acquisitions, capital expenditures and continuous improvement projects. The assumptions we use to estimate future cash flows are consistent with the assumptions that the reporting units use for internal planning purposes, updated to reflect current expectations. The guideline public company method involves comparing the reporting unit to similar companies whose stock is freely traded on an organized exchange. The fair values determined by the discounted cash flow and guideline public company methods were weighted to arrive at the concluded fair value of the reporting unit. However, in instances where comparisons to our peers is less meaningful, no weight was placed on the guideline public company method to arrive at the concluded fair value of the reporting unit. If we determine that the estimated fair value of the reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired. If we determine that the carrying amount of the reporting unit exceeds its estimated fair value, we would complete step two of the impairment analysis. Step two involves determining the implied fair value of the reporting unit’s goodwill and comparing it to the carrying amount of that goodwill. If the carrying amount of the reporting unit’s goodwill exceeds the implied fair value of that goodwill, we recognize an impairment loss in an amount equal to that excess. While ASU 2017-04, “ Simplifying the Test for Goodwill Impairment During the fourth quarter of fiscal 2018, of those reporting units that have goodwill, our Consumer Packaging reporting unit had a fair value which exceeded its carrying value by less than 10%, primarily due to the fair value accounting related to the Combination and the MPS Acquisition. If we had concluded that it was appropriate to increase the discount rate we used by 100 basis points to estimate the fair value of each reporting unit that has goodwill, the fair value of each of our reporting units would have continued to exceed its carrying value, except for the Consumer Packaging reporting unit. No events have occurred since the latest annual goodwill impairment assessment that would necessitate an interim goodwill impairment assessment. We follow the provisions included in ASC 360, “Property, Plant and Equipment” Included in our long-lived assets are certain identifiable intangible assets. These intangible assets are amortized based on the approximate pattern in which the economic benefits are consumed or straight-line if the pattern was not reliably determinable. Estimated useful lives range from 1 to 40 years and have a weighted average life of approximately 16.6 years. Our judgments regarding the existence of impairment indicators are based on legal factors, market conditions and operational performance. Future events could cause us to conclude that impairment indicators exist and that assets associated with a particular operation are impaired. Evaluating impairment also requires us to estimate future operating results and cash flows, which also require judgment by management. Any resulting impairment loss could have a material adverse impact on our financial condition and results of operations.
Restructuring and Other Costs	Restructuring and Other Costs Our restructuring and other costs include primarily items such as restructuring portions of our operations, acquisition costs, integration costs and divestiture costs. We have restructured portions of our operations from time to time, have current restructuring initiatives taking place, and it is possible that we may engage in future restructuring activities. Identifying and calculating the cost to exit these operations requires certain assumptions to be made, the most significant of which are anticipated future liabilities, including severance costs, leases and other contractual obligations, and the adjustment of property, plant and equipment to net realizable value. We believe our estimates are reasonable, considering our knowledge of the industries we operate in, previous experience in exiting activities and valuations we may obtain from independent third parties. Although our estimates have been reasonably accurate in the past, significant judgment is required, and these estimates and assumptions may change as additional information becomes available and facts or circumstances change. See “ Note 3. Restructuring and Other Costs
Business Combinations	Business Combinations From time to time, we may enter into business combinations. In accordance with ASC 805, “ Business Combinations Significant estimates and assumptions in estimating the fair value of acquired technology, customer relationships, and other identifiable intangible assets include future cash flows that we expect to generate from the acquired assets. If the subsequent actual results and updated projections of the underlying business activity change compared with the assumptions and projections used to develop these values, we could record impairment charges. In addition, we have estimated the economic lives of certain acquired assets and these lives are used to calculate depreciation and amortization expense. If our estimates of the economic lives change, depreciation or amortization expenses could be increased or decreased, or the acquired asset could be impaired.
Fair Value of Financial Instruments and Nonfinancial Assets and Liabilities	Fair Value of Financial Instruments and Nonfinancial Assets and Liabilities We estimate fair values in accordance with ASC 820, “Fair Value Measurement. Financial instruments not recognized at fair value on a recurring or nonrecurring basis include cash and cash equivalents, accounts receivables, certain other current assets, short-term debt, accounts payable, certain other current liabilities and long-term debt. With the exception of long-term debt, the carrying amounts of these financial instruments approximate their fair values due to their short maturities. The fair values of our long-term debt are estimated using quoted market prices or are based on the discounted value of future cash flows. We disclose the fair value of long-term debt in “ Note 13. Debt ” “ Note 4. Retirement Plans ” Supplemental Plans We measure certain nonfinancial assets and nonfinancial liabilities at fair value on a nonrecurring basis. These assets and liabilities include cost and equity method investments when they are deemed to be other-than-temporarily impaired, assets acquired and liabilities assumed in a merger or an acquisition or in a nonmonetary exchange, and property, plant and equipment and goodwill and other intangible assets that are written down to fair value when they are held for sale or determined to be impaired. Given the nature of nonfinancial assets and liabilities, evaluating their fair value from the perspective of a market participant is inherently complex. Assumptions and estimates about future values can be affected by a variety of internal and external factors. Changes in these factors may require us to revise our estimates and could result in future impairment charges for goodwill and acquired intangible assets, or retroactively adjust provisional amounts that we have recorded for the fair values of assets and liabilities in connection with business combinations. These adjustments could have a material impact on our financial condition and results of operations. We discuss fair values in more detail in “ Note 12. Fair Value ”.
Derivatives	Derivatives We are exposed to interest rate risk, commodity price risk and foreign currency exchange risk. To manage these risks, from time to time and to varying degrees, we may enter into a variety of financial derivative transactions and certain physical commodity transactions that are determined to be derivatives. Interest rate swaps may be entered into to manage the interest rate risk associated with a portion of our outstanding debt. Interest rate swaps are either designated for accounting purposes as cash flow hedges of forecasted floating interest payments on variable rate debt or fair value hedges of fixed rate debt, or we may elect not to treat them as accounting hedges. Swaps or forward contracts on certain commodities may be entered into to manage the price risk associated with forecasted purchases or sales of those commodities. In addition, certain commodity financial derivative contracts and physical commodity contracts that are determined to be derivatives may not be designated as accounting hedges because either they do not meet the criteria for treatment as accounting hedges under ASC 815, “Derivatives and Hedging”, Outstanding financial derivative instruments expose us to credit loss in the event of nonperformance by the counterparties to the derivative agreements. Our credit exposure related to these financial instruments is represented by the fair value of contracts reported as assets. We manage our exposure to counterparty credit risk through minimum credit standards, diversification of counterparties and procedures to monitor concentrations of credit risk. We may enter into financial derivative contracts that may contain credit-risk-related contingent features which could result in a counterparty requesting immediate payment or demanding immediate and ongoing full overnight collateralization on derivative instruments in net liability positions. For financial derivative instruments that are designated as a cash flow hedge for accounting purposes, the effective portion of the gain or loss on the financial derivative instrument is reported as a component of other comprehensive income and reclassified into earnings in the same line item associated with the forecasted transaction, and in the same period or periods during which the forecasted transaction affects earnings. Gains and losses on the financial derivative instrument representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current earnings. We have at times entered into interest rate swap agreements that effectively modified our exposure to interest rate risk by converting a portion of our interest payments on floating rate debt to a fixed rate basis, thus reducing the impact of interest rate changes on future interest expense. These agreements typically involved the receipt of floating rate amounts in exchange for fixed interest rate payments over the life of the agreements without an exchange of the underlying principal amount. At September 30, 2018, there were no interest rate or commodity derivatives outstanding, and the notional amount of foreign currency derivatives were $356.0 million. At September 30, 2017, there were no interest rate or commodity derivatives outstanding, and the notional amount of foreign currency derivatives were $47.8 million. For additional information see “ Note 13. Debt
Health Insurance	Health Insurance We are self-insured for the majority of our group health insurance costs. However, we seek to limit our health insurance costs by entering into certain stop loss insurance coverage. Due to mergers, acquisitions and other factors, we may have plans that do not include stop loss insurance. We calculate our group health insurance reserve on an undiscounted basis based on estimated reserve rates. We utilize claims lag data provided by our claims administrators to compute the required estimated reserve rate. We calculate our average monthly claims paid using the actual monthly payments during the trailing 12-month period. At that time, we also calculate our required reserve using the reserve rates discussed above. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our group health insurance costs.
Workers Compensation	Workers’ Compensation We purchase large risk deductible workers’ compensation policies for the majority of our workers’ compensation liabilities that are subject to various deductibles to limit our exposure. We calculate our workers’ compensation reserves on an undiscounted basis based on estimated actuarially calculated development factors. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our workers' compensation costs.
Income Taxes	Income Taxes We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amount and the tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. All deferred tax assets and liabilities are classified as noncurrent in our consolidated balance sheet in accordance with ASU 2015-17, “ Income Taxes: Balance Sheet Classification of Deferred Taxes.” We record net deferred tax assets to the extent we believe these assets will more likely than not be realized. In making such determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies, recent financial operations and their associated valuation allowances, if any. In the event we were to determine that we would be able to realize or not realize our deferred income tax assets in the future in their net recorded amount, we would make an adjustment to the valuation allowance, which would reduce or increase the provision for income taxes, respectively. Certain provisions of ASC 740, “Income Taxes On December 22, 2017, the Tax Act was signed into law. The Tax Act contains significant changes to corporate taxation, including (i) the reduction of the corporate income tax rate to 21%, (ii) the acceleration of expensing for certain business assets, (iii) the one-time transition tax related to the transition of U.S. international tax from a worldwide tax system to a territorial tax system, (iv) the repeal of the domestic production deduction, (v) additional limitations on the deductibility of interest expense and (vi) expanded limitations on executive compensation. See “ Note 5. Income Taxes.
Pension and Other Postretirement Plans	Pension and Other Postretirement Benefits We account for pension and other postretirement benefits in accordance with ASC 715, “ Compensation – Retirement Benefits “ Note 4. Retirement Plans ”, The amount of unrecognized actuarial gains and losses recognized in the current year’s operations is based on amortizing the unrecognized gains or losses for each plan that exceed the larger of 10% of the projected benefit obligation or the fair value of plan assets, also known as “the corridor”. The amount of unrecognized gain or loss that exceeds the corridor is amortized over the average future service of the plan participants or the average life expectancy of inactive plan participants for plans where all or almost all of the plan participants are inactive. While we believe that our assumptions are appropriate, significant differences in our actual experience or significant changes in our assumptions may materially affect our pension and other postretirement benefit obligations and our future expense.
Share-based Compensation	Share-Based Compensation We recognize expense for share-based compensation plans based on the estimated fair value of the related awards in accordance with ASC 718, “ Compensation – Stock Compensation SAR SARs “ Note 20. Share-Based Compensation ”
Asset Retirement Obligation	Asset Retirement Obligations The Company accounts for asset retirement obligations in accordance with ASC 410, “ Asset Retirement and Environmental Obligations
Repair and Maintenance Costs	Repair and Maintenance Costs We expense routine repair and maintenance costs as we incur them. We defer certain expenses we incur during planned major maintenance activities and recognize the expenses ratably over the shorter of the estimated interval until the next major maintenance activity or the life of the deferred item. This maintenance is generally performed every twelve to twenty-four months and has a significant impact on our results of operations in the period performed primarily due to lost production during the maintenance period. Planned major maintenance costs deferred at September 30, 2018 and 2017 were $83.4 million and 80.8 million, respectively. The assets are recorded as other assets on the consolidated balance sheets.
Foreign Currency	Foreign Currency We translate the assets and liabilities of our foreign operations from their functional currency into U.S. dollars at the rate of exchange in effect as of the balance sheet date. We reflect the resulting translation adjustments in equity. We translate the revenues and expenses of our foreign operations at a daily average rate prevailing for each month during the fiscal year. We include gains or losses from foreign currency transactions, such as those resulting from the settlement of foreign receivables or payables, in the consolidated statements of operations. We recorded a gain on foreign currency transactions of $12.2 million and $4.3 million
Environmental Costs Remediation Costs	Environmental Remediation Costs We accrue for losses associated with our environmental remediation obligations when it is probable that we have incurred a liability and the amount of the loss can be reasonably estimated. We generally recognize accruals for estimated losses from our environmental remediation obligations no later than completion of the remedial feasibility study and adjust such accruals as further information develops or circumstances change. We recognize recoveries of our environmental remediation costs from other parties as assets when we deem their receipt probable. See “ Note 17. Commitments and Contingencies.
New Accounting Pronouncements - Recently Adopted	New Accounting Standards - Recently Adopted In May 2017, the FASB issued Compensation – Stock Compensation: Scope of Modification Accounting Compensation – Stock Compensation In March 2017, the FASB issued ASU 2017-07, “ Compensation: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The adoption resulted in a change in our operating profit, which was offset by a corresponding change in non-operating pension income (expense) to reflect the impact of presenting the non-service income (cost) component of net periodic pension income (expense) outside of operating income. In February 2017, the FASB issued ASU 2017-05, “ Other Income: Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets In January 2017, the FASB issued ASU 2017-01, “ Clarifying the Definition of a Business Business Combinations In November 2016, the FASB issued ASU 2016-18, “ Restricted Cash Statement of Cash Flows In October 2016, the FASB issued ASU 2016-16, “ Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory In August 2016, the FASB issued ASU 2016-15 “ Classification of Certain Cash Receipts and Cash Payments Statement of Cash Flows In May 2014, the FASB issued ASU 2014-09, which is codified in ASC 606 “ Revenue from Contracts with Customers Revenue Recognition We adopted the provisions of ASU 2014-09 on October 1, 2018. We manufacture certain products that have no alternative use to us (since such products are made to specific customer orders), and we believe that for certain customers we have a legally enforceable right to payment for performance completed to date on these manufactured products, including a reasonable profit. Beginning in fiscal year 2019, for manufactured products that meet these two criteria, the Company will recognize revenue “over time”. This results in (i) revenue recognition prior to the date of shipment or title transfer for these products, and (ii) increases the contract asset (unbilled receivables) balance with a corresponding reduction in finished goods inventory on our balance sheet. The Company elected the modified retrospective implementation approach and estimates accelerating revenue of approximately $175 million to $225 million. The transition adjustment related to this acceleration of revenue along with the related costs of goods sold and income tax effect will be recorded in the opening balance sheet within retained earnings. The Company has also identified and implemented changes to our accounting policies and practices, business processes, systems and designed and implemented specific controls over our evaluation of the impact of the new guidance on the Company upon adoption, and on an ongoing basis, including disclosure requirements and the collection of relevant data into the reporting process. While we are substantially complete with the process of quantifying the impacts that will result from applying the new standard, our assessment will be finalized during the first quarter of fiscal 2019.
New Accounting Pronouncements Recently Issued	New Accounting Standards - Recently Issued In August 2018, the FASB issued ASU 2018-15 “ Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. In August 2018, the FASB issued ASU 2018-14 “ Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Changes to the Disclosure Requirements for Defined Benefit Plans In August 2018, the FASB issued ASU 2018-13 “ Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement In June 2018, the FASB issued ASU 2018-07 “ Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Compensation – Stock Compensation In February 2018, the FASB issued ASU 2018-02, “ Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income Income Statement: Reporting Comprehensive Income In August 2017, the FASB issued ASU 2017-12, “ Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Test for Goodwill Impairment Intangibles – Goodwill and Other”. In June 2016, the FASB issued ASU 2016-13 “ Financial Instruments – Credit losses: Measurement of Credit Losses on Financial Instruments Financial Instruments-Credit Loss”. In February 2016, the FASB issued ASU 2016-02 “ Leases”, Leases” Leases

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2018
Description Of Business And Summary Of Significant Accounting Policies [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	The following table represents a summary of the changes in the reserve for allowance for doubtful accounts, returns and allowances and cash discounts for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 45.8 $ 36.5 $ 29.5 Reduction in sales and charges to costs and expenses 202.8 215.6 200.8 Deductions (198.9 ) (206.3 ) (193.8 ) Balance at end of fiscal year $ 49.7 $ 45.8 $ 36.5
Property, Plant and Equipment, Estimated Useful Lives	For financial reporting purposes, we provide depreciation and amortization primarily on a straight-line method generally over the estimated useful lives of the assets as follows: Buildings and building improvements 15-40 years Machinery and equipment 3-25 years Transportation equipment 3-8 years

Mergers, Acquisitions and Inv_2

Mergers, Acquisitions and Investment (Tables)	12 Months Ended
	Sep. 30, 2018
MPS [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The following table summarizes the weighted average life and the allocation to intangible assets recognized in the MPS Acquisition, excluding goodwill (in millions): Weighted Avg. Life Amounts Recognized as of the Acquisition Date Customer relationships 14.6 $ 1,008.7 Trademarks and tradenames 3.0 15.2 Photo library 10.0 2.5 Total 14.4 $ 1,026.4

Restructuring and Other Costs (

Restructuring and Other Costs (Tables)	12 Months Ended
	Sep. 30, 2018
Restructuring And Other Costs [Abstract]
Schedule of Restructuring and Other Costs	The following table summarizes our Restructuring and other costs for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Restructuring $ 39.5 $ 113.4 $ 294.9 Other 65.9 83.3 71.5 Restructuring and Other Costs $ 105.4 $ 196.7 $ 366.4
Schedule of Restructuring Charges Related to Active Restructuring Initiatives	The following table presents a summary of restructuring charges related to active restructuring initiatives that we incurred during the last three fiscal years, the cumulative recorded amount since we started the initiative, and our estimate of the total we expect to incur (in millions): 2018 2017 2016 Cumulative Total Expected Corrugated Packaging Net property, plant and equipment costs $ 2.8 $ 1.4 $ 184.5 $ 211.5 $ 211.5 Severance and other employee costs 1.6 3.3 17.4 42.2 42.8 Equipment and inventory relocation costs 3.1 1.9 0.3 7.1 7.1 Facility carrying costs 3.2 5.4 18.9 36.7 37.9 Other costs (0.1 ) (1.2 ) 9.1 19.1 19.1 Restructuring total $ 10.6 $ 10.8 $ 230.2 $ 316.6 $ 318.4 Consumer Packaging Net property, plant and equipment costs $ 6.9 $ 28.3 $ 3.8 $ 41.6 $ 41.6 Severance and other employee costs 7.2 26.4 4.6 41.0 41.2 Equipment and inventory relocation costs 2.7 2.8 1.1 7.4 7.9 Facility carrying costs 1.0 0.7 0.5 3.4 4.0 Other costs (1) 2.2 20.2 — 22.9 22.9 Restructuring total $ 20.0 $ 78.4 $ 10.0 $ 116.3 $ 117.6 Land and Development Net property, plant and equipment costs $ — $ 1.8 $ — $ 1.8 $ 1.8 Severance and other employee costs 0.3 2.8 10.6 13.7 13.7 Other costs 3.0 $ — $ — 3.0 3.0 Restructuring total $ 3.3 $ 4.6 $ 10.6 $ 18.5 $ 18.5 Corporate Net property, plant and equipment costs $ — $ 0.1 $ 1.2 $ 1.4 $ 1.4 Severance and other employee costs 0.8 14.8 36.9 100.6 100.6 Other costs 4.8 4.7 6.0 15.5 15.5 Restructuring total $ 5.6 $ 19.6 $ 44.1 $ 117.5 $ 117.5 Total Net property, plant and equipment costs $ 9.7 $ 31.6 $ 189.5 $ 256.3 $ 256.3 Severance and other employee costs 9.9 47.3 69.5 197.5 198.3 Equipment and inventory relocation costs 5.8 4.7 1.4 14.5 15.0 Facility carrying costs 4.2 6.1 19.4 40.1 41.9 Other costs 9.9 23.7 15.1 60.5 60.5 Restructuring total $ 39.5 $ 113.4 $ 294.9 $ 568.9 $ 572.0 (1) Includes a $17.6 million impairment of a customer relationship intangible in fiscal 2017 related to an exited product line.
Schedule of Acquisition, Divestiture and Integration Costs	The following table presents our acquisition, divestiture and integration costs that we incurred during the last three fiscal years (in millions): 2018 2017 2016 Acquisition costs $ 38.2 $ 27.1 $ 8.9 Integration costs 27.4 46.4 62.1 Divestiture costs 0.3 9.8 0.5 Other total $ 65.9 $ 83.3 $ 71.5
Schedule of Changes in Restructuring Accrual and Reconciliation of Accrual Charges	The following table summarizes the changes in the restructuring accrual, which are primarily composed of lease commitments, accrued severance and other employee costs, and a reconciliation of the restructuring accrual charges to the line item “ Restructuring and other costs ” on our consolidated statements of operations for the last three fiscal years (in millions): 2018 2017 2016 Accrual at beginning of fiscal year $ 47.4 $ 44.8 $ 21.4 Accruals acquired in acquisition — 3.5 — Additional accruals 16.5 63.2 75.3 Payments (29.8 ) (53.3 ) (51.9 ) Adjustment to accruals (1.0 ) (10.8 ) — Foreign currency rate changes (1.5 ) — — Accrual at end of fiscal year $ 31.6 $ 47.4 $ 44.8 Reconciliation of accruals and charges to restructuring and other costs (in millions): 2018 2017 2016 Additional accruals and adjustments to accruals (see table above) $ 15.5 $ 52.4 $ 75.3 Acquisition costs 38.2 27.1 8.9 Integration costs 22.0 41.2 59.8 Divestiture costs 0.3 9.8 0.5 Net property, plant and equipment 9.7 31.6 189.5 Severance and other employee costs 1.3 3.8 11.5 Equipment and inventory relocation costs 5.8 4.7 1.4 Facility carrying costs 4.2 6.1 19.5 Other costs 8.4 20.0 — Total restructuring and other costs, net $ 105.4 $ 196.7 $ 366.4

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Sep. 30, 2018
Retirement Plans [Abstract]
Schedule of Allocation of Plan Assets	Target Allocations U.S. Plans Non-U.S. Plans 2018 2017 2018 2017 Equity investments 15% 15% 22% 24% Fixed income investments 75% 70% 70% 65% Short-term investments 1% 1% 1% 1% Other investments 9% 14% 7% 10% Total 100% 100% 100% 100% Our asset allocations by asset category at September 30 were as follows: U.S. Plans Non-U.S. Plans 2018 2017 2018 2017 Equity investments 14% 13% 23% 26% Fixed income investments 73% 73% 69% 64% Short-term investments 3% 3% 2% 3% Other investments 10% 11% 6% 7% Total 100% 100% 100% 100%
Schedule of Weighted-Average Assumptions Used	The weighted average assumptions used to measure the benefit plan obligations at September 30, were: Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.50 % 3.42 % 4.09 % 3.26 % Rate of compensation increase 3.00 % 2.67 % 3.00 % 3.17 % Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Pension Plans 2018 2017 2016 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.09 % 3.26 % 4.30 % 3.08 % 4.70 % 3.89 % Rate of compensation increase 3.00 % 2.65 % 3.00 % 3.09 % 2.50 % 3.10 % Expected long-term rate of return on plan assets 6.50 % 4.98 % 6.50 % 6.03 % 5.88 % 6.34 % The weighted average assumptions used to measure the benefit plan obligations at September 30 were: Postretirement plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.50 % 6.61 % 4.09 % 6.51 % Rate of compensation increase N/A N/A N/A 7.37 % Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Postretirement Plans 2018 2017 2016 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 4.09 % 6.51 % 4.04 % 6.64 % 4.70 % 6.84 % Rate of compensation increase N/A 7.37 % N/A 3.14 % N/A 3.10 %
Schedule of Changes in Benefit Obligations	The following table shows the changes in benefit obligation and plan assets, and the plan’s funded status for the years ended September 30 (in millions): Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Change in projected benefit obligation: Benefit obligation at beginning of fiscal year $ 3,941.9 $ 1,502.2 $ 4,231.7 $ 925.2 Service cost 36.7 8.0 38.0 7.1 Interest cost 157.7 46.9 165.2 32.6 Amendments 9.3 — 3.5 — Actuarial gain (186.8 ) (90.3 ) (149.1 ) (57.6 ) Plan participant contributions — 2.5 — 1.7 Special termination benefits — — 12.5 — Benefits paid (175.3 ) (82.8 ) (141.4 ) (65.1 ) Business combinations — 3.5 — 621.0 Curtailments — (0.7 ) — — Settlements — (5.5 ) (229.3 ) (0.4 ) Foreign currency rate changes — (43.6 ) — 65.1 Other adjustments — — 10.8 — Business divestitures — — — (27.4 ) Benefit obligation at end of fiscal year $ 3,783.5 $ 1,340.2 $ 3,941.9 $ 1,502.2 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ 4,107.9 $ 1,414.7 $ 4,301.5 $ 774.1 Actual (loss) gain on plan assets (24.9 ) 39.9 104.2 2.4 Employer contributions 13.5 24.2 15.3 19.2 Plan participant contributions — 2.5 — 1.7 Benefits paid (175.3 ) (82.8 ) (141.4 ) (65.1 ) Business combinations — 0.7 — 622.1 Settlements — (5.5 ) (229.3 ) (0.4 ) Business divestitures — — — (0.7 ) Foreign currency rate changes — (43.5 ) — 61.4 Other adjustments — — 57.6 — Fair value of plan assets at end of fiscal year $ 3,921.2 $ 1,350.2 $ 4,107.9 $ 1,414.7 Funded status $ 137.7 $ 10.0 $ 166.0 $ (87.5 ) Amounts recognized in the consolidated balance sheet: Non-current assets $ 305.7 $ 114.3 $ 340.4 $ 27.6 Other current liability (10.1 ) (0.9 ) (9.3 ) (0.8 ) Accrued pension and other long-term benefits (157.9 ) (103.4 ) (165.1 ) (114.3 ) Over (under) funded status at end of fiscal year $ 137.7 $ 10.0 $ 166.0 $ (87.5 ) The following table shows the changes in benefit obligation and plan assets, and the plan’s funded status for the fiscal years ended September 30 (in millions): Postretirement Plans 2018 2017 Change in projected benefit obligation: U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Benefit obligation at beginning of fiscal year $ 98.1 $ 68.1 $ 90.7 $ 62.6 Service cost 0.7 0.8 0.1 0.8 Interest cost 3.9 4.0 3.3 4.1 Amendments (1.4 ) — (3.4 ) (1.0 ) Actuarial (gain) loss (2.5 ) (5.2 ) 14.1 0.4 Benefits paid (7.8 ) (2.6 ) (8.0 ) (2.7 ) Business combinations — — 1.3 2.0 Business divestitures — — — (0.4 ) Curtailments — (2.1 ) — (0.3 ) Foreign currency rate changes — (7.5 ) — 2.6 Benefit obligation at end of fiscal year $ 91.0 $ 55.5 $ 98.1 $ 68.1 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ — $ — $ — $ — Employer contributions 7.8 2.6 8.0 2.7 Plan participant contributions — — — — Benefits paid (7.8 ) (2.6 ) (8.0 ) (2.7 ) Fair value of plan assets at end of fiscal year $ — $ — $ — $ — Funded Status $ (91.0 ) $ (55.5 ) $ (98.1 ) $ (68.1 ) Amounts recognized in the consolidated balance sheet: Other current liability $ (8.8 ) $ (2.9 ) $ (9.8 ) $ (3.0 ) Accrued postretirement and other long-term benefits (82.2 ) (52.6 ) (88.3 ) (65.1 ) Under funded status at end of fiscal year $ (91.0 ) $ (55.5 ) $ (98.1 ) $ (68.1 )
Schedule of Accumulated and Projected Benefit Obligations	The pre-tax amounts in accumulated other comprehensive loss at September 30 not yet recognized as components of net periodic pension cost, including noncontrolling interest, consist of (in millions): Pension Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial loss $ 631.2 $ 105.6 $ 547.3 $ 173.9 Prior service cost 32.3 0.3 27.6 0.4 Total accumulated other comprehensive loss $ 663.5 $ 105.9 $ 574.9 $ 174.3 The pre-tax amounts in accumulated other comprehensive loss at September 30 not yet recognized as components of net periodic postretirement cost, including noncontrolling interest, consist of (in millions): Postretirement Plans 2018 2017 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial (gain) loss $ (11.2 ) $ (3.8 ) $ (9.1 ) $ 4.2 Prior service credit (11.3 ) (1.0 ) (13.9 ) (1.4 ) Total accumulated other comprehensive (income) loss $ (22.5 ) $ (4.8 ) $ (23.0 ) $ 2.8
Schedule of Amounts Recognized in Other Comprehensive (Income) Loss	The pre-tax amounts recognized in other comprehensive (income) loss, including noncontrolling interest, are as follows at September 30 (in millions): Pension Plans 2018 2017 2016 Net actuarial loss (gain) arising during period $ 38.7 $ (48.8 ) $ 355.4 Amortization and settlement recognition of net actuarial loss (20.6 ) (57.7 ) (381.6 ) Prior service cost arising during period 9.3 3.4 1.5 Amortization of prior service cost (4.7 ) (4.1 ) (3.9 ) Net other comprehensive loss (income) recognized $ 22.7 $ (107.2 ) $ (28.6 ) The pre-tax amounts recognized in other comprehensive (income) loss, including noncontrolling interest, are as follows at September 30 (in millions): Postretirement Plans 2018 2017 2016 Net actuarial (gain) loss arising during period $ (9.7 ) $ 14.7 $ (1.4 ) Amortization and settlement recognition of net actuarial (loss) gain (0.3 ) 1.3 1.9 Prior service credit arising during period (1.5 ) (4.4 ) (3.8 ) Amortization or curtailment recognition of prior service credit 4.4 4.5 2.1 Net other comprehensive (income) loss recognized $ (7.1 ) $ 16.1 $ (1.2 )
Schedule of Net Periodic Pension Cost	The net periodic pension cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Pension Plans 2018 2017 2016 Service cost $ 44.8 $ 45.1 $ 51.4 Interest cost 204.6 197.8 310.3 Expected return on plan assets (328.4 ) (313.1 ) (412.3 ) Amortization of net actuarial loss 21.2 25.4 11.0 Amortization of prior service cost 4.7 4.1 3.9 Curtailment gain (0.6 ) — (1.6 ) Settlement (gain) loss (0.5 ) 32.7 370.7 Special termination benefits — 12.5 18.4 Company defined benefit plan (income) expense (54.2 ) 4.5 351.8 Multiemployer and other plans 1.4 4.7 5.8 Net pension (income) cost $ (52.8 ) $ 9.2 $ 357.6 The net periodic postretirement cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Postretirement Plans 2018 2017 2016 Service cost $ 1.5 $ 0.9 $ 2.3 Interest cost 7.9 7.4 8.1 Amortization of net actuarial loss (gain) 0.3 (1.3 ) (2.0 ) Amortization of prior service credit (4.4 ) (4.5 ) (2.1 ) Curtailment gain (0.1 ) (0.3 ) — Net postretirement cost $ 5.2 $ 2.2 $ 6.3
Schedule of Estimated Losses (Gains) Amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost	The estimated losses that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2019 are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Actuarial loss $ 22.7 $ 5.3 Prior service cost 5.2 0.1 Total $ 27.9 $ 5.4 The estimated gains that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2019 are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Actuarial gain $ (1.1 ) $ (0.4 ) Prior service credit (2.6 ) (0.2 ) Total $ (3.7 ) $ (0.6 )
Schedule of Estimated Benefit Payments	Our projected estimated benefit payments (unaudited), which reflect expected future service, as appropriate, are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Fiscal 2019 $ 209.1 $ 80.1 Fiscal 2020 $ 218.6 $ 80.9 Fiscal 2021 $ 223.0 $ 79.8 Fiscal 2022 $ 231.7 $ 80.0 Fiscal 2023 $ 218.5 $ 80.2 Fiscal Years 2024 – 2028 $ 1,168.9 $ 398.9 Our projected estimated benefit payments (unaudited), which reflect expected future service, as appropriate, are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Fiscal 2019 $ 9.3 $ 2.9 Fiscal 2020 $ 8.2 $ 3.0 Fiscal 2021 $ 7.8 $ 3.1 Fiscal 2022 $ 7.4 $ 3.2 Fiscal 2023 $ 7.1 $ 3.3 Fiscal Years 2024 – 2028 $ 31.4 $ 19.1
Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis	The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2018 (in millions): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Equity securities: U.S. equities (1) $ 165.5 $ 165.5 $ — Non-U.S. equities (1) 8.2 8.2 — Fixed income securities: U.S. government securities (2) 435.8 — 435.8 Non-U.S. government securities (3) 127.5 — 127.5 U.S. corporate bonds (3) 1,493.6 108.4 1,385.2 Non-U.S. corporate bonds (3) 380.8 49.3 331.5 Other fixed income (4) 319.4 — 319.4 Short-term investments (5) 149.0 149.0 — Benefit plan assets measured in the fair value hierarchy $ 3,079.8 $ 480.4 $ 2,599.4 Assets measured at NAV (6) 2,191.6 Total benefit plan assets $ 5,271.4 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2017 (in millions): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Equity securities: U.S. equities (1) $ 136.7 $ 136.6 $ 0.1 Non-U.S. equities (1) 40.0 40.0 — Fixed income securities: U.S. government securities (2) 452.0 — 452.0 Non-U.S. government securities (3) 130.0 — 130.0 U.S. corporate bonds (3) 1,515.4 92.3 1,423.1 Non-U.S. corporate bonds (3) 373.7 51.1 322.6 Mortgage-backed securities (3) 0.1 — 0.1 Other fixed income (4) 311.4 — 311.4 Short-term investments (5) 184.6 184.6 — Benefit plan assets measured in the fair value hierarchy $ 3,143.9 $ 504.6 $ 2,639.3 Assets measured at NAV (6) 2,378.7 Total benefit plan assets $ 5,522.6 (1) Equity securities are comprised of the following investment types: (i) common stock, (ii) preferred stock and (iii) equity exchange traded funds. Level 1 investments in common and preferred stocks and exchange traded funds are valued using quoted market prices multiplied by the number of shares owned. (2) U.S. government securities include treasury and agency debt. These investments are valued using broker quotes in an active market. (3) The level 1 non-U.S. government securities investment is an exchange traded fund valued using quoted market prices. The level 1 U.S. corporate bonds category is primarily comprised of U.S. dollar denominated investment grade securities and valued using quoted market prices. Level 2 investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads, and/or other applicable reference data. (4) Other fixed income is comprised of municipal and asset-backed securities. Investments are valued utilizing a market approach that includes various valuation techniques and sources, such as broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads and/or other applicable reference data. (5) Short-term investments are valued at $1.00/unit, which approximates fair value. Amounts are generally invested in interest-bearing accounts. (6) NAV
Summary of Assets Measured at Fair Value Based on NAV Per Share	The following table summarizes assets measured at fair value based on NAV per share as a practical expedient as of September 30, 2018 and 2017 (in millions): Fair value Redemption Frequency Redemption Notice Period Unfunded Commitments September 30, 2018 Hedge funds (1) $ 47.9 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,092.9 Monthly Up to 60 days 75.3 Fixed income and fixed income related instruments (3) 1,050.8 Monthly Up to 10 days — $ 2,191.6 $ 75.3 September 30, 2017 Hedge funds (1) $ 64.2 Quarterly Up to 91 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,207.6 Monthly Up to 60 days 98.8 Fixed income and fixed income related instruments (3) 1,106.9 Monthly Up to 10 days — $ 2,378.7 $ 98.8 (1) Hedge fund investments are primarily made through shares of limited partnerships or similar structures. Hedge funds are typically valued monthly by third-party administrators that have been appointed by the funds’ general partners. Hedge funds have been valued using NAV as a practical expedient. (2) Commingled fund investments are valued at the net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled funds have been valued using NAV as a practical expedient. (3) Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled debt funds have been valued using NAV as a practical expedient. We maintain holdings in certain private equity partnerships and private real estate investments for which a liquid secondary market does not exist. The private equity partnerships are commingled investments. Valuation techniques, such as discounted cash flow and market based comparable analyses, are used to determine fair value of the private equity investments. Unobservable inputs used for the discounted cash flow technique include projected future cash flows and the discount rate used to calculate present value. Unobservable inputs used for the market-based comparisons technique include earnings before interest, taxes, depreciation and amortization multiples in other comparable third-party transactions, price to earnings ratios, liquidity, current operating results, as well as input from general partners and other pertinent information. Private equity investments have been valued using NAV as a practical expedient. Private real estate investments are commingled investments. Valuation techniques, such as discounted cash flow and market based comparable analyses, are used to determine fair value of the private equity investments. Unobservable inputs used for the discounted cash flow technique include projected future cash flows and the discount rate used to calculate present value. Unobservable inputs used for the market-based comparison technique include a combination of third party appraisals, replacement cost, and comparable market prices. Private real estate investments have been valued using NAV as a practical expedient. Equity-related investments are hedged equity investments in a commingled fund that consist primarily of equity indexed investments which are hedged by options and also hold collateral in the form of short term treasury securities. Equity related investments have been valued using NAV as a practical expedient.
Schedule of Health Care Cost Trend Rates	The assumed health care cost trend rates used in measuring the accumulated postretirement benefit obligation (“ APBO U.S. Plans Health care cost trend rate assumed for next year 6.03 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.43 % Year the rate reaches the ultimate trend rate 2037 Non-U.S. Plans Health care cost trend rate assumed for next year 5.51 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.51 % Year the rate reaches the ultimate trend rate 2018
Schedule of Multiemployer Plans	The following table lists our participation in our multiemployer and other plans that are individually significant for the years ended September 30 (in millions): Pension Fund EIN / Pension Plan Number Pension Act Zone Status FIP / RP Status Pending / Implemented Contributions (1) Surcharge imposed? Expiration CBA 2018 2017 2018 2017 2016 U.S. Multiemployer plans: Pace Industry Union- Management Pension Fund (2) 11-6166763 / 001 Red Red Implemented $ 0.9 $ 3.5 $ 3.3 Yes 9/30/20 to 6/25/23 Other Funds (3) 0.5 1.6 1.2 Total Contributions: $ 1.4 $ 5.1 $ 4.5 (1) (2) Our contributions for fiscal 2017 and 2016 exceeded 5% of total plan contributions. Although the plan data for fiscal 2018 is not yet available, we do not expect to continue to exceed 5% of total plan contributions due to our submission of notification to withdraw from PIUMPF. (3) Two additional MEPPs in which we participate have been certified as critical and declining.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2018
Tax Provision [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The components of income (loss) from continuing operations before income taxes are as follows (in millions): Year Ended September 30, 2018 2017 2016 United States $ 736.7 $ 481.9 $ (25.1 ) Foreign 298.1 375.7 269.7 Income from continuing operations before income taxes $ 1,034.8 $ 857.6 $ 244.6
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense (benefit) from continuing operations consists of the following components (in millions): Year Ended September 30, 2018 2017 2016 Current income taxes: Federal $ 83.0 $ 80.8 $ 98.3 State 26.8 3.3 12.8 Foreign 86.6 95.3 87.0 Total current expense 196.4 179.4 198.1 Deferred income taxes: Federal (1,108.6 ) 15.2 (131.5 ) State 53.2 (22.8 ) 6.9 Foreign (15.5 ) (12.8 ) 16.3 Total deferred (benefit) expense (1,070.9 ) (20.4 ) (108.3 ) Total income tax (benefit) expense $ (874.5 ) $ 159.0 $ 89.8
Schedule of Effective Income Tax Rate Reconciliation	The differences between the statutory federal income tax rate and our effective income tax rate from continuing operations are as follows: Year Ended September 30, 2018 2017 2016 Statutory federal tax rate 24.5 % 35.0 % 35.0 % Foreign rate differential 0.6 (4.9 ) (5.5 ) Adjustment and resolution of federal, state and foreign tax uncertainties 0.9 (0.3 ) 0.2 State taxes, net of federal benefit 4.3 3.3 4.9 Tax Act (1) (109.1 ) — — Excess tax benefit related to stock compensation (0.8 ) — — Research and development and other tax credits, net of valuation allowances and reserves (0.5 ) (0.8 ) (6.1 ) Income attributable to noncontrolling interest (0.1 ) 0.4 0.8 Domestic manufacturer’s deduction (1.8 ) (2.0 ) (4.4 ) Sale of HH&B — (5.0 ) — U.S. legal entity restructuring — (3.3 ) — Change in valuation allowance (1.8 ) (3.3 ) 6.3 Nondeductible transaction costs — 1.0 0.4 Contribution of assets to Grupo Gondi joint venture — — 3.4 Nontaxable increased cash surrender value (0.8 ) (1.5 ) (4.6 ) Withholding taxes 0.5 0.4 2.0 Brazilian net worth deduction (0.9 ) (0.8 ) (2.0 ) Other, net 0.5 0.3 6.3 Effective tax rate (84.5 )% 18.5 % 36.7 %
Schedule of Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to deferred income tax assets and liabilities consist of the following (in millions): September 30, 2018 2017 Deferred income tax assets: Accruals and allowances $ 22.1 $ 40.6 Employee related accruals and allowances 213.2 265.1 State net operating loss carryforwards 78.4 70.6 State credit carryforwards, net of federal benefit 64.8 54.4 U.S. and foreign tax credit carryforwards 14.7 135.9 Federal and foreign net operating loss carryforwards 188.7 204.1 Restricted stock and options 46.7 81.0 Other 45.3 32.8 Total 673.9 884.5 Deferred income tax liabilities: Property, plant and equipment 1,509.7 2,154.1 Deductible intangibles and goodwill 698.1 1,091.4 Inventory reserves 168.6 236.1 Deferred gain 258.8 405.2 Pension obligations 60.1 90.8 Basis difference in joint ventures 35.5 57.1 Other — 8.3 Total 2,730.8 4,043.0 Valuation allowances 229.4 219.1 Net deferred income tax liability $ 2,286.3 $ 3,377.6
Location of Deferred Taxes in Balance Sheet	Deferred taxes are recorded as follows in the consolidated balance sheet (in millions): September 30, 2018 2017 Long-term deferred tax asset (1) $ 35.2 $ 32.6 Long-term deferred tax liability 2,321.5 3,410.2 Net deferred income tax liability $ 2,286.3 $ 3,377.6 (1) The long-term deferred tax asset is presented in Other assets on the consolidated balance sheets.
Summary of Valuation Allowance	The following table represents a summary of the valuation allowances against deferred tax assets for fiscal 2018, 2017 and 2016 (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 219.1 $ 177.2 $ 100.2 Increases 50.8 54.3 24.8 Allowances related to purchase accounting (1) 0.1 12.4 63.0 Reductions (40.6 ) (24.8 ) (10.8 ) Balance at end of fiscal year $ 229.4 $ 219.1 $ 177.2 (1) Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition.
Summary of Income Tax Contingencies	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in millions): 2018 2017 2016 Balance at beginning of fiscal year $ 148.9 $ 166.8 $ 106.6 Additions related to purchase accounting (1) 3.4 7.7 16.5 Additions for tax positions taken in current year 3.1 5.0 30.3 Additions for tax positions taken in prior fiscal years 18.0 15.2 20.6 Reductions for tax positions taken in prior fiscal years (5.3 ) (25.6 ) (9.7 ) Reductions due to settlement (2) (29.4 ) (14.1 ) (1.3 ) (Reductions) additions for currency translation adjustments (9.6 ) 2.0 7.0 Reductions as a result of a lapse of the applicable statute of limitations (2.0 ) (8.1 ) (3.2 ) Balance at end of fiscal year $ 127.1 $ 148.9 $ 166.8 (1) Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition. (2) Amounts in fiscal 2018 relate to the settlement of state audit examinations and federal and state amended returns filed related to affirmative adjustments for which a there was a reserve. Amounts in fiscal 2017 relate to the settlement of federal and state audit examinations with taxing authorities.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Revenue from External Customers, Segment Income and Long-Lived Assets, by Geographical Areas	. The table below reflects financial data of our foreign operations for each of the past three fiscal years, some of which were transacted in U.S. dollars (in millions, except percentages): Years Ended September 30, 2018 2017 2016 Foreign net sales to unaffiliated customers $ 3,236.7 $ 2,621.2 $ 2,426.6 Foreign segment income $ 360.7 $ 260.1 $ 226.1 Foreign long-lived assets $ 1,400.2 $ 1,558.3 $ 1,341.5 Foreign operations as a percent of consolidated operations: Foreign net sales to unaffiliated customers 19.9 % 17.6 % 17.1 % Foreign segment income 21.4 % 21.8 % 18.4 % Foreign long-lived assets 15.4 % 17.1 % 14.4 %
Certain Operating Data for Segments	The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2018 2017 2016 Net sales (aggregate): Corrugated Packaging $ 9,103.4 $ 8,408.3 $ 7,868.5 Consumer Packaging 7,291.4 6,452.5 6,388.1 Land and Development 142.4 243.8 119.8 Total $ 16,537.2 $ 15,104.6 $ 14,376.4 Less net sales (intersegment): Corrugated Packaging $ 161.6 $ 155.8 $ 136.2 Consumer Packaging 90.5 89.1 68.4 Total $ 252.1 $ 244.9 $ 204.6 Net sales (unaffiliated customers): Corrugated Packaging $ 8,941.8 $ 8,252.5 $ 7,732.3 Consumer Packaging 7,200.9 6,363.4 6,319.7 Land and Development 142.4 243.8 119.8 Total $ 16,285.1 $ 14,859.7 $ 14,171.8 Segment income: Corrugated Packaging $ 1,207.9 $ 753.9 $ 739.9 Consumer Packaging 454.6 425.8 481.7 Land and Development 22.5 13.8 4.6 Segment income 1,685.0 1,193.5 1,226.2 Multiemployer pension withdrawals (184.2 ) — — Pension risk transfer expense — — (370.7 ) Pension lump sum settlement — (32.6 ) — Land and Development impairments (31.9 ) (46.7 ) — Restructuring and other costs (105.4 ) (196.7 ) (366.4 ) Non-allocated expenses (47.5 ) (43.5 ) (49.1 ) Interest expense, net (293.8 ) (222.5 ) (212.5 ) Gain on extinguishment of debt (0.1 ) 1.8 2.7 Other income, net 12.7 11.5 14.4 Gain on sale of HH&B — 192.8 — Income from continuing operations before income taxes $ 1,034.8 $ 857.6 $ 244.6 The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2018 2017 2016 Identifiable assets: Corrugated Packaging $ 10,678.5 $ 10,537.7 $ 10,046.0 Consumer Packaging 11,902.2 11,877.8 10,122.5 Land and Development 49.1 89.8 460.6 Assets held for sale 59.5 173.6 52.3 Corporate 2,671.2 2,410.1 2,356.8 Total $ 25,360.5 $ 25,089.0 $ 23,038.2 Goodwill: Corrugated Packaging $ 1,890.9 $ 1,865.7 $ 1,722.5 Consumer Packaging 3,686.7 3,662.6 3,055.6 Total $ 5,577.6 $ 5,528.3 $ 4,778.1 Depreciation and amortization: Corrugated Packaging $ 676.8 $ 597.9 $ 576.2 Consumer Packaging 569.3 508.2 498.9 Land and Development 0.7 0.7 1.4 Discontinued operations — — 57.2 Corporate 5.4 5.3 8.2 Total $ 1,252.2 $ 1,112.1 $ 1,141.9 Capital expenditures: Corrugated Packaging $ 647.8 $ 492.1 $ 490.1 Consumer Packaging 317.8 265.8 244.9 Discontinued operations — — 45.2 Corporate 34.3 20.7 16.5 Total $ 999.9 $ 778.6 $ 796.7 Investment in unconsolidated entities: Corrugated Packaging $ 435.7 $ 321.1 $ 281.2 Consumer Packaging 21.7 24.7 22.2 Land and Development — 14.4 28.6 Corporate 0.4 0.4 (3.1 ) Total $ 457.8 $ 360.6 $ 328.9
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the fiscal years ended September 30, 2018, 2017 and 2016 are as follows (in millions): Corrugated Packaging Consumer Packaging Total Balance as of October 1, 2015 Goodwill $ 1,667.5 $ 3,022.4 $ 4,689.9 Accumulated impairment losses — (42.8 ) (42.8 ) 1,667.5 2,979.6 4,647.1 Goodwill acquired 52.4 8.0 60.4 Goodwill disposed of (24.0 ) — (24.0 ) Purchase price allocation adjustments (4.9 ) 67.6 62.7 Translation adjustments 31.5 0.4 31.9 Balance as of September 30, 2016 Goodwill 1,722.5 3,098.4 4,820.9 Accumulated impairment losses — (42.8 ) (42.8 ) 1,722.5 3,055.6 4,778.1 Goodwill acquired 137.6 907.8 1,045.4 Goodwill disposed of — (329.6 ) (329.6 ) Purchase price allocation adjustments (1.2 ) 9.3 8.1 Translation adjustments 6.8 19.5 26.3 Balance as of September 30, 2017 Goodwill 1,865.7 3,705.4 5,571.1 Accumulated impairment losses — (42.8 ) (42.8 ) 1,865.7 3,662.6 5,528.3 Goodwill acquired 65.4 23.8 89.2 Goodwill disposed of (4.2 ) — (4.2 ) Purchase price allocation adjustments 2.3 18.4 20.7 Translation adjustments (38.3 ) (18.1 ) (56.4 ) Balance as of September 30, 2018 Goodwill 1,890.9 3,729.5 5,620.4 Accumulated impairment losses — (42.8 ) (42.8 ) $ 1,890.9 $ 3,686.7 $ 5,577.6

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Sep. 30, 2018
Discontinued Operations And Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	The following table presents the financial results of Specialty Chemicals’ discontinued operations (in millions): 2016 Net sales $ 533.7 Cost of goods sold 387.5 Selling, general and administrative, excluding intangible amortization 65.6 Selling, general and administrative intangible amortization 28.8 Restructuring and other costs 49.5 Impairment of Specialty Chemicals goodwill and intangibles 579.4 Operating loss (577.1 ) Interest income (expense) and other income (expense), net 0.1 Loss from discontinued operations before income taxes (577.0 ) Income tax benefit 32.3 Loss from discontinued operations $ (544.7 ) The following table presents the significant non-cash items and capital expenditures for Specialty Chemicals’ that are included in the consolidated statements of cash flows (in millions): 2016 Depreciation, depletion and amortization $ 57.2 Impairment of Specialty Chemicals goodwill and intangibles $ 579.4 Capital expenditures $ (45.2 )

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories are as follows (in millions): September 30, 2018 2017 Finished goods and work in process $ 867.0 $ 905.0 Raw materials 730.0 614.2 Supplies and spare parts 368.2 360.7 Inventories at FIFO cost 1,965.2 1,879.9 LIFO reserve (135.6 ) (82.6 ) Net inventories $ 1,829.6 $ 1,797.3

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment consists of the following (in millions): September 30, 2018 2017 Property, plant and equipment at cost: Land and buildings $ 2,078.9 $ 2,034.3 Machinery and equipment 12,064.0 11,349.7 Forestlands and mineral rights 158.0 208.3 Transportation equipment 30.1 30.7 Leasehold improvements 88.9 59.5 14,419.9 13,682.5 Less: accumulated depreciation, depletion and amortization (5,337.4 ) (4,564.2 ) Property, plant and equipment, net $ 9,082.5 $ 9,118.3

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2018
Other Intangible Assets [Abstract]
Schedule of Finite-Lived Intangible Assets	The gross carrying amount and accumulated amortization relating to intangible assets, excluding goodwill, is as follows (in millions, except weighted avg. life): September 30, 2018 2017 Weighted Avg. Life (in years) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships 16.7 $ 4,123.7 $ (1,079.8 ) $ 4,046.2 $ (806.0 ) Favorable contracts 10.1 47.8 (34.8 ) 48.2 (30.7 ) Technology and patents 10.7 41.2 (18.0 ) 31.8 (14.4 ) Trademarks and tradenames 19.8 77.6 (43.9 ) 74.7 (31.4 ) Non-compete agreements 2.0 3.4 (1.7 ) 2.5 (0.6 ) License costs 9.6 24.6 (18.1 ) 23.6 (14.6 ) Total 16.6 $ 4,318.3 $ (1,196.3 ) $ 4,227.0 $ (897.7 )
Estimated intangible asset future amortization expense	Estimated intangible asset amortization expense for the succeeding five fiscal years is as follows (in millions): Fiscal 2019 $ 300.1 Fiscal 2020 $ 289.6 Fiscal 2021 $ 243.8 Fiscal 2022 $ 234.6 Fiscal 2023 $ 226.4

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Summary of Activity Under A/R Sales Agreement	The following table represents a summary of the activity under the A/R Sales Agreement and the New A/R Sales Agreement for fiscal 2018 and 2017 (in millions): 2018 2017 Receivable from financial institution at beginning of fiscal year $ 24.9 $ 13.8 Receivables sold to the financial institution and derecognized 1,664.0 1,542.5 Receivables collected by financial institution (1,573.8 ) (1,466.7 ) Cash proceeds from financial institution (115.1 ) (64.7 ) Receivable from financial institution at September 30, $ — $ 24.9

Debt (Tables)

Debt (Tables)	12 Months Ended
	Sep. 30, 2018
Debt [Abstract]
Schedule of Carrying Value and Weighted Average Interest Rate of Individual Components of Debt	The following were individual components of debt (in millions, except percentages): September 30, 2018 September 30, 2017 Carrying Value Weighted Avg Interest Rate Carrying Value Weighted Avg Interest Rate Public bonds due fiscal 2019 to 2022 $ 1,470.9 4.2 % $ 1,484.5 4.2 % Public bonds due fiscal 2023 to 2028 2,534.4 3.8 % 1,368.8 3.6 % Public bonds due fiscal 2030 to 2033 964.1 5.2 % 975.5 5.2 % Public bonds due fiscal 2037 to 2047 178.5 6.3 % 178.8 6.3 % Term loan facilities 599.4 3.7 % 1,622.7 2.5 % Revolving credit and swing facilities 355.0 3.2 % 436.4 1.1 % Receivables-backed financing facility — N/A 110.0 2.1 % Capital lease obligations 171.0 4.1 % 177.0 4.3 % Supplier financing and commercial card programs 105.1 N/A 130.3 N/A International and other debt 36.8 6.1 % 70.8 6.8 % Total debt 6,415.2 4.1 % 6,554.8 3.6 % Less: current portion of debt 740.7 608.7 Long-term debt due after one year $ 5,674.5 $ 5,946.1
Schedule of aggregate maturities of debt	As of September 30, 2018, the aggregate maturities of debt, excluding capital lease obligations, for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 726.6 Fiscal 2020 474.5 Fiscal 2021 350.3 Fiscal 2022 1,000.9 Fiscal 2023 350.1 Thereafter 3,136.6 Fair value of debt step-up, deferred financing costs and unamortized bond discounts 205.2 Total $ 6,244.2 As of September 30, 2018, the aggregate maturities of capital lease obligations for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 5.0 Fiscal 2020 4.2 Fiscal 2021 2.5 Fiscal 2022 2.1 Fiscal 2023 0.6 Thereafter 138.1 Fair value step-up 18.5 Total $ 171.0

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases	As of September 30, 2018, future minimum lease payments under all noncancelable operating leases for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2019 $ 132.1 Fiscal 2020 112.0 Fiscal 2021 87.9 Fiscal 2022 66.8 Fiscal 2023 51.6 Thereafter 165.4 Total future minimum lease payments $ 615.8

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Sep. 30, 2018
Other Comprehensive Income Loss [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Loss, Net of Tax	The following table summarizes the changes in accumulated other comprehensive loss by component for the fiscal years ended September 30, 2018 and 2017 (in millions): Deferred Loss on Cash Flow Hedges Defined Benefit Pension and Postretirement Plans Foreign Currency Items Available for Sale Security Total (1) Balance at September 30, 2016 $ (0.2 ) $ (523.8 ) $ (102.4 ) $ — $ (626.4 ) Other comprehensive income before reclassifications — 22.8 80.8 0.7 104.3 Amounts reclassified from accumulated other comprehensive (income) loss (0.5 ) 35.6 — — 35.1 Sale of HH&B — 2.9 26.8 — 29.7 Net current period other comprehensive loss (income) (0.5 ) 61.3 107.6 0.7 169.1 Balance at September 30, 2017 $ (0.7 ) $ (462.5 ) $ 5.2 $ 0.7 $ (457.3 ) Other comprehensive (loss) income before reclassifications — (18.6 ) (234.4 ) 0.8 (252.2 ) Amounts reclassified from accumulated other comprehensive loss (income) 0.5 15.2 — (1.5 ) 14.2 Net current period other comprehensive income (loss) 0.5 (3.4 ) (234.4 ) (0.7 ) (238.0 ) Balance at September 30, 2018 $ (0.2 ) $ (465.9 ) $ (229.2 ) $ — $ (695.3 ) (1) All amounts are net of tax and noncontrolling interest.
Summary of Reclassification out of Accumulated Other Comprehensive Loss	The following table summarizes the reclassifications out of accumulated other comprehensive loss by component for the fiscal years ended September 30, 2018 and 2017 (in millions): Years Ended September 30, 2018 2017 Pre-Tax Tax Net of Tax Pre-Tax Tax Net of Tax Amortization of defined benefit pension and postretirement items: (1) Actuarial gains (losses) (2) $ 20.9 (5.9 ) $ 15.0 $ (56.3 ) $ 20.4 $ (35.9 ) Prior service credits (2) 0.3 (0.1 ) 0.2 0.5 (0.2 ) 0.3 Sale of HH&B (3) — — — (4.2 ) 1.3 (2.9 ) Subtotal defined benefit plans 21.2 (6.0 ) 15.2 (60.0 ) 21.5 (38.5 ) Foreign currency translation adjustments: (1) Sale of HH&B (3) — — — (26.8 ) — (26.8 ) Available for sale security (4) (1.5 ) — (1.5 ) — — — Derivative Instruments: (1) Foreign currency cash flow hedges (4) 0.7 (0.2 ) 0.5 0.8 (0.3 ) 0.5 Total reclassifications for the period $ 20.4 $ (6.2 ) $ 14.2 $ (86.0 ) $ 21.2 $ (64.8 ) (1) Amounts in parentheses indicate charges to earnings. Amounts pertaining to noncontrolling interests are excluded. (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See “ Note 4. Retirement Plans (3) Included in gain on sale of HH&B. (4) These accumulated other comprehensive income components are included in net sales.
Schedule of Other Comprehensive (Loss) Income	A summary of the components of other comprehensive (loss) income, including noncontrolling interest, for the years ended September 30, 2018, 2017 and 2016, is as follows (in millions): Fiscal 2018 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (234.4 ) $ — $ (234.4 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 0.7 (0.2 ) 0.5 Net actuarial loss arising during period (29.0 ) 15.9 (13.1 ) Amortization and settlement recognition of net actuarial loss 20.9 (5.9 ) 15.0 Prior service cost arising during the period (7.8 ) 2.3 (5.5 ) Amortization of prior service cost 0.3 (0.1 ) 0.2 Unrealized gain on available for sale security 0.8 — 0.8 Reclassification adjustment of net gain on available for sale security included in earnings (1.5 ) — (1.5 ) Consolidated other comprehensive loss (250.0 ) 12.0 (238.0 ) Less: Other comprehensive income attributable to noncontrolling interests — — — Other comprehensive loss attributable to common stockholders $ (250.0 ) $ 12.0 $ (238.0 ) Fiscal 2017 Pre-Tax Tax Net of Tax Foreign currency translation gain $ 80.7 $ — $ 80.7 Sale of HH&B, foreign currency 26.8 — 26.8 Reclassification adjustment of net gain on cash flow hedges included in earnings (0.8 ) 0.3 (0.5 ) Net actuarial gain arising during period 34.1 (11.9 ) 22.2 Amortization and settlement recognition of net actuarial loss 56.4 (20.4 ) 36.0 Prior service credit arising during the period 1.0 (0.3 ) 0.7 Amortization of prior service credit (0.4 ) 0.2 (0.2 ) Unrealized gain on available for sale security 0.7 — 0.7 Sale of HH&B, defined benefit pension plans 4.2 (1.3 ) 2.9 Consolidated other comprehensive income 202.7 (33.4 ) 169.3 Less: Other comprehensive income attributable to noncontrolling interests (0.2 ) — (0.2 ) Other comprehensive income attributable to common stockholders $ 202.5 $ (33.4 ) $ 169.1 Fiscal 2016 Pre-Tax Tax Net of Tax Foreign currency translation gain $ 109.8 $ — $ 109.8 Deferred loss on cash flow hedges (0.7 ) 0.3 (0.4 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 1.9 (0.7 ) 1.2 Net actuarial loss arising during period (354.0 ) 129.4 (224.6 ) Amortization and settlement recognition of net actuarial loss (1) 379.7 (143.2 ) 236.5 Prior service credit arising during the period 2.3 (0.9 ) 1.4 Amortization of prior service cost 1.8 (0.7 ) 1.1 Sale of foreign subsidiary 20.2 — 20.2 Consolidated other comprehensive income 161.0 (15.8 ) 145.2 Less: Other comprehensive loss attributable to noncontrolling interests 0.7 — 0.7 Other comprehensive income attributable to common stockholders $ 161.7 $ (15.8 ) $ 145.9 (1) Includes pension risk transfer expense.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2018
Stock Based Compensation [Abstract]
Summary of Share-based Compensation Plans	The table below shows the approximate number of shares: available for issuance, available for future grant, to be issued if restricted awards granted with a performance condition recorded at target achieve the maximum award, and if new grants pursuant to the plan are expected to be issued, each as adjusted as necessary for corporate actions (in millions). Shares Available For Issuance Shares Available For Future Grant Shares To Be Issued If Performance Is Achieved At Maximum Expect To Make New Awards Amended and Restated 2016 Incentive Stock Plan (1) 11.7 8.0 2.5 Yes 2004 Incentive Stock Plan (1)(2) 15.8 3.1 0.0 No 2005 Performance Incentive Plan (1)(2) 12.8 9.0 0.0 No RockTenn (SSCC) Equity Inventive Plan (1)(3) 7.9 5.9 0.0 No (1) As part of the Separation, equity-based incentive awards were generally adjusted to maintain the intrinsic value of awards immediately prior to the Separation. The number of unvested restricted stock awards and unexercised stock options and SARs at the time of the Separation were increased by an exchange factor of approximately 1.12. In addition, the exercise price of unexercised stock options and SARs at the time of the Separation was converted to decrease the exercise price by an exchange factor of approximately 1.12. (2) In connection with the Combination, WestRock assumed all RockTenn and MWV equity incentive plans. We issued awards to certain key employees and our directors pursuant to our RockTenn 2004 Incentive Stock Plan, as amended, and our MWV 2005 Performance Incentive Plan, as amended. The awards were converted into WestRock awards using the conversion factor as described in Business Combination Agreement. (3) In connection with the Smurfit-Stone Acquisition, we assumed the Smurfit-Stone equity incentive plan, which was renamed the Rock-Tenn Company (SSCC) Equity Incentive Plan. The awards were converted into shares of RockTenn Common Stock, options and restricted stock units, as applicable, using the conversion factor as described in the merger agreement.
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	We applied the following weighted average assumptions to estimate the fair value of stock option grants made in the following period: 2016 Expected term in years 7.0 Expected volatility 38.3 % Risk-free interest rate 1.6 % Dividend yield 4.5 %
Summary of Changes in Stock Options	The table below summarizes the changes in all stock options during the fiscal year ended September 30, 2018: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2017 5,866,127 $ 30.51 Exercised (1,582,313 ) 21.73 Expired (5,819 ) 37.17 Forfeited (24,341 ) 32.13 Outstanding at September 30, 2018 4,253,654 $ 33.75 4.3 $ 85.8 Exercisable at September 30, 2018 3,845,523 $ 34.17 4.0 $ 76.1 Vested and expected to vest at September 30, 2018 4,251,748 $ 33.75 4.3 $ 85.7
Summary of Changes in SARs	The table below summarizes the changes in all SARs during the fiscal year ended September 30, 2018: SARs Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2017 51,016 $ 25.30 Exercised (9,935 ) 16.66 Expired (4,095 ) 27.69 Outstanding at September 30, 2018 36,986 $ 27.36 2.4 $ 1.0 Exercisable at September 30, 2018 36,986 $ 27.36 2.4 $ 1.0
Summary of restricted stock awards - vested, granted and changes	The table below summarizes the changes in unvested restricted stock during the fiscal year ended September 30, 2018: Shares/Units Weighted Average Grant Date Fair Value Unvested at September 30, 2017 (1) 2,959,449 $ 45.28 Granted 1,116,111 69.36 Vested (697,717 ) 57.39 Forfeited (153,669 ) 45.07 Unvested at September 30, 2018 (1) 3,224,174 $ 51.01 (1) Target awards granted with a performance condition, net of subsequent forfeitures, may be increased up to 200% of the target or decreased to zero, subject to the level of performance attained. The awards are reflected in the table at the target award amount of 100%. Based on current facts and assumptions we are forecasting the performance of the grants to be attained at levels that would result in the issuance of approximately 0.9 million additional shares. However, it is possible that the performance attained may vary. The following table represents a summary of restricted stock shares granted in fiscal 2018, 2017 and 2016 with terms defined in the applicable grant letters. The shares are not deemed to be issued and carry voting rights until the relevant conditions defined in the award documents have been met, unless otherwise noted. 2018 2017 2016 Shares of restricted stock granted to non-employee directors (1) 23,285 26,521 64,155 Shares of restricted stock granted to employees: Shares granted for attainment of a performance condition at an amount in excess of target (2) 45,964 340,319 447,261 Shares granted with a service condition and a Cash Flow Per Share performance condition at target (3) (4) 432,655 507,070 1,211,760 Shares granted with a service condition and a relative Total Shareholder Return market condition at target (3) 259,695 301,980 — Shares granted with a service condition (5) 354,512 309,850 27,370 Share of restricted stock assumed in purchase accounting: Shares granted with a service condition (6) — 119,373 — Total restricted stock granted 1,116,111 1,605,113 1,750,546 (1) Non-employee director grants generally vest over a period of up to one year and are deemed issued on the grant date and have voting and dividend rights. (2) (3) These employee grants vest over approximately three years and have adjustable ranges from 0 - 200% of target subject to the level of performance attained in the respective award agreement. The employee grants with a relative Total Shareholder Return condition were valued using a Monte Carlo simulation, the terms of which are outlined below. (4) Shares granted in fiscal 2015 were reduced by 50,326 shares at target related to the rescission of shares granted to our CEO that were inadvertently granted in excess of plan limits. (5) These shares vest over approximately three to four years. (6) These shares vest over approximately one to three years. The following table represents a summary of restricted stock vested in fiscal 2018, 2017 and 2016 (in millions, except shares): 2018 2017 2016 Shares of restricted stock vested 697,717 1,112,909 1,589,761 Aggregate fair value of restricted stock vested $ 46.1 $ 59.5 $ 57.5

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	September 30, 2018 2017 2016 Numerator: Income from continuing operations $ 1,909.3 $ 698.6 $ 154.8 Less: Net (income) loss from continuing operations attributable to noncontrolling interest (3.2 ) 9.6 (2.1 ) Income available to common stockholders, before discontinued operations 1,906.1 708.2 152.7 Less: Distributed and undistributed income available to participating securities (0.2 ) (0.1 ) — Distributed and undistributed income attributable to common stockholders, before discontinued operations 1,905.9 708.1 152.7 Loss from discontinued operations (1) — — (549.0 ) Net income (loss) attributable to common stockholders $ 1,905.9 $ 708.1 $ (396.3 ) Denominator: Basic weighted average shares outstanding 255.5 252.2 254.0 Effect of dilutive stock options and non-participating securities 4.3 3.5 3.9 Diluted weighted average shares outstanding 259.8 255.7 257.9 Basic earnings per share from continuing operations $ 7.46 $ 2.81 $ 0.60 Basic loss per share from discontinued operations — — (2.16 ) Basic earnings (loss) per share attributable to common stockholders $ 7.46 $ 2.81 $ (1.56 ) Diluted earnings per share from continuing operations $ 7.34 $ 2.77 $ 0.59 Diluted loss per share from discontinued operations — — (2.13 ) Diluted earnings (loss) per share attributable to common stockholders $ 7.34 $ 2.77 $ (1.54 ) (1) Net of income attributable to noncontrolling interests of discontinued operations of $4.3 million for the fiscal year ended September 30, 2016.

Financial Results by Quarter _2

Financial Results by Quarter (Unaudited) (Tables)	12 Months Ended
	Sep. 30, 2018
Financial Results By Quarter Unaudited [Abstract]
Schedule of Quarterly Financial Information	Fiscal 2018 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 3,894.0 $ 4,017.0 $ 4,137.5 $ 4,236.6 Cost of goods sold $ 3,111.6 $ 3,220.4 $ 3,264.3 $ 3,294.9 Multiemployer pension withdrawals $ 180.0 $ — $ 4.2 $ — Land and Development impairments $ 27.6 $ — $ 1.7 $ 2.6 Restructuring and other costs $ 16.3 $ 31.7 $ 17.1 $ 40.3 (Loss) gain on extinguishment of debt $ (1.0 ) $ 0.1 $ 0.9 $ (0.1 ) Income tax benefit (expense) $ 1,073.2 $ (18.8 ) $ (84.5 ) $ (95.4 ) Consolidated net income $ 1,133.5 $ 224.5 $ 271.3 $ 280.0 Net income attributable to common stockholders $ 1,135.1 $ 223.2 $ 268.2 $ 279.6 Basic earnings per share attributable to common stockholders $ 4.45 $ 0.87 $ 1.05 $ 1.10 Diluted earnings per share attributable to common stockholders $ 4.38 $ 0.86 $ 1.03 $ 1.08 Fiscal 2017 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 3,447.2 $ 3,656.3 $ 3,695.6 $ 4,060.6 Cost of goods sold $ 2,855.9 $ 2,980.9 $ 3,000.1 $ 3,282.6 Pension lump sum settlement $ — $ 28.7 $ — $ 3.9 Land and Development impairments $ — $ 42.7 $ — $ 4.0 Restructuring and other costs $ 81.0 $ 18.3 $ 59.4 $ 38.0 (Loss) gain on extinguishment of debt $ — $ (0.1 ) $ 2.0 $ (0.1 ) Gain on sale of HH&B $ — $ — $ 190.6 $ 2.2 Consolidated net income $ 78.5 $ 98.2 $ 326.6 $ 195.3 Net income attributable to common stockholders $ 80.9 $ 103.1 $ 328.1 $ 196.1 Basic earnings per share attributable to common stockholders $ 0.32 $ 0.41 $ 1.30 $ 0.77 Diluted earnings per share attributable to common stockholders $ 0.32 $ 0.40 $ 1.29 $ 0.76

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Dec. 22, 2017	Jan. 23, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Oct. 01, 2018
Description of Business and Summary of Significant Accounting Policies [Line Items]
Proceeds from sale of HH&B						$ 1,005,900,000
Gain on sale of HH&B			$ 2,200,000	$ 190,600,000		$ 192,800,000
Percentage of FIFO Inventory			32.00%		31.00%	32.00%
Interest Costs, Capitalized During Period					$ 8,200,000	$ 7,000,000	$ 7,600,000
Percentage of our mill assets as measured at cost with a life of 25 years or less					90.00%
Finite-Lived Intangible Assets, Useful Life					16 years 7 months 6 days
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period					3 years
Asset Retirement Obligation			$ 70,500,000		$ 72,900,000	70,500,000
Deferred maintenance costs			80,800,000		83,400,000	80,800,000
Foreign Currency Transaction Gain, after Tax					$ 12,200,000	4,300,000	$ (6,500,000)
Home, Health and Beauty Business [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Proceeds from sale of HH&B		$ 1,025,000,000
Foreign Pension Liabilities Divested Due to Sale of Business		$ 25,000,000
Gain on sale of HH&B						192,800,000
Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Approximate Range Receivables Due, Days					30 days
Finite-Lived Intangible Assets, Useful Life					1 year
Minimum [Member] | ASU 2014-09 [Member] | Subsequent Event [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Estimated transition adjustment of accelerated revenue to be recorded to opening balance of retained earnings								$ 175,000,000
Minimum [Member] | Building and Building Improvements [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					15 years
Minimum [Member] | Machinery and Equipment [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					3 years
Minimum [Member] | Transportation Equipment [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					3 years
Minimum [Member] | Leasehold Improvements [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					3 years
Maximum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Approximate Range Receivables Due, Days					60 days
Finite-Lived Intangible Assets, Useful Life					40 years
Maximum [Member] | ASU 2014-09 [Member] | Subsequent Event [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Estimated transition adjustment of accelerated revenue to be recorded to opening balance of retained earnings								$ 225,000,000
Maximum [Member] | Building and Building Improvements [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					40 years
Maximum [Member] | Machinery and Equipment [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					25 years
Maximum [Member] | Transportation Equipment [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					8 years
Maximum [Member] | Machinery and Equipment, Mills [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					44 years
Maximum [Member] | Cost of Our Mill Machinery and Equipment with a Life of 25 Years or Less
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					25 years
Maximum [Member] | Leasehold Improvements [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life					10 years
Restricted Stock, Non-Employee Directors [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period					1 year
Foreign Exchange Contract [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Derivative, Notional Amount			47,800,000		$ 356,000,000	47,800,000
Interest Rate Contract [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Derivative, Notional Amount			0		0	0
Commodity Contract [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Derivative, Notional Amount			$ 0		$ 0	$ 0

Description of Business and S_5

Description of Business and Summary of Significant Accounting Policies - Schedule of Valuation and Qualifying Accounts Disclosure (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of fiscal year	$ 45.8	$ 36.5	$ 29.5
Reduction in sales and charges to costs and expenses	202.8	215.6	200.8
Deductions	(198.9)	(206.3)	(193.8)
Balance at end of fiscal year	$ 49.7	$ 45.8	$ 36.5

Description of Business and S_6

Description of Business and Summary of Significant Accounting Policies - Property, Plant and Equipment, Estimated Useful Lives (Details)	12 Months Ended
	Sep. 30, 2018
Building and Building Improvements [Member] | Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Building and Building Improvements [Member] | Maximum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Machinery and Equipment [Member] | Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Machinery and Equipment [Member] | Maximum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Transportation Equipment [Member] | Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Transportation Equipment [Member] | Maximum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	8 years

Mergers, Acquisitions and Inv_3

Mergers, Acquisitions and Investment - Additional Information (Details) $ / shares in Units, shares in Millions, $ in Millions

Sep. 04, 2018USD ($)

Jan. 05, 2018USD ($)T

Oct. 20, 2017USD ($)

Aug. 01, 2017USD ($)

Jul. 17, 2017USD ($)T

Jun. 09, 2017USD ($)sharesT

Jun. 06, 2017USD ($)$ / sharesT

Mar. 13, 2017USD ($)T

Apr. 01, 2016USD ($)

Jan. 19, 2016USD ($)

Oct. 01, 2015USD ($)

Dec. 31, 2017USD ($)

Mar. 31, 2019T

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)shares

Apr. 30, 2017

Sep. 30, 2016USD ($)

Business Acquisition [Line Items]

Goodwill

$ 5,577.6

$ 5,528.3

$ 4,778.1

Finite-Lived Intangible Assets, Useful Life

16 years 7 months 6 days

Deferred payment, tax make-whole payment and unpaid (unreceived) working capital

$ (25)

4.6

3.5

Equity Method Investments

457.8

360.6

$ 328.9

Gross Carrying Amount

$ 4,318.3

4,227

Minimum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

1 year

Maximum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

40 years

Customer Relationships [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

16 years 8 months 12 days

Gross Carrying Amount

$ 4,123.7

$ 4,046.2

Schluter Acquisition [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 51.4

Business Acquisition, Purchase Price Allocation, Notes Payable and LT Debt

$ 7.5

Acquisition date

Sep. 4, 2018

Goodwill

$ 23.8

Property, plant, and equipment

27.5

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

21.5

Schluter Acquisition [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 9.1

Finite-Lived Intangible Assets, Useful Life

10 years 6 months

Plymouth Packaging [Member]

Business Acquisition [Line Items]

Acquisition date

Jan. 5, 2018

Goodwill

$ 58.7

Property, plant, and equipment

35.2

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

12.6

Business Acquisition, Cost of Acquired Entity, Preliminary Purchase Price

201.9

Cash and cash equivalents

3.1

Deferred payment, tax make-whole payment and unpaid (unreceived) working capital

$ 25.1

Annual tons of fully integrated containerboard used | T

60,000

Other long-term assets

$ 26.2

Plymouth Packaging [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 61.9

Finite-Lived Intangible Assets, Useful Life

13 years

Grupo Gondi Investment [Member]

Business Acquisition [Line Items]

Acquisition date

Apr. 1, 2016

Payments to Acquire Interest in Joint Venture

$ 108

$ 175

Equity Method Investment, Ownership Percentage

32.30%

25.00%

27.00%

Equity Method Investments

$ 300

Pre-Tax Non-Cash Gain in Connection with Investment in Joint Venture

$ 12.1

Hannapak [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 61.4

Acquisition date

Aug. 1, 2017

Goodwill

$ 25.3

Property, plant, and equipment

9.8

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

13.9

Cash and cash equivalents

$ 0.6

Hannapak [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

13 years

Gross Carrying Amount

$ 22.2

Island Container [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 84.7

Acquisition date

Jul. 17, 2017

Goodwill

$ 27.2

Property, plant, and equipment

5.4

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

$ 0.8

Expected Integration of Containerboard Into Corrugated Packaging Segment | T

80,000

Business acquisition, working capital settlement paid

1.2

Island Container [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

8 years 6 months

Gross Carrying Amount

$ 43

U.S. Corrugated [Member]

Business Acquisition [Line Items]

Acquisition date

Jun. 9, 2017

Goodwill

$ 110.5

Property, plant, and equipment

30

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

55.5

Cash and cash equivalents

$ 1.4

Increase in Containerboard Tons Due to the Vertical Integration of our Corrugated Packaging Segment | T

105,000

Increase in Containerboard Tons Due to Long-term Supply Contract | T

50,000

Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination

$ 193.7

Business acquisition, working capital settlement received

$ 3.4

Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares

2.4

2.4

Business Combination, Consideration Transferred, Equity Interests Issued and Issuable

$ 136.1

$ 136.1

U.S. Corrugated [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 77.8

Finite-Lived Intangible Assets, Useful Life

7 years 6 months

MPS [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 1,351.1

Business Acquisition, Purchase Price Allocation, Notes Payable and LT Debt

$ 929.1

Acquisition date

Jun. 6, 2017

Goodwill

$ 900.9

Property, plant, and equipment

469.9

Cash and cash equivalents

$ 47.5

Business Acquisition, Share Price | $ / shares

$ 18

Expected Integration of Paperboard Into Consumer Packaging Segment | T

225,000

Fair value of share-based awards issued in business combinations

$ 1.9

Total liabilities and noncontrolling interest assumed

1,561.6

MPS [Member] | Scenario, Forecast [Member]

Business Acquisition [Line Items]

Expected Integration of Paperboard Into Consumer Packaging Segment | T

100,000

MPS [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Gross Carrying Amount

$ 1,026.4

MPS [Member] | Customer Relationships [Member] | Minimum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

13 years

MPS [Member] | Customer Relationships [Member] | Maximum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

16 years

Star Pizza Acquisition [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 34.6

Acquisition date

Mar. 13, 2017

Goodwill

$ 2.2

Annual tons of fully integrated containerboard used | T

22,000

Business Acquisition, Working Capital Settlement

$ 0.7

Star Pizza Acquisition [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 24.8

Finite-Lived Intangible Assets, Useful Life

10 years

Packaging Acquisition [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 94.1

Business Acquisition, Purchase Price Allocation, Notes Payable and LT Debt

$ 1.3

Acquisition date

Jan. 19, 2016

Goodwill

$ 9.3

Property, plant, and equipment

55

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities

25.8

Cash and cash equivalents

1.7

Collection of Escrow Receivable in Business Combination

$ 3.5

Packaging Acquisition [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 10.5

Packaging Acquisition [Member] | Customer Relationships [Member] | Minimum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

9 years

Packaging Acquisition [Member] | Customer Relationships [Member] | Maximum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

15 years

SP Fiber [Member]

Business Acquisition [Line Items]

Business Acquisition, Cost of Acquired Entity, Purchase Price Net of Cash Acquired

$ 278.8

Business Acquisition, Purchase Price Allocation, Notes Payable and LT Debt

$ 13.7

Acquisition date

Oct. 1, 2015

Goodwill

$ 57.3

Property, plant, and equipment

324.8

Cash and cash equivalents

9.2

Total liabilities and noncontrolling interest assumed

$ 150.3

Percent Ownership in GPS

48.00%

Payment for Debt Owed by GPS

$ 36.5

SP Fiber [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles

$ 13.5

Finite-Lived Intangible Assets, Useful Life

20 years

Mergers, Acquisitions and Inv_4

Mergers, Acquisitions and Investment - Summary of Weighted Average Life and Allcocation to Intangible Asset Recognised in MPS Acquisition, Excluding Goodwill (Details) - MPS [Member] $ in Millions	Jun. 06, 2017USD ($)
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	14 years 4 months 24 days
Gross Carrying Amount	$ 1,026.4
Customer Relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	14 years 7 months 6 days
Gross Carrying Amount	$ 1,008.7
Trademarks and Tradenames [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	3 years
Gross Carrying Amount	$ 15.2
Photo Library [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	10 years
Gross Carrying Amount	$ 2.5

Restructuring and Other Costs -

Restructuring and Other Costs - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring And Related Activities [Abstract]
Restructuring and other costs	$ 105.4	$ 196.7	$ 366.4
Restructuring and other costs, noncash	$ 27	$ 86.6	$ 200.2

Restructuring and Other Costs_2

Restructuring and Other Costs - Schedule of Restructuring and Other Costs (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring And Related Activities [Abstract]
Restructuring									$ 39.5	$ 113.4	$ 294.9
Other									65.9	83.3	71.5
Restructuring and Other Costs	$ 40.3	$ 17.1	$ 31.7	$ 16.3	$ 38	$ 59.4	$ 18.3	$ 81	$ 105.4	$ 196.7	$ 366.4

Restructuring and Other Costs_3

Restructuring and Other Costs - Schedule of Restructuring Charges Related to Active Restructuring Initiatives (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		$ 39.5	$ 113.4	$ 294.9
Restructuring and Related Cost, Cost Incurred to Date		568.9
Restructuring and Related Cost, Expected Cost		572
Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		9.7	31.6	189.5
Restructuring and Related Cost, Cost Incurred to Date		256.3
Restructuring and Related Cost, Expected Cost		256.3
Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		9.9	47.3	69.5
Restructuring and Related Cost, Cost Incurred to Date		197.5
Restructuring and Related Cost, Expected Cost		198.3
Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		5.8	4.7	1.4
Restructuring and Related Cost, Cost Incurred to Date		14.5
Restructuring and Related Cost, Expected Cost		15
Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		4.2	6.1	19.4
Restructuring and Related Cost, Cost Incurred to Date		40.1
Restructuring and Related Cost, Expected Cost		41.9
Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		9.9	23.7	15.1
Restructuring and Related Cost, Cost Incurred to Date		60.5
Restructuring and Related Cost, Expected Cost		60.5
Corporate, Non-Segment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		5.6	19.6	44.1
Restructuring and Related Cost, Cost Incurred to Date		117.5
Restructuring and Related Cost, Expected Cost		117.5
Corporate, Non-Segment [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost			0.1	1.2
Restructuring and Related Cost, Cost Incurred to Date		1.4
Restructuring and Related Cost, Expected Cost		1.4
Corporate, Non-Segment [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		0.8	14.8	36.9
Restructuring and Related Cost, Cost Incurred to Date		100.6
Restructuring and Related Cost, Expected Cost		100.6
Corporate, Non-Segment [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		4.8	4.7	6
Restructuring and Related Cost, Cost Incurred to Date		15.5
Restructuring and Related Cost, Expected Cost		15.5
Corrugated Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		10.6	10.8	230.2
Restructuring and Related Cost, Cost Incurred to Date		316.6
Restructuring and Related Cost, Expected Cost		318.4
Corrugated Packaging [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		2.8	1.4	184.5
Restructuring and Related Cost, Cost Incurred to Date		211.5
Restructuring and Related Cost, Expected Cost		211.5
Corrugated Packaging [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		1.6	3.3	17.4
Restructuring and Related Cost, Cost Incurred to Date		42.2
Restructuring and Related Cost, Expected Cost		42.8
Corrugated Packaging [Member] | Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		3.1	1.9	0.3
Restructuring and Related Cost, Cost Incurred to Date		7.1
Restructuring and Related Cost, Expected Cost		7.1
Corrugated Packaging [Member] | Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		3.2	5.4	18.9
Restructuring and Related Cost, Cost Incurred to Date		36.7
Restructuring and Related Cost, Expected Cost		37.9
Corrugated Packaging [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		(0.1)	(1.2)	9.1
Restructuring and Related Cost, Cost Incurred to Date		19.1
Restructuring and Related Cost, Expected Cost		19.1
Consumer Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		20	78.4	10
Restructuring and Related Cost, Cost Incurred to Date		116.3
Restructuring and Related Cost, Expected Cost		117.6
Consumer Packaging [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		6.9	28.3	3.8
Restructuring and Related Cost, Cost Incurred to Date		41.6
Restructuring and Related Cost, Expected Cost		41.6
Consumer Packaging [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		7.2	26.4	4.6
Restructuring and Related Cost, Cost Incurred to Date		41
Restructuring and Related Cost, Expected Cost		41.2
Consumer Packaging [Member] | Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		2.7	2.8	1.1
Restructuring and Related Cost, Cost Incurred to Date		7.4
Restructuring and Related Cost, Expected Cost		7.9
Consumer Packaging [Member] | Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		1	0.7	0.5
Restructuring and Related Cost, Cost Incurred to Date		3.4
Restructuring and Related Cost, Expected Cost		4
Consumer Packaging [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	[1]	2.2	20.2
Restructuring and Related Cost, Cost Incurred to Date	[1]	22.9
Restructuring and Related Cost, Expected Cost	[1]	22.9
Land and Development [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		3.3	4.6	10.6
Restructuring and Related Cost, Cost Incurred to Date		18.5
Restructuring and Related Cost, Expected Cost		18.5
Land and Development [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost			1.8
Restructuring and Related Cost, Cost Incurred to Date		1.8
Restructuring and Related Cost, Expected Cost		1.8
Land and Development [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		0.3	$ 2.8	$ 10.6
Restructuring and Related Cost, Cost Incurred to Date		13.7
Restructuring and Related Cost, Expected Cost		13.7
Land and Development [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		3
Restructuring and Related Cost, Cost Incurred to Date		3
Restructuring and Related Cost, Expected Cost		$ 3
[1]	Includes a $17.6 million impairment of a customer relationship intangible in fiscal 2017 related to an exited product line.

Restructuring and Other Costs_4

Restructuring and Other Costs - Schedule of Restructuring Charges Related to Active Restructuring Initiatives (Parenthetical) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017USD ($)
Customer Relationships [Member] | Consumer Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 17.6

Restructuring and Other Costs_5

Restructuring and Other Costs - Schedule of Acquisition, Divestiture and Integration Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Acquisition costs	$ 38.2	$ 27.1	$ 8.9
Integration costs	22	41.2	59.8
Divestiture costs	0.3	9.8	0.5
Other total	65.9	83.3	71.5
Other Segments [Member]
Restructuring Cost And Reserve [Line Items]
Acquisition costs	38.2	27.1	8.9
Integration costs	27.4	46.4	62.1
Divestiture costs	0.3	9.8	0.5
Other total	$ 65.9	$ 83.3	$ 71.5

Restructuring and Other Costs_6

Restructuring and Other Costs - Schedule of Changes in Restructuring Accrual Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring And Other Costs [Abstract]
Accrual at beginning of fiscal year	$ 47.4	$ 44.8	$ 21.4
Accruals acquired in acquisition		3.5
Additional accruals	16.5	63.2	75.3
Payments	(29.8)	(53.3)	(51.9)
Adjustment to accruals	(1)	(10.8)
Foreign currency rate changes	(1.5)
Accrual at end of fiscal year	$ 31.6	$ 47.4	$ 44.8

Restructuring and Other Costs_7

Restructuring and Other Costs - Schedule of Reconciliation of Accruals and Charges (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring And Other Costs [Abstract]
Additional accruals and adjustments to accruals (see table above)									$ 15.5	$ 52.4	$ 75.3
Acquisition costs									38.2	27.1	8.9
Integration costs									22	41.2	59.8
Divestiture costs									0.3	9.8	0.5
Net property, plant and equipment									9.7	31.6	189.5
Severance and other employee costs									1.3	3.8	11.5
Equipment and inventory relocation costs									5.8	4.7	1.4
Facility carrying costs									4.2	6.1	19.5
Other costs									8.4	20
Restructuring and Other Costs	$ 40.3	$ 17.1	$ 31.7	$ 16.3	$ 38	$ 59.4	$ 18.3	$ 81	$ 105.4	$ 196.7	$ 366.4

Retirement Plans - Schedule of

Retirement Plans - Schedule of Allocation of Plan Assets - (Details) - Pension Plan [Member]	Sep. 30, 2018	Sep. 30, 2017
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	100.00%	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	100.00%	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Equity Securities [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	15.00%	15.00%
Defined Benefit Plan, Actual Plan Asset Allocations	14.00%	13.00%
Equity Securities [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	22.00%	24.00%
Defined Benefit Plan, Actual Plan Asset Allocations	23.00%	26.00%
Fixed Income Investments [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	75.00%	70.00%
Defined Benefit Plan, Actual Plan Asset Allocations	73.00%	73.00%
Fixed Income Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	70.00%	65.00%
Defined Benefit Plan, Actual Plan Asset Allocations	69.00%	64.00%
Short-term Investments [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	1.00%	1.00%
Defined Benefit Plan, Actual Plan Asset Allocations	3.00%	3.00%
Short-term Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	1.00%	1.00%
Defined Benefit Plan, Actual Plan Asset Allocations	2.00%	3.00%
Other Investments [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	9.00%	14.00%
Defined Benefit Plan, Actual Plan Asset Allocations	10.00%	11.00%
Other Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	7.00%	10.00%
Defined Benefit Plan, Actual Plan Asset Allocations	6.00%	7.00%

Retirement Plans - Additional I

Retirement Plans - Additional Information (Details) $ in Millions	Sep. 21, 2016USD ($)Number	Jan. 01, 2016	Mar. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Sep. 30, 2019	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Feb. 28, 2017USD ($)
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used, Minimum Outstanding Par Value of Bonds Used to Determine Future Discount Rate							$ 100
Pension lump sum settlement and retiree medical curtailment, net			$ 28.7					$ 32.6
Lump Sum Payment Related to Pension Settlement Made Out of Existing Plan Assets					$ 203.7			230.8
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate									4.04%	4.49%
Defined Benefit Plan, Increase in Funded Status										$ 73.2
Settlements				$ 27.1
Plan Assets Used to Settle Pension Obligations Plan by Purchasing Group Annuity Contracts from Prudential	$ 2,500
Retirement Benefits Payment Responsibility Movedto Prudential Owedto U. S. Retireesand Their Beneficiaries Number | Number	35,000
Pension risk transfer expense	$ 370.7								$ 370.7
Percentage Reduction of Overall U.S. Pension Obligations and Assets in Connection with Settlement	40.00%
Defined benefit plan, accumulated benefit obligation				5,390.7			$ 5,081.3	$ 5,390.7
Adjustment to RP-2014 table white collar males							10.00%	9.00%	6.00%
Adjustment to RP-2014 table blue collar males							14.00%	12.00%	10.00%
Adjustment to RP-2014 tables white collar females							11.00%	11.00%	12.00%
Adjustment to RP-2014 tables blue collar female							10.00%	9.00%	19.00%
Defined benefit plan, effect of one percentage point increase on accumulated postretirement benefit obligation							$ 7
Defined benefit plan, effect of one percentage point increase on service and interest cost components							0
Defined benefit plan, effect of one percentage point decrease on accumulated postretirement benefit obligation							6
Defined benefit plan, effect of one percentage point decrease on service and interest cost components							1
Multiemployer Plans, Withdrawal Obligation				$ 60.1			$ 247.8	$ 60.1
Periods of Payments Used to Calculate Withdrawal Liability in Connection with PIUMPF Withdrawal							20 years
Credit Adjusted Risk-Free Rate Used to Calculate Withdrawal Liability in Connection with PIUMPF Withdrawal							3.83%
Multiemployer Plan, Accrual Related to a Partial Plan Withdrawal							$ 6	1.9	$ 2.1
Percentage of Employees Covered by Collective Bargaining Agreements							43.00%
Percentage of Employees Working Under Expired Collective Bargaining Agreement							8.00%
Percentage of Employees Covered By Collective Bargaining Agreements Expiring in One Year							6.00%
Defined Contribution Plan Employer Contribution on Basic Salary, Maximum, High End of Range							7.50%
Defined Contribution Plan Employer Contribution on Basic Salary, Automatic Matching Contribution							2.50%
Defined Contribution Plan Employer Contribution on Basic Salary, Employees Covered under a CBA, Maximum, Low End of Range							3.00%
Defined Contribution Plan Employer Contribution on Basic Salary, Employees Covered under a CBA, Maximum, High End of Range							4.00%
Defined Contribution Plan, Cost							$ 113.7	$ 104.1	$ 86.5
Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation							180
Central States, Southeast and Southwest Areas Pension Fund [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation							$ 4.2
Maximum [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of surcharge on contribution		15.00%
Defined Contribution Plan Employer Contribution on Basic Salary, Matching Contribution							5.00%
Minimum [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of surcharge on contribution		10.00%
Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Certified Zone Status [Fixed List]							Red
Pace Industry Union Management Pension Fund [Member] | Maximum [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions exceeded 5% of total plan contributions							5.00%
Green Zone [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage funded in zone							At least 80 percent
Multiemployer Plans, Certified Zone Status [Fixed List]							Green
Yellow Zone [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage funded in zone							Between 65 and less than 80 percent
Multiemployer Plans, Certified Zone Status [Fixed List]							Yellow
Red Zone [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage funded in zone							Less than 65 percent
Multiemployer Plans, Certified Zone Status [Fixed List]							Red
Pension Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year							$ 22
Pension Plan [Member] | Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Certified Zone Status [Fixed List]								Red
Pension Plan [Member] | United States [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets							6.50%	6.50%	5.88%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.09%			4.50%	4.09%
Settlements							$ 0	$ 229.3
Pension Plan [Member] | United States [Member] | Non-Qualified Plans [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, plan with benefit obligation in excess of plan assets, benefit obligation							197
Defined benefit plan, pension plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation							195.3
Defined benefit plan, plan with benefit obligation in excess of plan assets, fair value of plan assets							$ 29.5
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets							4.98%	6.03%	6.34%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				3.26%			3.42%	3.26%
Settlements							$ 5.5	$ 0.4
Pension Plan [Member] | Scenario, Forecast [Member] | United States [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets						6.50%
Pension Plan [Member] | Scenario, Forecast [Member] | Foreign Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets						4.69%
Other Pension, Postretirement and Supplemental Plans [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and other postretirement plans, assets							174.2
Pension and other postretirement plans, liabilities							$ 178.1

Retirement Plans - Schedule o_2

Retirement Plans - Schedule of Weighted-Average Assumptions Used to Measure Benefit Plan Obligations (Details)	Sep. 30, 2018	Sep. 30, 2017	Feb. 28, 2017	Sep. 30, 2016
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate			4.49%	4.04%
Pension Plan [Member] | United States [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.50%	4.09%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	3.00%	3.00%
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.42%	3.26%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	2.67%	3.17%
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.50%	4.09%
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	6.61%	6.51%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		7.37%

Retirement Plans - Schedule o_3

Retirement Plans - Schedule of Changes in Benefit Obligations (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Settlements	$ (27.1)
Prepaid pension asset	368	$ 420	$ 368
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost		44.8	45.1	$ 51.4
Interest cost		204.6	197.8	310.3
Special termination benefits		0	(12.5)	(18.4)
Pension Plan [Member] | United States [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year		3,941.9	4,231.7
Service cost		36.7	38
Interest cost		157.7	165.2
Amendments		9.3	3.5
Actuarial gain		(186.8)	(149.1)
Plan participant contributions		0	0
Special termination benefits		0	12.5
Benefits paid		(175.3)	(141.4)
Business combinations		0	0
Curtailments		0	0
Settlements		0	(229.3)
Foreign currency rate changes		0	0
Other adjustments		0	10.8
Business divestitures		0	0
Benefit obligation at end of fiscal year	3,941.9	3,783.5	3,941.9	4,231.7
Fair value of plan assets at beginning of fiscal year		4,107.9	4,301.5
Actual (loss) gain on plan assets		(24.9)	104.2
Employer contributions		13.5	15.3
Plan participant contributions		0	0
Benefits paid		(175.3)	(141.4)
Business combinations		0	0
Settlements		0	(229.3)
Business divestitures		0	0
Foreign currency rate changes		0	0
Other adjustments		0	57.6
Fair value of plan assets at end of fiscal year	4,107.9	3,921.2	4,107.9	4,301.5
Over (under) funded status	166	137.7	166
Prepaid pension asset	340.4	305.7	340.4
Other current liability	(9.3)	(10.1)	(9.3)
Accrued pension, postretirement and other long-term benefits	(165.1)	(157.9)	(165.1)
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year		1,502.2	925.2
Service cost		8	7.1
Interest cost		46.9	32.6
Amendments		0	0
Actuarial gain		(90.3)	(57.6)
Plan participant contributions		2.5	1.7
Special termination benefits		0	0
Benefits paid		(82.8)	(65.1)
Business combinations		3.5	621
Curtailments		(0.7)	0
Settlements		(5.5)	(0.4)
Foreign currency rate changes		(43.6)	65.1
Other adjustments		0	0
Business divestitures		0	(27.4)
Benefit obligation at end of fiscal year	1,502.2	1,340.2	1,502.2	925.2
Fair value of plan assets at beginning of fiscal year		1,414.7	774.1
Actual (loss) gain on plan assets		39.9	2.4
Employer contributions		24.2	19.2
Plan participant contributions		2.5	1.7
Benefits paid		(82.8)	(65.1)
Business combinations		0.7	622.1
Settlements		(5.5)	(0.4)
Business divestitures		0	(0.7)
Foreign currency rate changes		(43.5)	61.4
Other adjustments		0	0
Fair value of plan assets at end of fiscal year	1,414.7	1,350.2	1,414.7	774.1
Over (under) funded status	(87.5)	10	(87.5)
Prepaid pension asset	27.6	114.3	27.6
Other current liability	(0.8)	(0.9)	(0.8)
Accrued pension, postretirement and other long-term benefits	(114.3)	(103.4)	(114.3)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost		1.5	0.9	2.3
Interest cost		7.9	7.4	8.1
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year		98.1	90.7
Service cost		0.7	0.1
Interest cost		3.9	3.3
Amendments		(1.4)	(3.4)
Actuarial gain		(2.5)	14.1
Benefits paid		(7.8)	(8)
Business combinations		0	1.3
Curtailments		0	0
Foreign currency rate changes		0	0
Business divestitures		0	0
Benefit obligation at end of fiscal year	98.1	91	98.1	90.7
Fair value of plan assets at beginning of fiscal year		0	0
Employer contributions		7.8	8
Plan participant contributions		0	0
Benefits paid		(7.8)	(8)
Fair value of plan assets at end of fiscal year	0	0	0	0
Over (under) funded status	(98.1)	(91)	(98.1)
Other current liability	(9.8)	(8.8)	(9.8)
Accrued pension, postretirement and other long-term benefits	(88.3)	(82.2)	(88.3)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year		68.1	62.6
Service cost		0.8	0.8
Interest cost		4	4.1
Amendments		0	(1)
Actuarial gain		(5.2)	0.4
Benefits paid		(2.6)	(2.7)
Business combinations		0	2
Curtailments		(2.1)	(0.3)
Foreign currency rate changes		(7.5)	2.6
Business divestitures		0	(0.4)
Benefit obligation at end of fiscal year	68.1	55.5	68.1	62.6
Fair value of plan assets at beginning of fiscal year		0	0
Employer contributions		2.6	2.7
Plan participant contributions		0	0
Benefits paid		(2.6)	(2.7)
Fair value of plan assets at end of fiscal year	0	0	0	$ 0
Over (under) funded status	(68.1)	(55.5)	(68.1)
Other current liability	(3)	(2.9)	(3)
Accrued pension, postretirement and other long-term benefits	$ (65.1)	$ (52.6)	$ (65.1)

Retirement Plans - Schedule o_4

Retirement Plans - Schedule of Amounts in Accumulated Other Comprehensive (Income) Loss (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 631.2	$ 547.3
Prior service cost (credit)	32.3	27.6
Total accumulated other comprehensive loss (income)	663.5	574.9
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	105.6	173.9
Prior service cost (credit)	0.3	0.4
Total accumulated other comprehensive loss (income)	105.9	174.3
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(11.2)	(9.1)
Prior service cost (credit)	(11.3)	(13.9)
Total accumulated other comprehensive loss (income)	(22.5)	(23)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(3.8)	4.2
Prior service cost (credit)	(1)	(1.4)
Total accumulated other comprehensive loss (income)	$ (4.8)	$ 2.8

Retirement Plans - Schedule o_5

Retirement Plans - Schedule of Amounts Recognized in Other Comprehensive (Income) Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during period	$ 29	$ (34.1)	$ 354
Amortization and settlement recognition of net actuarial (loss) gain	(20.9)	(56.4)	(379.7)	[1]
Prior service cost (credit) arising during period	7.8	(1)	(2.3)
Amortization of prior service (cost) credit	(0.3)	0.4	(1.8)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during period	38.7	(48.8)	355.4
Amortization and settlement recognition of net actuarial (loss) gain	(20.6)	(57.7)	(381.6)
Prior service cost (credit) arising during period	9.3	3.4	1.5
Amortization of prior service (cost) credit	(4.7)	(4.1)	(3.9)
Net amount recognized in other comprehensive (income) loss	22.7	(107.2)	(28.6)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during period	(9.7)	14.7	(1.4)
Amortization and settlement recognition of net actuarial (loss) gain	(0.3)	1.3	1.9
Prior service cost (credit) arising during period	(1.5)	(4.4)	(3.8)
Amortization of prior service (cost) credit	4.4	4.5	2.1
Net amount recognized in other comprehensive (income) loss	$ (7.1)	$ 16.1	$ (1.2)
[1]	Includes pension risk transfer expense.

Retirement Plans - Schedule o_6

Retirement Plans - Schedule of Retirement Plans Amounts Recognized in Consolidated Statement of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 44.8	$ 45.1	$ 51.4
Interest cost	204.6	197.8	310.3
Expected return on plan assets	(328.4)	(313.1)	(412.3)
Amortization of net actuarial loss (gain)	21.2	25.4	11
Amortization of prior service cost (credit)	4.7	4.1	3.9
Curtailment gain	(0.6)	0	(1.6)
Settlement (gain) loss	(0.5)	32.7	370.7
Special termination benefits	0	12.5	18.4
Company defined benefit plan (income) expense	(54.2)	4.5	351.8
Multiemployer and other plans	1.4	4.7	5.8
Net pension (income) cost	(52.8)	9.2	357.6
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.5	0.9	2.3
Interest cost	7.9	7.4	8.1
Amortization of net actuarial loss (gain)	0.3	(1.3)	(2)
Amortization of prior service cost (credit)	(4.4)	(4.5)	(2.1)
Curtailment gain	(0.1)	(0.3)	0
Net pension (income) cost	$ 5.2	$ 2.2	$ 6.3

Retirement Plans - Schedule o_7

Retirement Plans - Schedule of Weighted-Average Assumptions Used in Calculation of Benefit Plan Expense (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.09%	4.30%	4.70%
Defined Benefit Plan, Assumptions Used Caclulating Net Periodic Cost, Rate of Compensation Increase	3.00%	3.00%	2.50%
Expected long-term rate of return on plan assets	6.50%	6.50%	5.88%
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.26%	3.08%	3.89%
Defined Benefit Plan, Assumptions Used Caclulating Net Periodic Cost, Rate of Compensation Increase	2.65%	3.09%	3.10%
Expected long-term rate of return on plan assets	4.98%	6.03%	6.34%
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.09%	4.04%	4.70%
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	6.51%	6.64%	6.84%
Defined Benefit Plan, Assumptions Used Caclulating Net Periodic Cost, Rate of Compensation Increase	7.37%	3.14%	3.10%

Retirement Plans - Schedule o_8

Retirement Plans - Schedule of Estimated Losses Amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost (Details) $ in Millions	Sep. 30, 2018USD ($)
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of Loss (Gain), Next Fiscal Year	$ 22.7
Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	5.2
Expected Amortization, Next Fiscal Year	27.9
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of Loss (Gain), Next Fiscal Year	5.3
Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	0.1
Expected Amortization, Next Fiscal Year	5.4
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of Loss (Gain), Next Fiscal Year	(1.1)
Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	(2.6)
Expected Amortization, Next Fiscal Year	(3.7)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of Loss (Gain), Next Fiscal Year	(0.4)
Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	(0.2)
Expected Amortization, Next Fiscal Year	$ (0.6)

Retirement Plans - Schedule o_9

Retirement Plans - Schedule of Estimated Benefit Payments (Details) $ in Millions	Sep. 30, 2018USD ($)
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2,019	$ 209.1
Fiscal 2,020	218.6
Fiscal 2,021	223
Fiscal 2,022	231.7
Fiscal 2,023	218.5
Fiscal Years 2024 – 2028	1,168.9
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2,019	80.1
Fiscal 2,020	80.9
Fiscal 2,021	79.8
Fiscal 2,022	80
Fiscal 2,023	80.2
Fiscal Years 2024 – 2028	398.9
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2,019	9.3
Fiscal 2,020	8.2
Fiscal 2,021	7.8
Fiscal 2,022	7.4
Fiscal 2,023	7.1
Fiscal Years 2024 – 2028	31.4
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2,019	2.9
Fiscal 2,020	3
Fiscal 2,021	3.1
Fiscal 2,022	3.2
Fiscal 2,023	3.3
Fiscal Years 2024 – 2028	$ 19.1

Retirement Plans - Summary of P

Retirement Plans - Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions		Sep. 30, 2018	Sep. 30, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at NAV		$ 2,191.6	$ 2,378.7
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		5,271.4	5,522.6
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value Investments		3,079.8	3,143.9
Assets measured at NAV	[1]	2,191.6	2,378.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value Investments		480.4	504.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value Investments		2,599.4	2,639.3
Fair Value, Measurements, Recurring [Member] | US Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[2]	165.5	136.7
Fair Value, Measurements, Recurring [Member] | US Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[2]	165.5	136.6
Fair Value, Measurements, Recurring [Member] | US Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[2]		0.1
Fair Value, Measurements, Recurring [Member] | Non US Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[2]	8.2	40
Fair Value, Measurements, Recurring [Member] | Non US Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[2]	8.2	40
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[3]	435.8	452
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[3]	435.8	452
Fair Value, Measurements, Recurring [Member] | Non-US government securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	127.5	130
Fair Value, Measurements, Recurring [Member] | Non-US government securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	127.5	130
Fair Value, Measurements, Recurring [Member] | US Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	1,493.6	1,515.4
Fair Value, Measurements, Recurring [Member] | US Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	108.4	92.3
Fair Value, Measurements, Recurring [Member] | US Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	1,385.2	1,423.1
Fair Value, Measurements, Recurring [Member] | Non-US corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	380.8	373.7
Fair Value, Measurements, Recurring [Member] | Non-US corporate bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	49.3	51.1
Fair Value, Measurements, Recurring [Member] | Non-US corporate bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]	331.5	322.6
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]		0.1
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[4]		0.1
Fair Value, Measurements, Recurring [Member] | Other Fixed Income Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[5]	319.4	311.4
Fair Value, Measurements, Recurring [Member] | Other Fixed Income Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[5]	319.4	311.4
Fair Value, Measurements, Recurring [Member] | Short-term Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[6]	149	184.6
Fair Value, Measurements, Recurring [Member] | Short-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[6]	$ 149	$ 184.6
[1]	Investments that are measured at net asset value (“NAV”) (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy.
[2]	Equity securities are comprised of the following investment types: (i) common stock, (ii) preferred stock and (iii) equity exchange traded funds. Level 1 investments in common and preferred stocks and exchange traded funds are valued using quoted market prices multiplied by the number of shares owned.
[3]	U.S. government securities include treasury and agency debt. These investments are valued using broker quotes in an active market.
[4]	The level 1 non-U.S. government securities investment is an exchange traded fund valued using quoted market prices. The level 1 U.S. corporate bonds category is primarily comprised of U.S. dollar denominated investment grade securities and valued using quoted market prices. Level 2 investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads, and/or other applicable reference data.
[5]	Other fixed income is comprised of municipal and asset-backed securities. Investments are valued utilizing a market approach that includes various valuation techniques and sources, such as broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer spreads and/or other applicable reference data.
[6]	Short-term investments are valued at $1.00/unit, which approximates fair value. Amounts are generally invested in interest-bearing accounts.

Retirement Plans - Summary of_2

Retirement Plans - Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis (Parenthetical) (Details)	12 Months Ended
	Sep. 30, 2018$ / Unit
Retirement Plans [Abstract]
Short-term investments per units	1

Retirement Plans - Summary of A

Retirement Plans - Summary of Assets Measured at Fair Value Based on NAV Per Share (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plans, Fair Value of Plan Assets		$ 2,191.6		$ 2,378.7
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments		75.3		98.8
Hedge Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plans, Fair Value of Plan Assets	[1]	$ 47.9		$ 64.2
Hedge Funds [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	[1]	30 days		91 days
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plans, Fair Value of Plan Assets		$ 1,092.9	[1]	$ 1,207.6	[2]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments		$ 75.3	[1]	$ 98.8	[2]
Equity Securities [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period		60 days	[1]	60 days	[2]
Fixed Income Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plans, Fair Value of Plan Assets	[3]	$ 1,050.8		$ 1,106.9
Fixed Income Securities [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	[3]	10 days		10 days
[1]	Hedge fund investments are primarily made through shares of limited partnerships or similar structures. Hedge funds are typically valued monthly by third-party administrators that have been appointed by the funds’ general partners. Hedge funds have been valued using NAV as a practical expedient.
[2]	Commingled fund investments are valued at the net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled funds have been valued using NAV as a practical expedient.
[3]	Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their net asset value per share multiplied by the number of shares held. The determination of net asset value for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. Commingled debt funds have been valued using NAV as a practical expedient.

Retirement Plans - Schedule _10

Retirement Plans - Schedule of Health Care Cost Trend Rates (Details) - Other Postretirement Benefits Plan [Member]	12 Months Ended
	Sep. 30, 2018
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	6.03%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.43%
Year the rate reaches the ultimate trend rate	2,037
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	5.51%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	5.51%
Year the rate reaches the ultimate trend rate	2,018

Retirement Plans - Schedule _11

Retirement Plans - Schedule of Multiemployer Plans (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pace Industry Union Management Pension Fund [Member]
Schedule Of Multi Employer Plans [Line Items]
Multiemployer Plans, Certified Zone Status		Red
Pension Plan [Member]
Schedule Of Multi Employer Plans [Line Items]
Multiemployer and Other Plans, Period Contributions	[1],[2]	$ 1.4	$ 5.1	$ 4.5
Pension Plan [Member] | Pace Industry Union Management Pension Fund [Member]
Schedule Of Multi Employer Plans [Line Items]
Entity Tax Identification Number		116,166,763
Multiemployer Plan Number		1
Multiemployer Plans, Certified Zone Status			Red
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		Implemented
Surcharge imposed?		Yes
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, First		Sep. 30, 2020
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, Last		Jun. 25, 2023
Multiemployer and Other Plans, Period Contributions	[1],[3]	$ 0.9	$ 3.5	3.3
Pension Plan [Member] | Other Funds [Member]
Schedule Of Multi Employer Plans [Line Items]
Multiemployer and Other Plans, Period Contributions	[1],[3]	$ 0.5	$ 1.6	$ 1.2
[1]	Contributions represent the amounts contributed to the plan during the fiscal year.
[2]	Two additional MEPPs in which we participate have been certified as critical and declining.
[3]	Our contributions for fiscal 2017 and 2016 exceeded 5% of total plan contributions. Although the plan data for fiscal 2018 is not yet available, we do not expect to continue to exceed 5% of total plan contributions due to our submission of notification to withdraw from PIUMPF.

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
United States					$ 736.7	$ 481.9	$ (25.1)
Foreign					298.1	375.7	269.7
Income from continuing operations before income taxes					1,034.8	857.6	244.6
Deferred income taxes:
Total deferred (benefit) expense					(1,069.4)	(20.4)	(160.9)
Total income tax (benefit) expense	$ (95.4)	$ (84.5)	$ (18.8)	$ 1,073.2	(874.5)	159	89.8
Continuing Operations [Member]
Current income taxes:
Federal					83	80.8	98.3
State					26.8	3.3	12.8
Foreign					86.6	95.3	87
Total current expense					196.4	179.4	198.1
Deferred income taxes:
Federal					(1,108.6)	15.2	(131.5)
State					53.2	(22.8)	6.9
Foreign					(15.5)	(12.8)	16.3
Total deferred (benefit) expense					(1,070.9)	(20.4)	(108.3)
Total income tax (benefit) expense					$ (874.5)	$ 159	$ 89.8

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	Dec. 22, 2017	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Provisional Estimate of Benefit (Expense) Impact on Remeasurement of Deferred Tax Balances in Connection with December 22, 2017 Income Tax Legislation		$ 36.3	$ 1,086.9	$ 1,215.9
Provisional Amount for One-time Transition Tax Liability in Connection with December 22, 2017 Income Tax Legislation				95.4
Provisional Amount for One-time Transition Tax Liability in Connection with December 22, 2017 Income Tax Legislation, Net of a Release of a Previously Recorded Outside Basis Difference				87.1
Operating Loss Carryforwards				13.3	$ 61.2
Deferred income tax assets:
State net operating loss carryforwards				78.4	70.6
Federal and foreign net operating loss carryforwards				188.7	204.1
Deferred income tax liabilities:
Operating Loss Carryforwards				13.3	61.2
Undistributed Foreign Earnings				1,500
Balance at end of fiscal year				127.1	148.9	$ 166.8	$ 106.6
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				108.7	138
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued				70.4	81.7
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense				5.8	7.4	$ 2.9
Decrease in Unrecognized Tax Benefits is Reasonably Possible				5.5
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards				1,676	1,885
Deferred income tax assets:
State net operating loss carryforwards				78.4	70.6
Tax Credit Carryforward, Deferred Tax Asset				64.8	54.4
Tax credit carryforward, valuation allowance				56.1	47.3
Deferred income tax liabilities:
Operating Loss Carryforwards				1,676	1,885
Operating Loss Carryforwards, Valuation Allowance				7.8	15.9
Foreign Country [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards				698.4	673.7
Deferred income tax assets:
Federal and foreign net operating loss carryforwards				185.8	182.6
Deferred income tax liabilities:
Operating Loss Carryforwards				698.4	673.7
Operating Loss Carryforwards, Valuation Allowance				161.5	149.6
Alternative Minimum Tax Credits [Member]
Deferred income tax liabilities:
Tax credit carryforward				14.7	$ 132.2
Research Tax Credit Carryforward [Member]
Deferred income tax liabilities:
Tax credit carryforward				0
General Business Tax Credit Carryforward [Member]
Deferred income tax liabilities:
Tax credit carryforward				$ 0
Minimum [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Oct. 1, 2031
Minimum [Member] | State and Local Jurisdiction [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Oct. 1, 2020
Tax Credit Carryforward, Years to Expiration				5 years
Minimum [Member] | Foreign Country [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Oct. 1, 2020
Maximum [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Sep. 30, 2038
Maximum [Member] | State and Local Jurisdiction [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Sep. 30, 2038
Tax Credit Carryforward, Years to Expiration				10 years
Maximum [Member] | Foreign Country [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Sep. 30, 2038

Income Taxes Effective Tax Rate

Income Taxes Effective Tax Rate Reconciliation (Details)		Dec. 22, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statutory federal tax rate		21.00%
Continuing Operations [Member]
Statutory federal tax rate			24.50%	35.00%	35.00%
Foreign rate differential			0.60%	(4.90%)	(5.50%)
Adjustment and resolution of federal, state and foreign tax uncertainties			0.90%	(0.30%)	0.20%
State taxes, net of federal benefit			4.30%	3.30%	4.90%
Tax Act	[1]		(109.10%)
Excess tax benefit related to stock compensation			(0.80%)
Research and development and other tax credits, net of valuation allowances and reserves			(0.50%)	(0.80%)	(6.10%)
Income attributable to noncontrolling interest			(0.10%)	0.40%	0.80%
Domestic manufacturer’s deduction			(1.80%)	(2.00%)	(4.40%)
Sale of HH&B				(5.00%)
U.S. legal entity restructuring				(3.30%)
Change in valuation allowance			(1.80%)	(3.30%)	6.30%
Nondeductible transaction costs				1.00%	0.40%
Contribution of assets to Grupo Gondi joint venture					3.40%
Nontaxable increased cash surrender value			(0.80%)	(1.50%)	(4.60%)
Withholding taxes			0.50%	0.40%	2.00%
Brazilian net worth deduction			(0.90%)	(0.80%)	(2.00%)
Other, net			0.50%	0.30%	6.30%
Effective tax rate			(84.50%)	18.50%	36.70%
[1]	The primary components are a $1,215.9 million benefit from the remeasurement of our net U.S. deferred tax liability and a one-time transition tax liability of $95.4 million or $87.1 million net of the release of a previously recorded outside basis difference

Income Taxes Effective Tax Ra_2

Income Taxes Effective Tax Rate Reconciliation (Parenthetical) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Income Tax Disclosure [Abstract]
Benefit from the remeasurement of our net U.S. deferred tax liability	$ 1,215.9
One-time transition liability	95.4
Tax Cuts and Jobs Act Of 2017 one-time transition liability net of the release of a previously recorded outside basis difference	$ 87.1

Income Taxes Deferred Taxes (De

Income Taxes Deferred Taxes (Details) - USD ($) $ in Millions		Sep. 30, 2018	Sep. 30, 2017
Deferred income tax assets:
Accruals and allowances		$ 22.1	$ 40.6
Employee related accruals and allowances		213.2	265.1
State net operating loss carryforwards		78.4	70.6
State credit carryforwards, net of federal benefit		64.8	54.4
U.S. and foreign tax credit carryforwards		14.7	135.9
Federal and foreign net operating loss carryforwards		188.7	204.1
Restricted stock and options		46.7	81
Other		45.3	32.8
Deferred Tax Assets, Gross		673.9	884.5
Deferred income tax liabilities:
Property, plant and equipment		1,509.7	2,154.1
Deductible intangibles and goodwill		698.1	1,091.4
Inventory reserves		168.6	236.1
Deferred gain		258.8	405.2
Pension obligations		60.1	90.8
Basis difference in joint ventures		35.5	57.1
Other			8.3
Deferred Tax Liabilities, Gross		2,730.8	4,043
Valuation allowances		229.4	219.1
Net deferred income tax liability		2,286.3	3,377.6
Long-term deferred tax asset	[1]	35.2	32.6
Deferred income taxes		2,321.5	3,410.2
Net deferred income tax liability		$ 2,286.3	$ 3,377.6
[1]	The long-term deferred tax asset is presented in Other assets on the consolidated balance sheets.

Income Taxes Valuation Allowanc

Income Taxes Valuation Allowance Against Deferred Tax Assets (Details) - Valuation Allowance of Deferred Tax Assets [Member] - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Movement in Deferred Tax Asset Valuation Allowance [Roll Forward]
Balance at beginning of fiscal year		$ 219.1	$ 177.2	$ 100.2
Increases		50.8	54.3	24.8
Allowances related to purchase accounting	[1]	0.1	12.4	63
Reductions		(40.6)	(24.8)	(10.8)
Balance at end of fiscal year		$ 229.4	$ 219.1	$ 177.2
[1]	Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition.

Income Taxes Unrecognized Tax B

Income Taxes Unrecognized Tax Benefit (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of fiscal year		$ 148.9	$ 166.8	$ 106.6
Additions related to purchase accounting	[1]	3.4	7.7	16.5
Additions for tax positions taken in current year		3.1	5	30.3
Additions for tax positions taken in prior fiscal years		18	15.2	20.6
Reductions for tax positions taken in prior fiscal years		(5.3)	(25.6)	(9.7)
Reductions due to settlement	[2]	(29.4)	(14.1)	(1.3)
(Reductions) additions for currency translation adjustments		(9.6)
(Reductions) additions for currency translation adjustments			2	7
Reductions as a result of a lapse of the applicable statute of limitations		(2)	(8.1)	(3.2)
Balance at end of fiscal year		$ 127.1	$ 148.9	$ 166.8
[1]	Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition. Adjustments in fiscal 2016 relate to the Combination and the SP Fiber Acquisition.
[2]	Amounts in fiscal 2018 relate to the settlement of state audit examinations and federal and state amended returns filed related to affirmative adjustments for which a there was a reserve. Amounts in fiscal 2017 relate to the settlement of federal and state audit examinations with taxing authorities

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)segment	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Pre-Tax Inventory Step-Up	$ 1	$ 26.5	$ 8.1
Corrugated Packaging [Member]
Segment Reporting Information [Line Items]
Pre-Tax Inventory Step-Up	1	1.4	3.4
Corrugated Packaging [Member] | Grupo Gondi Investment [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	133.9	76.2
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Amortizable Portion	$ 62.1	59.2
Corrugated Packaging [Member] | Grupo Gondi Investment [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Lives of Underlying Assets	10 years
Corrugated Packaging [Member] | Grupo Gondi Investment [Member] | Maximum [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Lives of Underlying Assets	15 years
Consumer Packaging [Member]
Segment Reporting Information [Line Items]
Pre-Tax Inventory Step-Up		$ 25.1	$ 4.7

Segment Information - Schedule

Segment Information - Schedule of Revenue from External Customers, Segment Income and Long-Lived Assets, by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Revenues from External Customers, Segment Income and Long-Lived Assets [Line Items]
Net sales	$ 4,236.6	$ 4,137.5	$ 4,017	$ 3,894	$ 4,060.6	$ 3,695.6	$ 3,656.3	$ 3,447.2	$ 16,285.1	$ 14,859.7	$ 14,171.8
Foreign Operations [Member]
Revenues from External Customers, Segment Income and Long-Lived Assets [Line Items]
Net sales									3,236.7	2,621.2	2,426.6
Segment income (loss)									360.7	260.1	226.1
Long-Lived Assets	$ 1,400.2				$ 1,558.3				$ 1,400.2	$ 1,558.3	$ 1,341.5
Percentage of Net Sales to Unaffiliated Customers									19.90%	17.60%	17.10%
Percentage of Segment Income									21.40%	21.80%	18.40%
Percentage of Long-Lived Assets	15.40%				17.10%				15.40%	17.10%	14.40%

Segment Information - Certain O

Segment Information - Certain Operating Data for Segments (Details) - USD ($) $ in Millions	Sep. 21, 2016	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net sales		$ 4,236.6	$ 4,137.5	$ 4,017	$ 3,894	$ 4,060.6	$ 3,695.6	$ 3,656.3	$ 3,447.2	$ 16,285.1	$ 14,859.7	$ 14,171.8
Multiemployer pension withdrawals			(4.2)		(180)					(184.2)
Pension risk transfer expense	$ (370.7)											(370.7)
Pension lump sum settlement						(3.9)		(28.7)			(32.6)
Land and Development impairments		(2.6)	(1.7)		(27.6)	(4)		(42.7)		(31.9)	(46.7)
Restructuring and other costs		(40.3)	(17.1)	(31.7)	(16.3)	(38)	(59.4)	(18.3)	$ (81)	(105.4)	(196.7)	(366.4)
Interest expense, net										(293.8)	(222.5)	(212.5)
Gain on extinguishment of debt		(0.1)	$ 0.9	$ 0.1	$ (1)	(0.1)	2	$ (0.1)		(0.1)	1.8	2.7
Other income, net										12.7	11.5	14.4
Gain on sale of HH&B						2.2	$ 190.6				192.8
Income from continuing operations before income taxes										1,034.8	857.6	244.6
Identifiable assets		25,360.5				25,089				25,360.5	25,089	23,038.2
Goodwill		5,577.6				5,528.3				5,577.6	5,528.3	4,778.1
Depreciation, depletion and amortization										1,252.2	1,112.1	1,141.9
Capital expenditures										999.9	778.6	796.7
Investment in unconsolidated entities		457.8				360.6				457.8	360.6	328.9
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										16,537.2	15,104.6	14,376.4
Segment income (loss)										1,685	1,193.5	1,226.2
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales										252.1	244.9	204.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Multiemployer pension withdrawals										(184.2)	0	0
Pension risk transfer expense										0	0	(370.7)
Pension lump sum settlement										0	(32.6)	0
Land and Development impairments										(31.9)	(46.7)	0
Non-allocated expenses										(47.5)	(43.5)	(49.1)
Interest expense, net										(293.8)	(222.5)	(212.5)
Gain on extinguishment of debt										(0.1)	1.8	2.7
Other income, net										12.7	11.5	14.4
Gain on sale of HH&B										0	192.8	0
Corrugated Packaging [Member]
Segment Reporting Information [Line Items]
Identifiable assets		10,678.5				10,537.7				10,678.5	10,537.7	10,046
Goodwill		1,890.9				1,865.7				1,890.9	1,865.7	1,722.5	$ 1,667.5
Depreciation, depletion and amortization										676.8	597.9	576.2
Capital expenditures										647.8	492.1	490.1
Investment in unconsolidated entities		435.7				321.1				435.7	321.1	281.2
Corrugated Packaging [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										9,103.4	8,408.3	7,868.5
Segment income (loss)										1,207.9	753.9	739.9
Corrugated Packaging [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales										161.6	155.8	136.2
Corrugated Packaging [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										8,941.8	8,252.5	7,732.3
Consumer Packaging [Member]
Segment Reporting Information [Line Items]
Identifiable assets		11,902.2				11,877.8				11,902.2	11,877.8	10,122.5
Goodwill		3,686.7				3,662.6				3,686.7	3,662.6	3,055.6	$ 2,979.6
Depreciation, depletion and amortization										569.3	508.2	498.9
Capital expenditures										317.8	265.8	244.9
Investment in unconsolidated entities		21.7				24.7				21.7	24.7	22.2
Consumer Packaging [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										7,291.4	6,452.5	6,388.1
Segment income (loss)										454.6	425.8	481.7
Consumer Packaging [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales										90.5	89.1	68.4
Consumer Packaging [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										7,200.9	6,363.4	6,319.7
Land and Development [Member]
Segment Reporting Information [Line Items]
Identifiable assets		49.1				89.8				49.1	89.8	460.6
Depreciation, depletion and amortization										0.7	0.7	1.4
Investment in unconsolidated entities		0				14.4				0	14.4	28.6
Land and Development [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										142.4	243.8	119.8
Segment income (loss)										22.5	13.8	4.6
Land and Development [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales										142.4	243.8	119.8
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets		59.5				173.6				59.5	173.6	52.3
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Identifiable assets		2,671.2				2,410.1				2,671.2	2,410.1	2,356.8
Depreciation, depletion and amortization										5.4	5.3	8.2
Capital expenditures										34.3	20.7	16.5
Investment in unconsolidated entities		$ 0.4				$ 0.4				0.4	0.4	(3.1)
Discontinued Operations
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization										0	0	57.2
Capital expenditures										$ 0	$ 0	$ 45.2

Segment Information - Changes i

Segment Information - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Goodwill [Roll Forward]
Goodwill, beginning of fiscal year	$ 5,528.3	$ 4,778.1
Goodwill, end of fiscal year	5,577.6	5,528.3	$ 4,778.1
Corrugated Packaging [Member]
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year	1,865.7	1,722.5	1,667.5
Accumulated impairment losses, beginning of period	0	0	0
Goodwill, beginning of fiscal year	1,865.7	1,722.5	1,667.5
Goodwill acquired	65.4	137.6	52.4
Goodwill disposed of	(4.2)	0	(24)
Purchase price allocation adjustments	2.3	(1.2)	(4.9)
Translation adjustments	(38.3)	6.8	31.5
Goodwill, Gross end of fiscal year	1,890.9	1,865.7	1,722.5
Accumulated impairment losses, end of period	0	0	0
Goodwill, end of fiscal year	1,890.9	1,865.7	1,722.5
Consumer Packaging [Member]
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year	3,705.4	3,098.4	3,022.4
Accumulated impairment losses, beginning of period	(42.8)	(42.8)	(42.8)
Goodwill, beginning of fiscal year	3,662.6	3,055.6	2,979.6
Goodwill acquired	23.8	907.8	8
Goodwill disposed of	0	(329.6)	0
Purchase price allocation adjustments	18.4	9.3	67.6
Translation adjustments	(18.1)	19.5	0.4
Goodwill, Gross end of fiscal year	3,729.5	3,705.4	3,098.4
Accumulated impairment losses, end of period	(42.8)	(42.8)	(42.8)
Goodwill, end of fiscal year	3,686.7	3,662.6	3,055.6
Operating Segments [Member]
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year	5,571.1	4,820.9	4,689.9
Accumulated impairment losses, beginning of period	(42.8)	(42.8)	(42.8)
Goodwill, beginning of fiscal year	5,528.3	4,778.1	4,647.1
Goodwill acquired	89.2	1,045.4	60.4
Goodwill disposed of	(4.2)	(329.6)	(24)
Purchase price allocation adjustments	20.7	8.1	62.7
Translation adjustments	(56.4)	26.3	31.9
Goodwill, Gross end of fiscal year	5,620.4	5,571.1	4,820.9
Accumulated impairment losses, end of period	(42.8)	(42.8)	(42.8)
Goodwill, end of fiscal year	$ 5,577.6	$ 5,528.3	$ 4,778.1

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	May 15, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Common Stock, Par or Stated Value Per Share				$ 0.01	$ 0.01
Depreciation				$ 923.8	$ 855.9	$ 848.9
Finite-Lived Intangible Assets, Amortization Expense				300.8	$ 234	212.4
Secured Debt [Member] | Capital Lease Obligations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Long-term Debt				$ 171
Specialty Chemicals Business [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Outstanding common stock percentage distributed	100.00%
Common Stock, Par or Stated Value Per Share	$ 0.01
Borrowing in Contemplation of Separation of Business	$ 500
Trust Funded By Company and Assumed by Ingevity to Secure the Principal Payment of Capital Lease Upon Maturity	68.9
Long-Term Asset for the Estimated Fair Value of Principal and Interest Payments on Capital Lease Obligation Assumed By Ingevity	108.2
Costs Associated with the Closure of Brazil Facility and Other Severance and Stock-Based Compensation Expenses						10
Goodwill, Impairment Loss			$ 478.3
Depreciation						30.4
Finite-Lived Intangible Assets, Amortization Expense						$ 26.8
Specialty Chemicals Business [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Customer Lists [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)		$ 101.1
Specialty Chemicals Business [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Secured Debt [Member] | Capital Lease Obligations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Long-term Debt	$ 80
Debt Instrument, Interest Rate, Effective Percentage	7.67%

Discontinued Operations - Disco

Discontinued Operations - Discontinued Operations (Income Statement Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income tax benefit	$ 0	$ 0	$ 32.3
Loss from discontinued operations			(544.7)
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Specialty Chemicals Business [Member]
Net sales			533.7
Cost of goods sold			387.5
Selling, general and administrative, excluding intangible amortization			65.6
Selling, general and administrative intangible amortization			28.8
Restructuring and other costs			49.5
Impairment of Specialty Chemicals goodwill and intangibles			579.4
Operating loss			(577.1)
Interest income (expense) and other income (expense), net			0.1
Loss from discontinued operations before income taxes			(577)
Income tax benefit			32.3
Loss from discontinued operations			$ (544.7)

Discontinued Operations - Dis_2

Discontinued Operations - Discontinued Operations Discontinued Operations (Depreciation, Amortization and Capital Expenditures) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2016USD ($)
Impairment of Specialty Chemicals goodwill and intangibles	$ 579.4
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Specialty Chemicals Business [Member]
Depreciation, depletion and amortization	57.2
Impairment of Specialty Chemicals goodwill and intangibles	579.4
Capital expenditures	$ (45.2)

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Inventories [Abstract]
Finished goods and work in process	$ 867	$ 905
Raw materials	730	614.2
Supplies and spare parts	368.2	360.7
Inventories at FIFO cost	1,965.2	1,879.9
LIFO reserve	(135.6)	(82.6)
Net inventories	$ 1,829.6	$ 1,797.3

Assets Held For Sale - Addition

Assets Held For Sale - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale	$ 59.5	$ 173.6
Land and Development Portfolio Assets [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale	$ 33.5	$ 150.4

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 14,419.9	$ 13,682.5
Less: accumulated depreciation, depletion and amortization	(5,337.4)	(4,564.2)
Property, plant and equipment, net	9,082.5	9,118.3
Land and Buildings [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	2,078.9	2,034.3
Machinery and Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	12,064	11,349.7
Forestlands and Mineral Rights [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	158	208.3
Transportation Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	30.1	30.7
Leasehold Improvements [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 88.9	$ 59.5

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Depreciation	$ 923.8	$ 855.9	$ 848.9

Other Intangible Assets - Sched

Other Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	16 years 7 months 6 days
Gross Carrying Amount	$ 4,318.3	$ 4,227
Accumulated Amortization	$ (1,196.3)	(897.7)
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	16 years 8 months 12 days
Gross Carrying Amount	$ 4,123.7	4,046.2
Accumulated Amortization	$ (1,079.8)	(806)
Favorable Contracts [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	10 years 1 month 6 days
Gross Carrying Amount	$ 47.8	48.2
Accumulated Amortization	$ (34.8)	(30.7)
Technology and Patents [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	10 years 8 months 12 days
Gross Carrying Amount	$ 41.2	31.8
Accumulated Amortization	$ (18)	(14.4)
Trademarks and Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	19 years 9 months 18 days
Gross Carrying Amount	$ 77.6	74.7
Accumulated Amortization	$ (43.9)	(31.4)
Noncompete Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	2 years
Gross Carrying Amount	$ 3.4	2.5
Accumulated Amortization	$ (1.7)	(0.6)
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	9 years 7 months 6 days
Gross Carrying Amount	$ 24.6	23.6
Accumulated Amortization	$ (18.1)	$ (14.6)

Other Intangible Assets - Estim

Other Intangible Assets - Estimated Intangible Asset Future Amortization Expense (Details) $ in Millions	Sep. 30, 2018USD ($)
Other Intangible Assets [Abstract]
Fiscal 2,019	$ 300.1
Fiscal 2,020	289.6
Fiscal 2,021	243.8
Fiscal 2,022	234.6
Fiscal 2,023	$ 226.4

Other Intangible Assets - Addit

Other Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Other Intangible Assets [Abstract]
Intangible Assets Amortization Expense	$ 300.8	$ 234	$ 212.4
Other Intangible Assets Amortization Expense	$ 27.6	$ 22.2	$ 23.4

Fair Value - Additional Informa

Fair Value - Additional Information (Details) - USD ($) $ in Millions	Sep. 25, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 29, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Maximum eligible receivables that may be sold	$ 550								$ 490
Non-cash transaction to repurchase receivables previously sold to financial institution	$ 424.8
Estimated loss on sale of accounts receivable in a fiscal year							$ 11
Land and Development impairments		$ 2.6	$ 1.7	$ 27.6	$ 4	$ 42.7	$ 31.9	$ 46.7
Consumer Packaging [Member] | Customer Relationships [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Impairment of Intangible Assets, Finite-lived								$ 17.6

Fair Value - Summary of Activit

Fair Value - Summary of Activity Under A/R Sales Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Receivable from financial institution at beginning of fiscal year	$ 24.9	$ 13.8
Receivables sold to the financial institution and derecognized	1,664	1,542.5
Receivables collected by financial institution	(1,573.8)	(1,466.7)
Cash proceeds from financial institution	(115.1)	(64.7)
Receivable from financial institution at September 30,	$ 0	$ 24.9

Debt - Schedule of Carrying Val

Debt - Schedule of Carrying Value and Weighted Average Interest Rate of Individual Components of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Total debt	$ 6,415.2	$ 6,554.8
Less: current portion of debt	740.7	608.7
Long-term debt due after one year	$ 5,674.5	$ 5,946.1
Debt, Weighted Average Interest Rate	4.10%	3.60%
Notes Due Fiscal 2019 to 2022 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 1,470.9	$ 1,484.5
Debt, Weighted Average Interest Rate	4.20%	4.20%
Notes Due Fiscal 2023 to 2028 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 2,534.4	$ 1,368.8
Debt, Weighted Average Interest Rate	3.80%	3.60%
Notes Due Fiscal 2030 to 2033 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 964.1	$ 975.5
Debt, Weighted Average Interest Rate	5.20%	5.20%
Notes Due Fiscal 2037 to 2047 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 178.5	$ 178.8
Debt, Weighted Average Interest Rate	6.30%	6.30%
Term Loan Facilities [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 599.4	$ 1,622.7
Debt, Weighted Average Interest Rate	3.70%	2.50%
Revolving Credit and Swing Facilities [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 355	$ 436.4
Debt, Weighted Average Interest Rate	3.20%	1.10%
Receivables Facility [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Total debt		$ 110
Debt, Weighted Average Interest Rate		2.10%
Capital Lease Obligations [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 171	$ 177
Debt, Weighted Average Interest Rate	4.10%	4.30%
Supplier Financing and Commercial Card Programs [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 105.1	$ 130.3
International and Other Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 36.8	$ 70.8
Debt, Weighted Average Interest Rate	6.10%	6.80%

Debt - Additional Information (

Debt - Additional Information (Details)

Apr. 27, 2018EUR (€)

Mar. 14, 2018USD ($)

Mar. 07, 2018USD ($)

Mar. 06, 2018USD ($)

Oct. 31, 2017USD ($)

Aug. 24, 2017USD ($)

Jun. 30, 2017USD ($)

May 15, 2017USD ($)

Feb. 10, 2017USD ($)

Jul. 22, 2016USD ($)

Jun. 22, 2016USD ($)

Jul. 01, 2015USD ($)

Mar. 31, 2018USD ($)

Oct. 31, 2017USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)

Sep. 30, 2016USD ($)

Mar. 02, 2017EUR (€)

Mar. 24, 2016USD ($)

Debt Instrument [Line Items]

Unamortized fair market value step-up

$ 250,800,000

Unamortized fair market value step-up, weighted average remaining life

12 years 3 months 18 days

Weighted average interest rate excluding fair value step-up

4.60%

Letters of credit outstanding, amount

$ 104,900,000

Fair value of debt

6,400,000,000

$ 6,800,000,000

Amortization of debt issuance costs

6,300,000

4,500,000

$ 4,600,000

Repayment of debt

$ 2,032,900,000

$ 2,331,900,000

$ 1,073,300,000

Debt, Weighted Average Interest Rate

4.10%

3.60%

DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 3,800,000,000

Debt issuance costs

$ 4,000,000

Debt instrument, interest rate description

The applicable interest rate margin will be 1.125% to 2.000% per annum for LIBOR rate loans and 0.125% to 1.000% per annum for alternate base rate loans, in each case depending on the Leverage Ratio (as defined in the credit agreement) or Holdco’s corporate credit ratings, whichever yields a lower applicable interest rate margin, at such time. In addition, we will be required to pay a commitment fee of 0.125% per annum to 0.300% per annum (depending on the Leverage Ratio or the Company’s corporate credit ratings, whichever yields a lower fee) on the unused term loan commitments, accruing from June 5, 2018 until the earlier of the funding of the loans under the Delayed Draw Credit Facilities or the Delayed Draw Termination Date.

Foreign Exchange Contract [Member]

Debt Instrument [Line Items]

Derivative, Notional Amount

356,000,000

$ 47,800,000

Minimum [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Line of credit facility, commitment fee percentage

0.125%

Minimum [Member] | LIBOR [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

1.125%

Minimum [Member] | Base Rate [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

0.125%

Maximum [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Line of credit facility, commitment fee percentage

0.30%

Maximum [Member] | LIBOR [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

2.00%

Maximum [Member] | Base Rate [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

1.00%

Revolver, Receivables Facility and Term Loan [Member]

Debt Instrument [Line Items]

Line of credit facility, remaining borrowing capacity

3,200,000,000

Public Bond Obligations [Member]

Debt Instrument [Line Items]

Debt instrument, face amount

$ 4,900,000,000

$ 3,800,000,000

Senior Notes due 2025 [Member]

Debt Instrument [Line Items]

Debt instrument, face amount

$ 600,000,000

Debt instrument, interest rate

3.75%

Debt instrument, maturity year

2,025

Debt instrument, discount

$ 1,700,000

Debt instrument, issuance costs

$ 4,900,000

Debt Instrument, Interest Rate, Effective Percentage

3.93%

Senior Notes due 2028 [Member]

Debt Instrument [Line Items]

Debt instrument, face amount

$ 600,000,000

Debt instrument, interest rate

4.00%

Debt instrument, maturity year

2,028

Debt instrument, discount

$ 1,000,000

Debt instrument, issuance costs

$ 5,000,000

Debt Instrument, Interest Rate, Effective Percentage

4.12%

Term Loan Facilities [Member]

Debt Instrument [Line Items]

Repayment of debt

$ 540,000,000

Term Loan Facilities [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Debt, Weighted Average Interest Rate

3.70%

2.50%

Commercial Paper [Member]

Debt Instrument [Line Items]

Repayment of debt

445,000,000

Commercial Paper [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 2,000,000,000

Borrowings outstanding

0

Aggregate Principal Amount of Short-term Unsecured Commercial Paper Program, Maximum

$ 1,000,000,000

$ 1,000,000,000

Commercial Paper [Member] | Unsecured Debt [Member] | Minimum [Member]

Debt Instrument [Line Items]

Debt Instrument, notice period for termination

30 days

Commercial Paper [Member] | Unsecured Debt [Member] | Maximum [Member]

Debt Instrument [Line Items]

Debt instrument, maturity period

397 days

Receivables Facility [Member]

Debt Instrument [Line Items]

Repayment of debt

100,000,000

Receivables Facility [Member] | Secured Debt [Member]

Debt Instrument [Line Items]

Debt instrument, maximum borrowing capacity, amount

571,000,000

$ 577,600,000

Long-term Debt

$ 0

$ 110,000,000

Credit facility maturity date

Jul. 22, 2019

Debt, Weighted Average Interest Rate

2.10%

Receivables backed financing, maximum borrowing amount

$ 700,000,000

Restriction on Exclusion of Eligible Receivables of Specific Obligors, Aggregate Maximum Percentage

7.50%

Restriction on Exclusion of Eligible Receivables of Specific Obligors, Obligor Maximum Percentage of Aggregate Balance

2.50%

Asset Securitization Facility Commitment Fee Percentage

0.25%

0.25%

Loans and Leases Receivable, Collateral for Secured Borrowings

$ 887,000,000

Receivables Facility [Member] | Secured Debt [Member] | LIBOR [Member]

Debt Instrument [Line Items]

Applicable margin

0.85%

Variable rate basis

one month LIBOR

Receivables Facility [Member] | Secured Debt [Member]

Debt Instrument [Line Items]

Prepayment of amortization payments

$ 415,000,000

Sumitomo Mitsui Banking Corporation Unsecured Credit Facility [Member]

Debt Instrument [Line Items]

Repayment of debt

$ 104,700,000

Sumitomo Mitsui Banking Corporation Unsecured Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 200,000,000

Credit facility maturity date

Feb. 7, 2018

Current portion of debt

0

$ 106,700,000

Senior Notes Due September 15, 2024 | Unsecured Debt [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.00%

Debt instrument, discount

$ 1,400,000

Debt Instrument, Interest Rate, Effective Percentage

3.18%

Long-term Debt

$ 500,000,000

Deferred finance costs, current, gross

$ 4,200,000

Senior Notes Due September 15, 2027 [member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.375%

Debt instrument, discount

$ 200,000

Debt Instrument, Interest Rate, Effective Percentage

3.48%

Long-term Debt

$ 500,000,000

Deferred finance costs, current, gross

4,300,000

Term Loan Facility [Member]

Debt Instrument [Line Items]

Prepayment of outstanding principle amount

$ 540,000,000

485,000,000

Term Loan Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term Debt

1,023,500,000

Prepayment of amortization payments

$ 575,000,000

$ 200,000,000

Debt Instrument, Term, in Years

5 years

Credit Facility, maximum borrowing capacity

$ 2,300,000,000

Amount Drawn on Unsecured Term Loan

1,200,000,000

Amount Which Can Be Drawn On A Delayed Draw Basis Not Later Than Nine Months After the Closing of the Credit Agreement

$ 1,100,000,000

Amount Drawn On Delayed Draw Term Loan

$ 600,000,000

Revolving Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term Debt

0

0

Debt Instrument, Term, in Years

5 years

Credit Facility, maximum borrowing capacity

$ 2,000,000,000

Committed Principal Amount Extended to July 1, 2022

$ 1,900,000,000

Credit facility maturity date

Jul. 1, 2020

Revolving Credit Facility [Member] | Unsecured Debt [Member] | Letter of Credit [Member]

Debt Instrument [Line Items]

Capacity available for special purpose

150,000,000

Revolving Credit Facility [Member] | Unsecured Debt [Member] | Canadian Dollar Borrowing [Member]

Debt Instrument [Line Items]

Capacity available for special purpose

400,000,000

Revolving Credit Facility [Member] | Unsecured Debt [Member] | Future Mexican Peso Sub-Facility [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 200,000,000

Credit Facility [Member] | Unsecured Debt [Member] | Minimum [Member]

Debt Instrument [Line Items]

Facility commitment

0.125%

Credit Facility [Member] | Unsecured Debt [Member] | Maximum [Member]

Debt Instrument [Line Items]

Facility commitment

0.25%

Credit Facility [Member] | Unsecured Debt [Member] | LIBOR Based Borrowings [Member]

Debt Instrument [Line Items]

Applicable margin

1.125%

Credit Facility [Member] | Unsecured Debt [Member] | LIBOR Based Borrowings [Member] | Minimum [Member]

Debt Instrument [Line Items]

Applicable margin

1.00%

Credit Facility [Member] | Unsecured Debt [Member] | LIBOR Based Borrowings [Member] | Maximum [Member]

Debt Instrument [Line Items]

Applicable margin

1.50%

Credit Facility [Member] | Unsecured Debt [Member] | Base Rate [Member]

Debt Instrument [Line Items]

Applicable margin

0.125%

Credit Facility [Member] | Unsecured Debt [Member] | Base Rate [Member] | Minimum [Member]

Debt Instrument [Line Items]

Applicable margin

0.00%

Credit Facility [Member] | Unsecured Debt [Member] | Base Rate [Member] | Maximum [Member]

Debt Instrument [Line Items]

Applicable margin

0.50%

Farm Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term Debt

599,400,000

599,200,000

Debt Instrument, Term, in Years

7 years

Credit Facility, maximum borrowing capacity

$ 600,000,000

Cooperatieve Rabobank U.A., New York Branch European Revolving Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 600,000,000

Credit facility maturity date

May 14, 2018

Line of credit facility, maximum Euro denominated borrowing capacity

$ 600,000,000

Current portion of debt

211,600,000

Cooperatieve Rabobank U.A., New York Branch European Revolving Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term Debt

355,000,000

Credit Facility, maximum borrowing capacity | €

€ 500,000,000

Credit facility maturity date

Apr. 27, 2021

Line of credit facility, maximum Euro denominated borrowing capacity | €

€ 500,000,000

Cooperatieve Rabobank U.A., New York Branch European Revolving Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Incremental line of credit | €

€ 100,000,000

Debt instrument, maturity period

3 years

Cooperatieve Rabobank U.A., New York Branch European Revolving Credit Facility [Member] | Unsecured Debt [Member] | Foreign Exchange Contract [Member]

Debt Instrument [Line Items]

Derivative, Notional Amount

$ 356,000,000

Wells Fargo Bank, NA Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 450,000,000

$ 450,000,000

Debt instrument, maturity period

364 days

Debt, Weighted Average Interest Rate

3.39%

Borrowings outstanding

$ 0

Debt instrument, maturity date

Oct. 28, 2019

Cooperatieve Rabobank U.A., New York Branch Other Revolving Credit Facility [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity | €

€ 100,000,000

Current portion of debt

$ 0

$ 118,100,000

364-Day Term Loan [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 300,000,000

Debt instrument, maturity period

364 days

Three Year Term Loan [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 1,750,000,000

Debt instrument, maturity period

3 years

Five Year Term Loan | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 1,750,000,000

Debt instrument, maturity period

5 years

Debt - Schedule of Aggregate Ma

Debt - Schedule of Aggregate Maturities of Debt (Details) $ in Millions	Sep. 30, 2018USD ($)
Long-term Debt, Excluding Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Fiscal 2,019	$ 726.6
Fiscal 2,020	474.5
Fiscal 2,021	350.3
Fiscal 2,022	1,000.9
Fiscal 2,023	350.1
Thereafter	3,136.6
Fair value of debt step-up, deferred financing costs and unamortized bond discounts	205.2
Total	6,244.2
Capital Lease Obligations [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Fiscal 2,019	5
Fiscal 2,020	4.2
Fiscal 2,021	2.5
Fiscal 2,022	2.1
Fiscal 2,023	0.6
Thereafter	138.1
Fair value step-up	18.5
Total	$ 171

Operating Leases - Schedule of

Operating Leases - Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases (Details) $ in Millions	Sep. 30, 2018USD ($)
Leases [Abstract]
Fiscal 2,019	$ 132.1
Fiscal 2,020	112
Fiscal 2,021	87.9
Fiscal 2,022	66.8
Fiscal 2,023	51.6
Thereafter	165.4
Total future minimum lease payments	$ 615.8

Operating Leases - Additional I

Operating Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Leases [Abstract]
Rental expense	$ 243.7	$ 210.5	$ 199.3

Special Purpose Entities (Detai

Special Purpose Entities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Dec. 06, 2013	Dec. 31, 2007
Debt Instrument [Line Items]
Restricted assets held by special purpose entities	$ 1,281	$ 1,287.4
Non-recourse liabilities held by special purpose entities	$ 1,153.7	$ 1,161.9
Installment Note [Member]
Debt Instrument [Line Items]
Notes Receivable Interest Rate	5.207%
MeadWestvaco [Member] | Timber Note [Member]
Debt Instrument [Line Items]
Restricted assets held by special purpose entities	$ 366			$ 398
MeadWestvaco [Member] | Secured Financing Liability, Maturity in October 2027 [Member]
Debt Instrument [Line Items]
Non-recourse liabilities held by special purpose entities	323.1			$ 338.3
MeadWestvaco [Member] | Installment Note [Member]
Debt Instrument [Line Items]
Restricted assets held by special purpose entities	915		$ 860
MeadWestvaco [Member] | Secured Financing Liability, Maturity in December 2023 [Member]
Debt Instrument [Line Items]
Non-recourse liabilities held by special purpose entities	$ 830.6		$ 774

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Net sales to affiliated companies	$ 418.8	$ 423.6	$ 346.6
Accounts receivable due from affiliated companies	$ 64.2	$ 65.1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Sep. 30, 2018USD ($)lawsuit
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 10.8
Number of Lawsuits the Company Has Been Named a Defendant in Asbestos-related Personal Injury Litigation | lawsuit	735
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 50
Guarantor Obligations, Current Carrying Value	11.7
Other Long Term Liabilities [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	6.7
Other Current Liabilities [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	4.1
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment, Estimated Amount	$ 203

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	$ (457.3)		$ (626.4)
Other comprehensive income (loss) before reclassifications	[1]	(252.2)		104.3
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	14.2		35.1
Sale of HH&B	[1]			29.7
Net current period other comprehensive (loss) income		(238)	[1]	169.1	[1]	$ 145.9
Balance at end of period	[1]	(695.3)		(457.3)		(626.4)
Accumulated Net Gain (Loss) from Designated or Quality Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	(0.7)		(0.2)
Other comprehensive income (loss) before reclassifications	[1]	0		0
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	0.5		(0.5)
Sale of HH&B	[1]			0
Net current period other comprehensive (loss) income	[1]	0.5		(0.5)
Balance at end of period	[1]	(0.2)		(0.7)		(0.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	(462.5)		(523.8)
Other comprehensive income (loss) before reclassifications	[1]	(18.6)		22.8
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	15.2		35.6
Sale of HH&B	[1]			2.9
Net current period other comprehensive (loss) income	[1]	(3.4)		61.3
Balance at end of period	[1]	(465.9)		(462.5)		(523.8)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	5.2		(102.4)
Other comprehensive income (loss) before reclassifications	[1]	(234.4)		80.8
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	0		0
Sale of HH&B	[1]			26.8
Net current period other comprehensive (loss) income	[1]	(234.4)		107.6
Balance at end of period	[1]	(229.2)		5.2		(102.4)
Accumulated Net Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	0.7		0
Other comprehensive income (loss) before reclassifications	[1]	0.8		0.7
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	(1.5)		0
Sale of HH&B	[1]			0
Net current period other comprehensive (loss) income	[1]	(0.7)		0.7
Balance at end of period	[1]	$ 0		$ 0.7		$ 0
[1]	All amounts are net of tax and noncontrolling interest

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss) - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount		$ 20.9	$ 56.4	$ 379.7	[1]
Amortization of net actuarial loss, Tax		(5.9)	(20.4)	(143.2)	[1]
Amortization and settlement recognition of net actuarial loss, included in pension cost		15	36	236.5	[1]
Amortization of prior service credits (costs), Pre-Tax Amount		0.3	(0.4)	1.8
Amortization of prior service credits (costs), Tax		(0.1)	0.2	(0.7)
Amortization of prior service credits (costs), Net of Tax		0.2	(0.2)	1.1
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, before Tax			4.2
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Tax			1.3
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Net of Tax		0	2.9	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, before Tax			26.8
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, Tax			0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, Net of Tax		0	26.8	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax		0.7	(0.8)	1.9
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		(0.2)	0.3	(0.7)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		0.5	(0.5)	1.2
Available for sale security, before Tax		(1.5)
Available for sale security, Tax		0
Available for sale security, Net of Tax		(1.5)	0	$ 0
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount	[2]	20.9	(56.3)
Amortization of net actuarial loss, Tax	[2]	(5.9)	20.4
Amortization and settlement recognition of net actuarial loss, included in pension cost	[2]	15	(35.9)
Amortization of prior service credits (costs), Pre-Tax Amount	[2],[3]	0.3	0.5
Amortization of prior service credits (costs), Tax	[2],[3]	(0.1)	(0.2)
Amortization of prior service credits (costs), Net of Tax	[2],[3]	0.2	0.3
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, before Tax	[2],[4]		(4.2)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Tax	[2],[4]		1.3
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Net of Tax	[2],[4]		(2.9)
Defined Benefit Plans, before Tax	[2]	21.2	(60)
Defined Benefit Plans, Tax	[2]	(6)	21.5
Defined Benefit Plans, Net of Tax	[2]	15.2	(38.5)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, before Tax	[2],[4]		(26.8)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, Tax	[2],[4]		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, Net of Tax	[2],[4]		(26.8)
Available for sale security, before Tax	[2]	(1.5)
Available for sale security, Tax	[2]	0
Available for sale security, Net of Tax	[2]	(1.5)
Total Reclassifications From Other Comprehensive Income Before Tax	[2]	20.4	(86)
Total Reclassifications From Other Comprehensive Income Tax Portion	[2]	(6.2)	21.2
Total Reclassifications From Other Comprehensive Income Net of Tax	[2]	14.2	(64.8)
Parent [Member] | Foreign Exchange Contract [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	[2],[5]	0.7	0.8
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[5]	(0.2)	(0.3)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[5]	$ 0.5	$ 0.5
[1]	Includes pension risk transfer expense.
[2]	Amounts in parentheses indicate charges to earnings. Amounts pertaining to noncontrolling interests are excluded.
[3]	All amounts are net of tax and noncontrolling interest
[4]	Included in gain on sale of HH&B.
[5]	These accumulated other comprehensive income components are included in net sales.

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Loss and Other Comprehensive Income (Loss) - Schedule of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2016
Other Comprehensive Income Loss [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation (Loss) Gain, before Tax	$ (234.4)		$ 80.7		$ 109.8
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, before Tax			26.8
Net deferred loss on cash flow hedges, Pre-Tax Amount					(0.7)
Reclassification adjustment of net (gain) loss on cash flow hedges included in earnings, Pre-Tax Amount	0.7		(0.8)		1.9
Net actuarial gain (loss) arising during period, Pre-Tax Amount	(29)		34.1		(354)
Amortization of net actuarial loss, Pre-Tax Amount	20.9		56.4		379.7	[1]
Prior service cost arising during the period, Pre-Tax Amount	(7.8)		1		2.3
Amortization of prior service credits (costs), Pre-Tax Amount	0.3		(0.4)		1.8
Unrealized gain on available for sale security, before tax	0.8		0.7
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, before Tax			4.2
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax					20.2
Reclassification adjustment of net gain on available for sale security included in earnings, Pre-Tax	(1.5)
Consolidated other comprehensive loss	(250)		202.7		161
Less: Other comprehensive income attributable to noncontrolling interests	0		(0.2)		0.7
Other comprehensive loss attributable to common stockholders	(250)		202.5		161.7
Foreign currency translation (loss) gain, Tax	0		0		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale of HH&B, Tax			0
Net deferred loss on cash flow hedges, Tax					0.3
Reclassification adjustment of net loss on cash flow hedges included in earnings, Tax	(0.2)		0.3		(0.7)
Net actuarial gain (loss) arising during period, Tax	15.9		(11.9)		129.4
Amortization of net actuarial loss, Tax	(5.9)		(20.4)		(143.2)	[1]
Other Comprehensive Income (Loss), Pension and Other Postretirement Plans, Net Prior Service Credit Arising During Period, Tax	2.3		(0.3)		(0.9)
Amortization of prior service cost (credit), Tax	(0.1)		0.2		(0.7)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	0		0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Tax			(1.3)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax					0
Reclassification adjustment of net gain on available for sale security included in earnings, Tax	0
Consolidated other comprehensive loss	12		(33.4)		(15.8)
Less: Other comprehensive income (loss) attributable to noncontrolling interests, Tax	0		0		0
Other comprehensive loss attributable to common stockholders	12		(33.4)		(15.8)
Foreign currency translation (loss) gain, Net of Tax Amount	(234.4)		80.7		109.8
Sale of HH&B	0		26.8		0
Deferred loss on cash flow hedges	0		0		(0.4)
Reclassification adjustment of net loss on cash flow hedges included in earnings, Net of Tax Amount	0.5		(0.5)		1.2
Net actuarial (loss) gain arising during period	(13.1)		22.2		(224.6)
Amortization and settlement recognition of net actuarial loss, included in pension and postretirement cost	15		36		236.5	[1]
Prior service (cost) credit arising during period	(5.5)		0.7		1.4
Amortization and curtailment recognition of prior service (credit) cost, included in pension and postretirement cost	0.2		(0.2)		1.1
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	0.8		0.7
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Sale of HH&B, Net of Tax	0		2.9		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0		0		20.2
Reclassification adjustment of net gain on available for sale security included in earnings, Net of Tax	(1.5)		0		0
Other comprehensive (loss) income, net of tax	(238)		169.3		145.2
Less: Other comprehensive income attributable to noncontrolling interests			(0.2)		0.7
Net current period other comprehensive (loss) income	$ (238)	[2]	$ 169.1	[2]	$ 145.9
[1]	Includes pension risk transfer expense.
[2]	All amounts are net of tax and noncontrolling interest

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jul. 31, 2015
Equity [Abstract]
Stock repurchase program, number of shares authorized to be repurchased				40
Authorized share repurchase as a percentage of common stock outstanding				15.00%
Treasury stock, shares, acquired	3.4	1.8	8.1
Purchases of common stock	$ 195.1	$ 93	$ 335.3
Stock repurchase program, remaining number of shares authorized to be repurchased	21.3

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-based Compensation Plans (Details)	12 Months Ended
	Sep. 30, 2018shares	[1]
Amended and Restated 2016 Incentive Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available For Issuance	11,700,000
Shares Available For Future Grant	8,000,000
Shares To Be Issued If Performance Is Achieved At Maximum	2,500,000
Expect To Make New Awards	Yes
2004 Incentive Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available For Issuance	15,800,000	[2]
Shares Available For Future Grant	3,100,000	[2]
Shares To Be Issued If Performance Is Achieved At Maximum	0	[2]
Expect To Make New Awards	No	[2]
2005 Performance Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available For Issuance	12,800,000	[2]
Shares Available For Future Grant	9,000,000	[2]
Shares To Be Issued If Performance Is Achieved At Maximum	0	[2]
Expect To Make New Awards	No	[2]
RockTenn (SSCC) Equity Inventive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available For Issuance	7,900,000	[3]
Shares Available For Future Grant	5,900,000	[3]
Shares To Be Issued If Performance Is Achieved At Maximum	0	[3]
Expect To Make New Awards	No	[3]
[1]	As part of the Separation, equity-based incentive awards were generally adjusted to maintain the intrinsic value of awards immediately prior to the Separation. The number of unvested restricted stock awards and unexercised stock options and SARs at the time of the Separation were increased by an exchange factor of approximately 1.12. In addition, the exercise price of unexercised stock options and SARs at the time of the Separation was converted to decrease the exercise price by an exchange factor of approximately 1.12.
[2]	In connection with the Combination, WestRock assumed all RockTenn and MWV equity incentive plans. We issued awards to certain key employees and our directors pursuant to our RockTenn 2004 Incentive Stock Plan, as amended, and our MWV 2005 Performance Incentive Plan, as amended. The awards were converted into WestRock awards using the conversion factor as described in Business Combination Agreement.
[3]	In connection with the Smurfit-Stone Acquisition, we assumed the Smurfit-Stone equity incentive plan, which was renamed the Rock-Tenn Company (SSCC) Equity Incentive Plan. The awards were converted into shares of RockTenn Common Stock, options and restricted stock units, as applicable, using the conversion factor as described in the merger agreement.

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Share-based Compensation Plans (Parenthetical) (Details)	May 15, 2016
Stock Based Compensation [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Spin-off Adjustment, Conversion Factor	1.12

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 06, 2017	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 66.8	$ 60.9		$ 75.7
Share-based Compensation Expense Included in the Gain on Sale of HH&B			2.9
Reduction of Share-based Compensation Expense Related to the Rescission of Shares Granted in Excess of Plan Limits			5.4
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		19.4	22.5		29.2
Proceeds from Stock Options Exercised		$ 44.4	$ 59.2		33.9
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Stock options granted during period		0	0
Share-based Compensation Arrangement by Share-based Payment Award, Stock Appreciation Rights, Exercises in Period, Intrinsic Value		$ 0.5	$ 0.4		$ 0.2
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Share-based Compensation Arrangement by Share-based Payment Award, Contractual Term, Maximum		10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 8.06
Aggregate intrinsic value of options exercised		$ 67.4	$ 54.3		$ 14.5
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized		$ 0.4
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition		3 months 18 days
MPS [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ratio of MPS Shares to WestRock Shares	33.00%
Weighted Average Grant Date Fair Value, Granted	$ 54.24
Fair value of share-based awards issued in business combinations	$ 1.9
MPS [Member] | Restricted Stock with Service Condition Assumed in Purchase Accounting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	119,373		119,373	[1]
[1]	These shares vest over approximately one to three years.

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Details) - Stock Options [Member]	12 Months Ended
	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term in years	7 years
Expected volatility	38.30%
Risk-free interest rate	1.60%
Dividend yield	4.50%

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Changes in Stock Options (Details) - Stock Options [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding | shares	5,866,127
Exercised | shares	(1,582,313)
Expired | shares	(5,819)
Forfeited | shares	(24,341)
Outstanding | shares	4,253,654
Exercisable at September 30, 2018 | shares	3,845,523
Vested and expected to vest at September 30, 2018 | shares	4,251,748
Weighted Average Exercise Price, Outstanding | $ / shares	$ 30.51
Weighted Average Exercise Price, Exercised | $ / shares	21.73
Weighted Average Exercise Price, Expired | $ / shares	37.17
Weighted Average Exercise Price, Forfeited | $ / shares	32.13
Weighted Average Exercise Price, outstanding, end of period | $ / shares	33.75
Weighted Average Exercise Price, exercisable at end of period | $ / shares	34.17
Stock Options, Vested and expected to vest at September 30, 2018 | $ / shares	$ 33.75
Weighted Average Remaining Contractual Term (in years), Outstanding	4 years 3 months 18 days
Weighted Average Remaining Contractual Term (in years), Exercisable at September 30, 2018	4 years
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest at September 30, 2018	4 years 3 months 18 days
Aggregate Intrinsic Value, Outstanding | $	$ 85.8
Aggregate Intrinsic Value, Exercisable at September 30, 2018 | $	76.1
Aggregate Intrinsic Value,, Vested and expected to vest at September 30, 2018 | $	$ 85.7

Share-Based Compensation - Su_4

Share-Based Compensation - Summary of Changes in SARs (Details) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding | shares	51,016
Exercised | shares	(9,935)
Expired | shares	(4,095)
Outstanding | shares	36,986
Exercisable at September 30, 2018 | shares	36,986
Weighted Average Exercise Price, Outstanding | $ / shares	$ 25.30
Weighted Average Exercise Price, Exercised | $ / shares	16.66
Weighted Average Exercise Price, Expired | $ / shares	27.69
Weighted Average Exercise Price, outstanding, end of period | $ / shares	27.36
Weighted Average Exercise Price, Vested and expected to vest at September 30, 2018 | $ / shares	$ 27.36
Weighted Average Remaining Contractual Term (in years), Outstanding	2 years 4 months 24 days
Weighted Average Remaining Contractual Term (in years), Exercisable at September 30, 2018	2 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding | $	$ 1
Aggregate Intrinsic Value, Exercisable at September 30, 2018 | $	$ 1

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Restricted Stock, Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year
Restricted Stock, Target Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Percentage of Award Based on Level of Performance Attained, Maximum	200.00%	200.00%
Percentage of Award Based on Level of Performance Attained, Minimum	0.00%	0.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 83.5	$ 83.5
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition		1 year 3 months 18 days
Restricted Stock, Total Shareholder Return Grant, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		2 years 10 months 24 days	2 years 10 months 24 days
Expected volatility		29.70%	30.60%
Risk-free rate		2.30%	1.40%
Stock Options [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 66.28	$ 64.41
Restricted Stock, Target Awards, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved		103.70%
Restricted Stock, Target Awards, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved			176.60%

Share-Based Compensation - Su_5

Share-Based Compensation - Summary of Changes in Unvested Restricted Stock (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units, Unvested	2,959,449
Shares/Units, Granted	1,116,111		1,605,113	1,750,546
Shares/Units, Vested	(697,717)		(1,112,909)	(1,589,761)
Shares/Units, Forfeited	(153,669)
Shares/Units, Unvested	3,224,174		2,959,449
Weighted Average Grant Date Fair Value, Unvested	$ 45.28
Weighted Average Grant Date Fair Value, Granted	69.36
Weighted Average Grant Date Fair Value, Vested	57.39
Weighted Average Grant Date Fair Value, Forfeited	45.07
Weighted Average Grant Date Fair Value, Unvested	$ 51.01	[1]	$ 45.28
[1]	Target awards granted with a performance condition, net of subsequent forfeitures, may be increased up to 200% of the target or decreased to zero, subject to the level of performance attained. The awards are reflected in the table at the target award amount of 100%. Based on current facts and assumptions we are forecasting the performance of the grants to be attained at levels that would result in the issuance of approximately 0.9 million additional shares. However, it is possible that the performance attained may vary.

Share-Based Compensation - Su_6

Share-Based Compensation - Summary of Changes in Unvested Restricted Stock (Parenthetical) (Details) - shares shares in Millions	Sep. 30, 2018	Sep. 30, 2018
Restricted Stock, Target Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Award Based on Level of Performance Attained, Maximum	200.00%	200.00%
Percentage of Award Based on Level of Performance Attained, Minimum	0.00%	0.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Performance Based Awards Reflected	100.00%
Additional Shares Expected to Be Issued Based on Current Projection of Performance Target Levels	0.9

Share-Based Compensation - Su_7

Share-Based Compensation - Summary of Restricted Stock Shares Granted (Details) - shares		Jun. 06, 2017	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2016
Restricted Stock, Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[1]		23,285	26,521		64,155
Restricted Stock, Attainment of Performance Condition in Excess of Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[2]		45,964	340,319		447,261
Restricted Stock Service Conditionand Cash Flowper Share Performance Conditionat Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[3],[4]		432,655	507,070		1,211,760
Restricted Stock, Service Condition and Relative Total Shareholder Return Market Condition at Target [Member] [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[4]		259,695	301,980
Restricted Stock with Service Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[5]		354,512	309,850		27,370
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			1,116,111	1,605,113		1,750,546
MPS [Member] | Restricted Stock with Service Condition Assumed in Purchase Accounting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		119,373		119,373	[6]
[1]	Non-employee director grants generally vest over a period of up to one year and are deemed issued on the grant date and have voting and dividend rights.
[2]	Shares granted in the table above include shares subsequently issued for the level of performance attained in excess of target. Shares issued in fiscal 2018 for the fiscal 2015 Cash Flow Per Share were at 103.7% of target. Shares issued in fiscal 2017 for the fiscal 2014 Cash Flow Per Share were at 176.6% of target. Shares issued in fiscal 2016 for the fiscal 2013 Cash Flow to Equity Ratio were at 200% of target. Shares issued in fiscal 2017 and 2016 also include shares accelerated for terminated employees primarily as a result of the Combination, which were achieved at between 146.5% and 200% of target.
[3]	Shares granted in fiscal 2015 were reduced by 50,326 shares at target related to the rescission of shares granted to our CEO that were inadvertently granted in excess of plan limits.
[4]	These employee grants vest over approximately three years and have adjustable ranges from 0 - 200% of target subject to the level of performance attained in the respective award agreement. The employee grants with a relative Total Shareholder Return condition were valued using a Monte Carlo simulation, the terms of which are outlined below.
[5]	These shares vest over approximately three to four years.
[6]	These shares vest over approximately one to three years.

Share-Based Compensation - Su_8

Share-Based Compensation - Summary of Restricted Stock Shares Granted (Parenthetical) (Details) - shares shares in Millions	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Number of Target Shares Related to Rescission of Shares Granted in Excess of Plan Limits		50,326
Restricted Stock, Target Awards, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved		103.70%
Restricted Stock, Target Awards, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved			176.60%
Restricted Stock, Target Awards, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved				200.00%
Restricted Stock, Target Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Percentage of Award Based on Level of Performance Attained, Maximum	200.00%	200.00%
Percentage of Award Based on Level of Performance Attained, Minimum	0.00%	0.00%
Minimum [Member] | Restricted Stock Accelerated in Connection with the Combination [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved			146.50%	146.50%
Minimum [Member] | Restricted Stock with Service Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Minimum [Member] | Restricted Stock with Service Condition Assumed in Purchase Accounting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year
Maximum [Member] | Restricted Stock Accelerated in Connection with the Combination [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved			200.00%	200.00%
Maximum [Member] | Restricted Stock with Service Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
Maximum [Member] | Restricted Stock with Service Condition Assumed in Purchase Accounting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years

Share-Based Compensation - Su_9

Share-Based Compensation - Summary of Restricted Stock Awards - Vested, Granted and Changes (Details) - Restricted Stock [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of restricted stock vested	697,717	1,112,909	1,589,761
Aggregate fair value of restricted stock vested	$ 46.1	$ 59.5	$ 57.5

Share-Based Compensation - Empl

Share-Based Compensation - Employee Stock Purchase Plan - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Feb. 02, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 66.8	$ 58	$ 75.7
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	15.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans	0.2	0.2	0.1
Share-based compensation expense	$ 1.6	$ 1.3	$ 0.4
Shares Available For Future Grant	2.4			2.5

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Income from continuing operations										$ 1,909.3	$ 698.6	$ 154.8
Less: Net (income) loss from continuing operations attributable to noncontrolling interest										(3.2)	9.6	(2.1)
Income available to common stockholders, before discontinued operations										1,906.1	708.2	152.7
Less: Distributed and undistributed income available to participating securities										(0.2)	(0.1)
Distributed and undistributed income attributable to common stockholders, before discontinued operations										1,905.9	708.1	152.7
Loss from discontinued operations (1)	[1]											(549)
Net income (loss) attributable to common stockholders										$ 1,905.9	$ 708.1	$ (396.3)
Denominator:
Basic weighted average shares outstanding										255.5	252.2	254
Effect of dilutive stock options and non-participating securities										4.3	3.5	3.9
Diluted weighted average shares outstanding										259.8	255.7	257.9
Basic earnings per share from continuing operations										$ 7.46	$ 2.81	$ 0.60
Basic loss per share from discontinued operations												(2.16)
Basic earnings (loss) per share attributable to common stockholders		$ 1.10	$ 1.05	$ 0.87	$ 4.45	$ 0.77	$ 1.30	$ 0.41	$ 0.32	7.46	2.81	(1.56)
Diluted earnings per share from continuing operations										7.34	2.77	0.59
Diluted loss per share from discontinued operations												(2.13)
Diluted earnings (loss) per share attributable to common stockholders		$ 1.08	$ 1.03	$ 0.86	$ 4.38	$ 0.76	$ 1.29	$ 0.40	$ 0.32	$ 7.34	$ 2.77	$ (1.54)
[1]	Net of income attributable to noncontrolling interests of discontinued operations of $4.3 million for the fiscal year ended September 30, 2016.

Earnings per Share (Parenthetic

Earnings per Share (Parenthetical) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2016USD ($)
Earnings Per Share [Abstract]
Net of income attributable to noncontrolling interests of discontinued operations	$ 4.3

Earnings per Share - Additional

Earnings per Share - Additional Information (Details) - shares shares in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.2	0.7	1.6
Smurfit Stone [Member]
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Common Stock, Capital Shares Reserved For Future Issuance	0	0.2	0.3	1.4

Financial Results by Quarter _3

Financial Results by Quarter (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Quarterly Financial Data [Abstract]
Net sales	$ 4,236.6	$ 4,137.5	$ 4,017	$ 3,894	$ 4,060.6	$ 3,695.6	$ 3,656.3	$ 3,447.2	$ 16,285.1	$ 14,859.7	$ 14,171.8
Cost of goods sold	3,294.9	3,264.3	3,220.4	3,111.6	3,282.6	3,000.1	2,980.9	2,855.9	12,891.2	12,119.5	11,413.2
Multiemployer pension withdrawals		4.2		180					184.2
Pension lump sum settlement					3.9		28.7			32.6
Land and Development impairments	2.6	1.7		27.6	4		42.7		31.9	46.7
Restructuring and other costs	40.3	17.1	31.7	16.3	38	59.4	18.3	81	105.4	196.7	366.4
(Loss) gain on extinguishment of debt	(0.1)	0.9	0.1	(1)	(0.1)	2	(0.1)		(0.1)	1.8	2.7
Gain on sale of HH&B					2.2	190.6				192.8
Income tax benefit (expense)	(95.4)	(84.5)	(18.8)	1,073.2					(874.5)	159	89.8
Consolidated net income (loss)	280	271.3	224.5	1,133.5	195.3	326.6	98.2	78.5	1,909.3	698.6	(389.9)
Net income attributable to common stockholders	$ 279.6	$ 268.2	$ 223.2	$ 1,135.1	$ 196.1	$ 328.1	$ 103.1	$ 80.9	$ 1,906.1	$ 708.2	$ (396.3)
Basic earnings (loss) per share attributable to common stockholders	$ 1.10	$ 1.05	$ 0.87	$ 4.45	$ 0.77	$ 1.30	$ 0.41	$ 0.32	$ 7.46	$ 2.81	$ (1.56)
Diluted earnings (loss) per share attributable to common stockholders	$ 1.08	$ 1.03	$ 0.86	$ 4.38	$ 0.76	$ 1.29	$ 0.40	$ 0.32	$ 7.34	$ 2.77	$ (1.54)

Financial Results by Quarter _4

Financial Results by Quarter (Unaudited) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Data [Abstract]
Multiemployer pension withdrawals		$ 4.2		$ 180					$ 184.2
Multiemployer Pension Withdrawal Net of Noncontrolling Interest				179.1
Land and Development impairments	$ 2.6	$ 1.7		27.6	$ 4		$ 42.7		31.9	$ 46.7
Land and Development impairments Net				25.6			$ 36.3
Provisional Estimate of Benefit (Expense) Impact on Remeasurement of Deferred Tax Balances in Connection with December 22, 2017 Income Tax Legislation			$ 36.3	$ 1,086.9					$ 1,215.9
Basic Earnings Per Share, Estimated Increase (Decrease) Due to Specific Items Occurring During Quarter				$ 3.67		$ 0.76
Diluted Earnings Per Share, Estimated Increase (Decrease) Due to Specific Items Occurring During Quarter				$ 3.61		$ 0.75
Basic and Diluted Earnings Per Share, Estimated Increase (Decrease) Due to Specific Items Occurring During Quarter			$ 0.14				$ (0.16)	$ 0.09
Effective Income Tax Rate Reconciliation, Release of State Deferred Tax Liability as a Result of Equity Restructuring, Amount								$ 23.8
Pension lump sum settlement					3.9		$ 28.7			32.6
Land and Development Impairments, Noncontrolling Interest							$ 6.4
Gain on sale of HH&B					$ 2.2	$ 190.6				$ 192.8

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Nov. 02, 2018	Oct. 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share				$ 0.01	$ 0.01
Scenario, Forecast [Member] | Hurricane Michael [Member]
Subsequent Event [Line Items]
Percentage of market pulp production capacity			50.00%
Subsequent Event [Member]
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01
Ratio of WRKCo Shares to WestRock Shares	1
Subsequent Event [Member] | Hurricane Michael [Member]
Subsequent Event [Line Items]
Property damage and business interruption claim amount		$ 100
Insurance claim deductible		$ 15
Subsequent Event [Member] | WRKCo Inc. [Member]
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01
Subsequent Event [Member] | KapStone Acquisition [Member]
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share	0.0001
Business Acquisition, Share Price	$ 35
Ratio of KapStone Shares to WestRock Shares	49.81%
Maximum percentage of issued and outstanding KapStone Shares to elect WestRock stock consideration	25.00%
Estimated Enterprise Value of Acquisition	$ 4,800
Consideration paid in cash	$ 3,300
Business acquisition, number of shares issued	1.6
Business acquisition, percentage of equity interest on shares issued and outsanding	0.60%