WestRock (WRK) 10-K 23 Nov 20 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Nov. 06, 2020	Mar. 31, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	WESTROCK COMPANY
Entity Central Index Key	0001732845
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Title of 12(b) Security	Common Stock, par value $0.01 per share
Entity Incorporation, State or Country Code	DE
Security Exchange Name	NYSE
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 7,220
Entity Common Stock, Shares Outstanding		262,653,756
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Trading Symbol	WRK
Entity File Number	001-38736
Entity Tax Identification Number	37-1880617
Entity Address, Address Line One	1000 Abernathy Road NE
Entity Address, City or Town	Atlanta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30328
City Area Code	770
Local Phone Number	448-2193
Document Annual Report	true
Document Transition Report	false

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 17,578.8	$ 18,289	$ 16,285.1
Cost of goods sold	14,381.6	14,540	12,923.1
Gross profit	3,197.2	3,749	3,362
Selling, general and administrative, excluding intangible amortization	1,624.4	1,715.2	1,546.6
Selling, general and administrative intangible amortization	400.5	400.2	296.6
(Gain) loss on disposal of assets	(16.3)	(41.2)	10.1
Multiemployer pension withdrawal (income) expense	(1.1)	(6.3)	184.2
Land and Development impairments		13	31.9
Restructuring and other costs	112.7	173.7	105.4
Goodwill impairment	1,333.2
Operating (loss) profit	(256.2)	1,494.4	1,187.2
Interest expense, net	(393.5)	(431.3)	(293.8)
Loss on extinguishment of debt	(1.5)	(5.1)	(0.1)
Pension and other postretirement non-service income	103.3	74.2	95.3
Other income, net	9.5	2.4	12.7
Equity in income of unconsolidated entities	15.8	10.1	33.5
(Loss) income before income taxes	(522.6)	1,144.7	1,034.8
Income tax (expense) benefit	(163.5)	(276.8)	874.5
Consolidated net (loss) income	(686.1)	867.9	1,909.3
Less: Net income attributable to noncontrolling interests	(4.8)	(5)	(3.2)
Net (loss) income attributable to common stockholders	$ (690.9)	$ 862.9	$ 1,906.1
Basic (loss) earnings per share attributable to common stockholders	$ (2.67)	$ 3.36	$ 7.46
Diluted (loss) earnings per share attributable to common stockholders	(2.67)	3.33	7.34
Cash dividends paid per share	$ 1.33	$ 1.82	$ 1.72

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net (loss) income	$ (686.1)	$ 867.9	$ 1,909.3
Other comprehensive (loss) income, net of tax:
Foreign currency translation loss	(215)	(143.4)	(234.4)
Derivatives:
Deferred (loss) gain on cash flow hedges	(10)	1.1	0
Reclassification adjustment of net loss (gain) on cash flow hedges included in earnings	3.6	(0.2)	0.5
Unrealized gain on available for sale security	0	0	0.8
Reclassification adjustment of gain on available for sale security included in earnings	0	0	(1.5)
Defined benefit pension and other postretirement benefit plans:
Net actuarial gain (loss) arising during period	24.2	(248.5)	(13.1)
Amortization and settlement recognition of net actuarial loss, included in pension and postretirement cost	35.4	17.2	15
Prior service cost arising during period	(19.6)	(3.3)	(5.5)
Amortization and curtailment recognition of prior service cost, included in pension and postretirement cost	3.8	1.8	0.2
Other comprehensive (loss) income, net of tax	(177.6)	(375.3)	(238)
Comprehensive (loss) income	(863.7)	492.6	1,671.3
Less: Comprehensive income attributable to noncontrolling interests	(4.5)	(3.6)	(3.2)
Comprehensive (loss) income attributable to common stockholders	$ (868.2)	$ 489	$ 1,668.1

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Sep. 30, 2020	Sep. 30, 2019
Current assets:
Cash and cash equivalents		$ 251.1	$ 151.6
Accounts receivable (net of allowances of $66.3 and $53.2)		2,142.7	2,193.2
Inventories		2,023.4	2,107.5
Other current assets		520.5	496.2
Assets held for sale		7	25.8
Total current assets		4,944.7	4,974.3
Property, plant and equipment, net		10,778.9	11,189.5
Goodwill		5,962.2	7,285.6
Intangibles, net		3,667.2	4,059.5
Restricted assets held by special purpose entities		1,267.5	1,274.3
Prepaid pension asset		368.7	224.7
Other assets		1,790.5	1,148.8
Total assets		28,779.7	30,156.7
Current liabilities:
Current portion of debt		222.9	561.1
Accounts payable		1,674.2	1,831.8
Accrued compensation and benefits		386.7	470.4
Other current liabilities		645.1	571.8
Total current liabilities		2,928.9	3,435.1
Long-term debt due after one year		9,207.7	9,502.3
Pension liabilities, net of current portion		305.2	294
Postretirement benefit liabilities, net of current portion		145.4	162.1
Non-recourse liabilities held by special purpose entities		1,136.5	1,145.2
Deferred income taxes		2,916.9	2,878
Other long-term liabilities		1,490.3	1,053.9
Commitments and contingencies (Note 18)
Redeemable noncontrolling interests		1.3	1.9
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; 260.4 million and 257.8 million shares outstanding at September 30, 2020 and September 30, 2019, respectively		2.6	2.6
Capital in excess of par value		10,916.3	10,739.4
Retained earnings		1,031.6	1,997.1
Accumulated other comprehensive loss	[1]	(1,319.9)	(1,069.2)
Total stockholders’ equity		10,630.6	11,669.9
Noncontrolling interests		16.9	14.3
Total equity		10,647.5	11,684.2
Total liabilities and equity		$ 28,779.7	$ 30,156.7
[1]	All amounts are net of tax and noncontrolling interest.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Statement Of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 66.3	$ 53.2
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	260,400,000	257,800,000

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions		Total		Common Stock [Member]		Capital in Excess of Par Value [Member]		Retained Earnings [Member]		AOCI Attributable to Parent	Noncontrolling Interests [Member]
Beginning balance at Sep. 30, 2017				254,500,000
Shares issued under restricted stock plan				700,000
Compensation expense under share-based plans						$ 66.9
Net (loss) income attributable to common stockholders								$ 1,906.1
Dividends declared (per share - $1.33, $1.82 and $1.72)	[1]							(445.2)
Issuance of common stock, net of stock received for minimum tax withholdings	[2]			1,700,000
Purchases of common stock		(3,400,000)		(3,400,000)	[3]
Other comprehensive loss, net of tax		$ (238)								$ (238)
Net income		(3.2)									$ 2.1	[4]
Contributions	[4]										0.5
Distributions and adjustments to noncontrolling interests	[4]										(33.2)
Ending balance at Sep. 30, 2018				253,500,000
Beginning balance at Sep. 30, 2017				$ 2.5		10,624.9		172.4		(457.3)	43.6	[4]
Issuance of common stock, net of stock received for minimum tax withholdings						38.9	[2]	(6.7)
Purchases of common stock		(195.1)				(141.8)	[3]	(53.3)	[3]
Ending balance at Sep. 30, 2018		11,482.4		$ 2.5		10,588.9		1,573.3		(695.3)	13	[4]
Total Stockholders’ equity at Sep. 30, 2018		$ 11,469.4
Shares issued under restricted stock plan				3,200,000
Compensation expense under share-based plans						64.8
Adoption of accounting standards	[5]							43.5
Net (loss) income attributable to common stockholders								862.9
Dividends declared (per share - $1.33, $1.82 and $1.72)	[1]							(479.8)
Issuance of common stock, net of stock received for minimum tax withholdings	[2]			3,200,000
Fair value of share-based awards issued in business combinations						70.8
Purchases of common stock		(2,100,000)		(2,100,000)	[3]
Other comprehensive loss, net of tax		$ (373.9)	[6]							(373.9)
Net income		$ (5)									3.2	[4]
Contributions	[4]										0.2
Distributions and adjustments to noncontrolling interests	[4]										(2.1)
Ending balance at Sep. 30, 2019		257,800,000		257,800,000
Issuance of common stock, net of stock received for minimum tax withholdings				$ 0.1	[2]	101.1	[2]	(0.4)
Purchases of common stock		$ (88.6)				(86.2)	[3]	(2.4)	[3]
Ending balance at Sep. 30, 2019		11,684.2		$ 2.6		10,739.4		1,997.1		(1,069.2)	14.3	[4]
Total Stockholders’ equity at Sep. 30, 2019		$ 11,669.9
Shares issued under restricted stock plan				900,000
Compensation expense under share-based plans						130.3
Adoption of accounting standards	[5]							73.5
Net (loss) income attributable to common stockholders								(690.9)
Dividends declared (per share - $1.33, $1.82 and $1.72)	[1]							(348.1)
Issuance of common stock, net of stock received for minimum tax withholdings	[2]			1,700,000
Purchases of common stock		0
Adoption of new standard and reclassification of stranded tax effects resulting from Tax Reform										(73.4)
Other comprehensive loss, net of tax		$ (177.3)	[6]							(177.3)
Net income		$ (4.8)									2.7	[4]
Distributions and adjustments to noncontrolling interests	[4]										(0.1)
Ending balance at Sep. 30, 2020		260,400,000		260,400,000
Issuance of common stock, net of stock received for minimum tax withholdings	[2]					46.6
Ending balance at Sep. 30, 2020		$ 10,647.5		$ 2.6		$ 10,916.3		$ 1,031.6		$ (1,319.9)	$ 16.9	[4]
Total Stockholders’ equity at Sep. 30, 2020		$ 10,630.6
[1]	Includes cash dividends paid and dividend equivalent units on certain restricted stock awards.
[2]	Included in the issuance of common stock in fiscal 2019 is the issuance of approximately 1.6 million shares of Common Stock valued at $70.1 million in connection with the KapStone Acquisition.
[3]	In fiscal 2019, we repurchased approximately 2.1 million shares of our Common Stock for an aggregate cost of $88.6 million. In fiscal 2018, we repurchased approximately 3.4 million shares of our Common Stock for an aggregate cost of $195.1 million.
[4]	Excludes amounts related to contingently redeemable noncontrolling interests, which are separately classified outside of permanent equity in the Consolidated Balance Sheets.
[5]	For fiscal 2020, the amount primarily relates to the adoption of ASU 2018-02 (as hereinafter defined). For fiscal 2019, the amount relates to the adoption of ASC 606 (as hereinafter defined).
[6]	All amounts are net of tax and noncontrolling interest.

CONSOLIDATED STATEMENTS OF EQ_2

CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares
Cash dividends paid per share | $ / shares	$ 1.82
Purchases of common stock	2,100,000
Aggregate cost for purchase of common stock | $	$ 88.6
Common Stock [Member]
Purchases of common stock	2,100,000
KapStone [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	1,600,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable | $	$ 70.1

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Consolidated net (loss) income	$ (686,100,000)	$ 867,900,000	$ 1,909,300,000
Adjustments to reconcile consolidated net income to net cash provided by operating activities:
Depreciation, depletion and amortization	1,487,000,000	1,511,200,000	1,252,200,000
Cost of real estate sold	16,100,000	17,300,000	121,200,000
Deferred income tax expense (benefit)	43,000,000	37,100,000	(1,069,400,000)
Share-based compensation expense	130,300,000	64,200,000	66,800,000
401(k) match in common stock	20,800,000
Pension and other postretirement funding more than expense (income)	(80,100,000)	(61,300,000)	(96,800,000)
Multiemployer pension withdrawal (income) expense	(1,100,000)	(6,300,000)	184,200,000
Land and Development impairments		13,000,000	31,900,000
Goodwill impairment	1,333,200,000
Other impairment adjustments	25,800,000	38,300,000	13,500,000
(Gain) loss on disposal of plant, equipment and other, net	(13,200,000)	(43,000,000)	2,900,000
Other	(39,300,000)	(80,200,000)	(96,300,000)
Change in operating assets and liabilities, net of acquisitions and divestitures:
Accounts receivable	30,500,000	272,900,000	(580,100,000)
Inventories	21,800,000	(110,500,000)	(72,100,000)
Other assets	(202,400,000)	(124,600,000)	(67,700,000)
Accounts payable	(86,400,000)	(39,100,000)	180,300,000
Income taxes	(27,600,000)	7,200,000	130,600,000
Accrued liabilities and other	98,400,000	(53,900,000)	20,700,000
Net cash provided by operating activities	2,070,700,000	2,310,200,000	1,931,200,000
Investing activities:
Capital expenditures	(978,100,000)	(1,369,100,000)	(999,900,000)
Cash paid for purchase of businesses, net of cash acquired		(3,374,200,000)	(239,900,000)
Cash receipts on sold trade receivables			461,600,000
Investment in unconsolidated entities	(1,300,000)	(11,200,000)	(114,300,000)
Proceeds from sale of property, plant and equipment	35,000,000	119,100,000	23,300,000
Proceeds from property, plant and equipment insurance settlement	6,500,000	25,500,000	7,900,000
Other	16,400,000	30,300,000	46,200,000
Net cash used for investing activities	(921,500,000)	(4,579,600,000)	(815,100,000)
Financing activities:
Proceeds from issuance of notes	598,600,000	2,498,200,000	1,197,300,000
Additions to revolving credit facilities	428,000,000	222,200,000	702,400,000
Repayments of revolving credit facilities	(528,200,000)	(227,200,000)	(572,200,000)
Additions to debt	696,400,000	5,061,600,000	855,200,000
Repayments of debt	(1,449,200,000)	(5,631,600,000)	(2,032,900,000)
Changes in commercial paper, net	(339,200,000)	339,200,000
Other financing (repayments) additions	(80,300,000)	52,200,000	(269,900,000)
Issuances of common stock, net of related minimum tax withholdings	22,200,000	18,300,000	26,600,000
Purchases of common stock	0	(88,600,000)	(195,100,000)
Cash dividends paid to stockholders	(344,500,000)	(467,900,000)	(440,900,000)
Cash distributions paid to noncontrolling interests	(2,400,000)	(4,300,000)	(33,300,000)
Other	(22,500,000)	8,100,000	7,700,000
Net cash (used for) provided by financing activities	(1,021,100,000)	1,780,200,000	(755,100,000)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(28,600,000)	4,000,000	(28,200,000)
Increase (decrease) in cash, cash equivalents and restricted cash	99,500,000	(485,200,000)	332,800,000
Cash, cash equivalents and restricted cash at beginning of period	151,600,000	636,800,000	304,000,000
Cash, cash equivalents and restricted cash at end of period	251,100,000	151,600,000	636,800,000
Supplemental disclosure of cash flow information:
Income taxes, net of refunds	147,200,000	226,100,000	60,500,000
Interest, net of amounts capitalized	$ 395,400,000	$ 412,500,000	$ 284,400,000

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
Non-cash investing activities:
Deferred purchase price of trade receivables sold	$ 436.7

CONSOLIDATED STATEMENTS OF CA_3

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical 1) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Statement Of Cash Flows [Abstract]
Fair value of assets acquired, including goodwill	$ 5,948.9	$ 303.2
Cash consideration for the purchase of businesses, net of cash acquired	(3,369.3)	(242.1)
Stock issued in business combinations	(70.1)
Fair value of share-based awards issued in business combinations	(70.8)
Deferred payments and (unpaid) unreceived working capital or escrow	16.6	(25)
Liabilities and noncontrolling interest assumed	$ 2,455.3	$ 36.1

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Sep. 30, 2020
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 Company WestRock is a multinational provider of sustainable fiber-based paper and packaging. 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. On November 2, 2018, we completed the KapStone Acquisition. 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 U.S., Canada and Mexico. KapStone is reported in our Corrugated Packaging segment. WRKCo (formerly known as WestRock Company) was the accounting acquirer in the transaction; therefore, the historical consolidated financial statements of WRKCo for periods prior to the KapStone Acquisition are also considered to be the historical financial statements of the Company. See “ Note 3. Acquisitions and Investments Basis of Presentation and Principles of Consolidation The consolidated financial statements are prepared in accordance with GAAP and, in certain cases, include amounts based on management's prudent judgments and estimates. Actual results may differ from these estimates. The consolidated financial statements include the accounts of WestRock and our partially owned subsidiaries for which we have a controlling financial interest, including variable interest entities for which we are the primary beneficiary. 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 without a readily determinable value in which we are not able to exercise significant influence over the investee are accounted under the measurement alternative (i.e. cost less impairment, adjusted for any qualifying observable price changes). Our equity and cost method investments are not material either individually or in the aggregate. We have eliminated all significant intercompany accounts and transactions. See “ Note 7. Segment Information Reclassifications and Adjustments During fiscal 2020, we evaluated our revolving credit facilities and determined that the borrowings and repayments for certain facilities should be presented gross instead of net on the consolidated statements of cash flow and corrected the presentation of the prior years by an immaterial amount. Certain amounts in prior periods have been reclassified to conform with the 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 estimating the fair value of assets and liabilities of acquired businesses. 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. The global impact of the COVID-19 pandemic may also affect our accounting estimates, which may materially change from period to period due to changing market factors. We regularly evaluate these significant factors and make adjustments where facts and circumstances dictate. Revenue Recognition We generally recognize revenue on a point-in-time basis when the customer takes title to the goods and assumes the risks and rewards for the goods, which coincide with the transfer of control of our goods to the customer. Additionally, we manufacture certain customized products that have no alternative use to us (since they 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 products, including a reasonable profit. For products that meet these two criteria, we recognize revenue “over time”. This results in revenue recognition prior to the date of shipment or title transfer for these products and increases the contract asset (unbilled receivables) balance with a corresponding reduction in finished goods inventory on our balance sheet. We net, against our gross sales, provisions for discounts, returns, allowances, customer rebates and other adjustments. Such adjustments are based on historical experience which is consistent with the most likely method as provided in ASC 606 “ Revenue from Contracts with Customers ASC 606 As permitted by ASC 606, we have elected to treat costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset we would recognize is one year or less. We do not record interest income when the difference in timing of control transfer and customer payment is one year or less. We also 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. 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 since we treat shipping and handling as fulfilment activities. 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 of our cash and cash equivalents approximate fair market values. We place our cash and cash equivalents primarily 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 average of our receivables collection is within 30 to 60 days. We sell certain receivables under our A/R Sales Agreement (as hereinafter defined). See “ Note 12. Fair Value — Accounts Receivable 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 charge off receivables when they are determined to be no longer collectible. Bad debt expense was $19.9 million, $10.0 million and $4.2 million in fiscal 2020, 2019 and 2018, respectively. 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 2020, 2019 and 2018 (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 53.2 $ 49.7 $ 45.8 Reduction in sales and charges to costs and expenses 270.8 259.6 202.8 Deductions (257.7 ) (256.1 ) (198.9 ) Balance at end of fiscal year $ 66.3 $ 53.2 $ 49.7 Inventories We value our U.S. inventories at the lower of cost or market, with cost for the majority of our U.S. inventories determined on the last-in first-out (“ LIFO 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. Leased Assets We adopted the provisions of ASC 842 on October 1, 2019 using the modified retrospective approach and, as a result, did not restate prior periods. See “ Note 15. Leases ” for additional details. We record our operating lease ROU assets and liabilities at the commencement date of the lease based on the present value of lease payments over the lease term. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Our leases may include options to extend or terminate the lease. These options to extend are included in the lease term when it is reasonably certain that we will exercise that option. While some leases provide for variable payments, they are not included in the ROU assets and liabilities because they are not based on an index or rate. Variable payments for real estate leases primarily relate to common area maintenance, insurance, taxes and utilities. Variable payments for equipment, vehicles and leases within supply agreements primarily relate to usage, repairs, and maintenance. As the implicit rate is not readily determinable for our leases, we apply a portfolio approach using an estimated incremental borrowing rate to determine the initial present value of lease payments over the lease terms on a collateralized basis over a similar term, which is based on market and company specific information. We use the unsecured borrowing rate and risk-adjust that rate to approximate a collateralized rate, and apply the rate based on the currency of the lease, which is updated on a quarterly basis for measurement of new lease liabilities. We have made an accounting policy election to not recognize ROU assets and liability for leases with a term of 12 months or less unless the lease includes an option to renew or purchase the underlying asset that are reasonably certain to be exercised. In addition, the Company has applied the practical expedient to account for the lease and non-lease components as a single lease component for all of the Company's leases. See “ Note 15. Leases ” for additional information . Property, Plant and Equipment We record 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 2020, 2019 and 2018, we capitalized interest of approximately $24.6 million, $23.8 million and $8.2 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 useful 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.” ASC 350 allows an optional qualitative assessment, prior to a quantitative assessment test, to determine whether it is more likely than not that the fair value of a reporting unit exceeds its carrying amount. We generally do not attempt a qualitative assessment and move directly to the quantitative test. As part of the quantitative test, we utilize the present value of expected cash flows or, as appropriate, a combination of the present value of expected 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 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 past 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, which we believe would be generally consistent with that of a market participant. 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 are 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 is 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 measure goodwill impairment charge based on the excess of a reporting unit’s carrying amount over its fair value as required under ASU 2017-04, which we early adopted starting with our fiscal 2020 annual goodwill impairment test on July 1, 2020. We began seeing the impact of COVID-19 in a limited manner at the end of the second quarter of fiscal 2020. The impact on our operations increased in the third quarter of fiscal 2020. During these interim periods, we evaluated the current economic environment, including our then current assessment of the long-term impact of COVID-19 on our forecasts, and we concluded there were no indicators of impairment of our long-lived assets, including goodwill that required a quantitative test to be performed. During the fourth quarter of fiscal 2020, we completed our annual goodwill impairment testing. We considered factors such as, but not limited to, our expectations for the short-term and long-term impacts of COVID-19, macroeconomic conditions, industry and market considerations, and financial performance, including planned revenue, earnings and capital investments of each reporting unit. 10% The impairment was driven by the expected lower volumes and cash flows related to certain external SBS end markets, including commercial print, tobacco and plate and cup stock markets e believe these declines are more systemic and our view of related growth and earnings opportunities has been diminished for the foreseeable future. “ Risk Factors ” We follow the provisions included in ASC 360, “Property, Plant and Equipment” greater than the fair value of the asset. We estimate fair value using discounted cash flows, observable prices for similar assets, or other valuation techniques. We record assets classified as “held for sale” at the lower of their carrying value or estimated fair value less anticipated costs to sell. 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 15.5 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 likely that we will 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, contractual obligations, and the adjustments of property, plant and equipment and lease ROU assets to their fair 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 4. Restructuring and Other Costs Business Combinations From time to time, we may enter into business combinations. In accordance with ASC 805, “ Business Combinations The acquisition method of accounting also requires us to refine these estimates over a measurement period not to exceed one year to reflect new information obtained about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date. If we are required to adjust provisional amounts that we have recorded for the fair values of assets and liabilities in connection with acquisitions, these adjustments could have a material impact on our financial condition and results of operations. 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 future 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 5. Retirement Plans ” Supplemental Plans We measure certain nonfinancial assets and nonfinancial liabilities at fair value on a nonrecurring basis. These assets and liabilities include equity method investments when they are deemed to be other-than-temporarily impaired, investments for which the fair value measurement alternative is elected, assets acquired and liabilities assumed 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, property, plant and equipment, ROU assets related to operating leases, goodwill and other intangible assets that are written down to fair value when they are held for sale or determined to be impaired. See “ Note 4. Restructuring and Other Costs “ 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 entire change in fair value of 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. 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, 2020, the notional amounts of interest rate and foreign currency exchange contract derivatives were $600.0 million and $250.2 million, respectively. The fair value of these derivative instruments was not significant as of September 30, 2020. At September 30, 2020, no natural gas commodity derivatives were outstanding. At September 30, 2019, the notional amounts of interest rate and foreign currency exchange contract derivatives were $600.0 million and $351.0 million, respectively. At September 30, 2019, the notional amount of natural gas commodity derivatives was 8.4 MMBtu. 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 . 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 (as hereinafter defined) was signed into law. The Tax Act contained 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 6. Income Taxes. Pension and Other Postretirement Benefits We account for pension and other postretirement benefits in accordance with ASC 715, “ Compensation – Retirement Benefits “ Note 5. 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 WestRock Pandemic Action Plan we issued restricted stock grants to the majority of our employees to replace their annual cash bonus. See “ Note 21. Share-Based Compensation ” for additional information. Asset Retirement Obligations We account 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, 2020 and 2019 were $118.2 million and $124.3 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

Revenue Recognition

Revenue Recognition	12 Months Ended
	Sep. 30, 2020
Revenue From Contract With Customer [Abstract]
Revenue Recognition	Note 2. Revenue Recognition Disaggregated Revenue ASC 606 requires that we disaggregate revenue from contracts with customers into categories that depict how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The tables below disaggregate our revenue by geographical market and product type (segment). Net sales are attributed to geographical markets based on our selling location. Year Ended September 30, 2020 (In millions) Corrugated Packaging Consumer Packaging Land and Development Intersegment Sales Total Primary Geographical Markets North America $ 10,975.8 $ 4,978.2 $ 18.9 $ (191.4 ) $ 15,781.5 South America 393.1 70.1 — — 463.2 Europe 7.9 1,006.4 — (0.3 ) 1,014.0 Asia Pacific 42.4 278.3 — (0.6 ) 320.1 Total $ 11,419.2 $ 6,333.0 $ 18.9 $ (192.3 ) $ 17,578.8 Year Ended September 30, 2019 (In millions) Corrugated Packaging Consumer Packaging Land and Development Intersegment Sales Total Primary Geographical Markets North America $ 11,314.7 $ 5,166.6 $ 23.4 $ (155.5 ) $ 16,349.2 South America 437.2 73.2 — — 510.4 Europe 1.6 1,064.7 — (0.1 ) 1,066.2 Asia Pacific 63.2 301.5 — (1.5 ) 363.2 Total $ 11,816.7 $ 6,606.0 $ 23.4 $ (157.1 ) $ 18,289.0 Revenue Contract Balances Contract assets are rights to consideration in exchange for goods that we have transferred to a customer when that right is conditional on something other than the passage of time. Contract assets are reduced when the control of the goods passes to the customer. Contract liabilities represent obligations to transfer goods or services to a customer for which we have received consideration. Contract liabilities are reduced once control of the goods is transferred to the customer. The opening and closing balances of our contract assets and contract liabilities are as follows. Contract assets and contract liabilities are reported within Other current assets and Other current liabilities, respectively, on the consolidated balance sheet. (In millions) Contract Assets (Short-Term) Contract Liabilities (Short-Term) Beginning balance - October 1, 2019 $ 188.0 $ 7.7 Ending balance - September 30, 2020 185.8 12.0 (Decrease) / increase $ (2.2 ) $ 4.3 Performance Obligations and Significant Judgments We primarily derive revenue from fixed consideration. Certain contracts may also include variable consideration, typically in the form of cash discounts and volume rebates. If a contract with a customer includes variable consideration, we estimate the expected cash discounts and other customer refunds based on historical experience. We concluded this method is consistent with the most likely amount method under ASC 606 and allows us to make the best estimate of the consideration we will be entitled to from customers. Contracts or purchase orders with customers could include a single type of product or multiple types and grades of products. Regardless, the contract price with the customer is agreed to at the individual product level outlined in the customer contracts or purchase orders. Management has concluded that the prices negotiated with each individual customer are representative of the stand-alone selling price of the product.

Acquisitions and Investments

Acquisitions and Investments	12 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Acquisitions and Investments	Note 3. Acquisitions and Investments 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 2020 to our fiscal 2019 provisional fair value estimates of assets and liabilities assumed in acquisitions were significant. The measurement periods for all prior acquisitions are closed. KapStone Acquisition On November 2, 2018, we completed the KapStone Acquisition. Effective as of the effective time of the KapStone Acquisition (the “ Effective Time 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 U.S., Canada and Mexico. We have included the financial results of KapStone in our Corrugated Packaging segment since the date of the acquisition. Pursuant to the KapStone Acquisition, at the Effective Time, (a) each issued and outstanding share of common stock, par value $0.01 per share, of WRKCo was converted into one share of common stock, par value $0.01 per share, of the Company (“ Company common stock KapStone common stock Cash Consideration Stock Consideration Maximum Stock Amount The consideration for the KapStone Acquisition was $4.9 billion including debt assumed, a long-term financing obligation and assumed equity awards. As a result, KapStone stockholders received in the aggregate approximately $3.3 billion in cash and 1.6 million shares of WestRock common stock with a value of $70.1 million, 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. Included in the consideration was $70.8 million related to outstanding KapStone equity awards that were replaced with WestRock equity awards with identical terms for pre-combination service. The amount related to post-combination service will be expensed over the remaining service period of the awards. See “ Note 21. Share-Based Compensation ” for additional information on the converted awards. The following table summarizes the fair values of the assets acquired and liabilities assumed in the KapStone Acquisition by major class of assets and liabilities as of the acquisition date, as well as adjustments made during fiscal 2019 and fiscal 2020 (referred to as “ measurement period adjustments Amounts Recognized as of the Acquisition Date Measurement Period Adjustments (1) Amounts Recognized as of Acquisition Date (as Adjusted) (2) Cash and cash equivalents $ 8.6 $ — $ 8.6 Current assets, excluding cash and cash equivalents 878.9 (30.2 ) 848.7 Property, plant and equipment, net 1,910.3 11.5 1,921.8 Goodwill 1,755.0 0.5 1,755.5 Intangible assets 1,336.1 30.3 1,366.4 Other long-term assets 27.9 (0.1 ) 27.8 Total assets acquired 5,916.8 12.0 5,928.8 Current portion of debt 33.3 — 33.3 Current liabilities 337.5 7.9 345.4 Long-term debt due after one year 1,333.4 — 1,333.4 Accrued pension and other long-term benefits 9.8 2.8 12.6 Deferred income taxes 609.7 (1.4 ) 608.3 Other long-term liabilities 118.4 2.7 121.1 Total liabilities assumed 2,442.1 12.0 2,454.1 Net assets acquired $ 3,474.7 $ — $ 3,474.7 (1) (2) The measurement period adjustments were primarily due to refinements to third party appraisals and carrying amounts of certain assets and liabilities, as well as adjustments to certain tax accounts based on, among other things, adjustments to deferred tax liabilities. The net impact of the measurement period adjustments to goodwill were essentially flat. The fair value assigned to goodwill is primarily attributable to buyer-specific synergies expected to arise after the KapStone Acquisition (e.g., enhanced geographic reach of the combined organization, increased vertical integration and other synergistic opportunities) and the assembled work force of KapStone, as well as from establishing deferred tax liabilities for the assets and liabilities acquired. The goodwill and intangible assets resulting from the acquisition are not amortizable for tax purposes. The following table summarizes the weighted average life and the fair value of intangible assets recognized in the KapStone Acquisition, excluding goodwill (in millions, except lives): Weighted Avg. Life Amounts Recognized as of the Acquisition Date Customer relationships 11.7 $ 1,303.0 Trademarks and tradenames 16.9 54.2 Favorable contracts 6.0 9.2 Total 11.9 $ 1,366.4 None of the intangible assets have significant residual value. The intangible assets are expected to be amortized over estimated useful lives ranging from one to 20 years based on the approximate pattern in which the economic benefits are consumed or straight-line if the pattern was not reliably determinable. Schlüter Acquisition On September 4, 2018, we completed the acquisition of Schlüter Print Pharma Packaging (the " Schlüter Acquisition In connection with the Schlüter Acquisition, we paid cash of $50.6 million. The purchase consideration included the assumption of $7.5 million of debt. since the date of the acquisition The allocation of consideration primarily included $9.1 million of customer relationship intangible assets, $23.7 million of goodwill, $26.5 million of property, plant and equipment and $21.1 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 tax liabilities 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. Plymouth Packaging Acquisition On January 5, 2018, we completed the acquisition (the “ Plymouth Packaging Acquisition ”) of substantially all of the assets of Plymouth Packaging, Inc. (“ Plymouth ”) 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 purchase price of $203.9 million, net of cash received of $3.1 million. We have included the financial results of the acquired assets in our Corrugated Packaging segment . The allocation of consideration primarily included $61.9 million of customer relationship intangible assets, $59.6 million of goodwill, $36.2 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 tax liabilities for the difference between book and tax basis of the assets and liabilities acquired. The goodwill and intangibles are amortizable for income tax purposes. 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. On October 20, 2017, we increased our ownership interest in Grupo Gondi in Mexico (the “ Joint Venture ”) “Partners interest, the Partners may elect to sell us the Partners’ remaining interest at fair market value at that time, or a portion thereof in the future in accordance with the terms of the option agreement .

Restructuring and Other Costs

Restructuring and Other Costs	12 Months Ended
	Sep. 30, 2020
Restructuring And Other Costs [Abstract]
Restructuring and Other Costs	Note 4. Restructuring and Other Costs Summary of Restructuring and Other Initiatives We recorded pre-tax restructuring and other costs of $112.7 million, $173.7 million and $105.4 million for fiscal 2020, 2019 and 2018, respectively. Of these costs, $29.8 million, $56.5 million and $27.0 The following table summarizes our Restructuring and other costs for fiscal 2020, 2019 and 2018 (in millions): 2020 2019 2018 Restructuring $ 93.7 $ 111.0 $ 39.5 Other 19.0 62.7 65.9 Restructuring and Other Costs $ 112.7 $ 173.7 $ 105.4 Restructuring Our restructuring charges are primarily associated with restructuring portions of our operations (i.e. partial or complete plant closures), employee costs due to merger and acquisition-related workforce reductions and voluntary retirement programs in fiscal 2019 and 2020. A partial plant closure may consist of shutting down a machine and/or a workforce reduction. In fiscal 2020, our restructuring charges include those associated with reducing the capacity of our Consumer mill system with the announced shutdown of an SBS machine at our Evadale, TX mill. In fiscal 2019, charges include those associated with reducing the linerboard capacity of our Corrugated mill system related to the announced shutdown of a machine at our North Charleston, SC mill. In addition, in fiscal 2019, we began recording charges in our Corrugated Packaging segment associated with the replacement of three paper machines at our Florence, SC mill with a new one. When we close a facility, if necessary, we recognize a write-down to reduce the carrying value of related property, plant and equipment and lease ROU assets to their fair value and record charges for severance and other employee-related costs. We reduce the carrying value of the assets classified as held for sale to their estimated fair value less cost to sell. Any subsequent change in fair value less cost to sell prior to disposition is recognized as it is identified; however, no gain is recognized in excess of the cumulative loss previously recorded unless the actual selling price exceeds the original carrying value. For plant closures, we also generally expect to record costs for equipment relocation, facility carrying costs and costs to terminate a lease or contract before the end of its term. 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 generally transfer 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 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): 2020 2019 2018 Cumulative Total Expected Corrugated Packaging Net property, plant and equipment costs $ 2.2 $ 32.1 $ 2.9 $ 96.3 $ 96.3 Severance and other employee costs 8.7 16.9 1.9 43.2 43.2 Equipment and inventory relocation costs 2.2 4.8 3.4 10.4 10.9 Facility carrying costs 2.6 3.9 3.3 21.1 23.2 Other costs (1.9 ) 1.2 0.1 3.3 3.3 Restructuring total $ 13.8 $ 58.9 $ 11.6 $ 174.3 $ 176.9 Consumer Packaging Net property, plant and equipment costs $ 23.5 $ 0.5 $ 6.8 $ 53.1 $ 53.1 Severance and other employee costs 19.8 6.0 6.9 58.3 58.3 Equipment and inventory relocation costs 1.4 1.0 2.4 7.3 7.3 Facility carrying costs — 0.2 0.9 1.9 1.9 Other costs 10.5 4.3 2.0 19.1 19.4 Restructuring total $ 55.2 $ 12.0 $ 19.0 $ 139.7 $ 140.0 Land and Development Net property, plant and equipment costs $ — $ — $ — $ 1.8 $ 1.8 Severance and other employee costs — 0.1 0.3 13.8 13.8 Other costs 2.0 — 3.0 5.0 5.0 Restructuring total $ 2.0 $ 0.1 $ 3.3 $ 20.6 $ 20.6 Corporate Severance and other employee costs $ 21.1 $ 37.5 $ 0.8 $ 59.4 $ 59.4 Other costs 1.6 2.5 4.8 9.0 9.0 Restructuring total $ 22.7 $ 40.0 $ 5.6 $ 68.4 $ 68.4 Total Net property, plant and equipment costs $ 25.7 $ 32.6 $ 9.7 $ 151.2 $ 151.2 Severance and other employee costs 49.6 60.5 9.9 174.7 174.7 Equipment and inventory relocation costs 3.6 5.8 5.8 17.7 18.2 Facility carrying costs 2.6 4.1 4.2 23.0 25.1 Other costs 12.2 8.0 9.9 36.4 36.7 Restructuring total $ 93.7 $ 111.0 $ 39.5 $ 403.0 $ 405.9 We have defined “ Net property, plant and equipment costs Note 4 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 and labor. Divestiture costs consist primarily of similar professional fees. 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, integration and divestiture costs that we incurred during the last three fiscal years (in millions): 2020 2019 2018 Acquisition costs $ 0.2 $ 28.2 $ 38.2 Integration costs 18.7 34.3 27.4 Divestiture costs 0.1 0.2 0.3 Other total $ 19.0 $ 62.7 $ 65.9 The following table summarizes the changes in the restructuring accrual, which is primarily composed of 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 income for the last three fiscal years (in millions): 2020 2019 2018 Accrual at beginning of fiscal year $ 32.3 $ 31.6 $ 47.4 Additional accruals 51.3 60.0 16.5 Payments (56.6 ) (55.9 ) (29.8 ) Adjustment to accruals (6.2 ) (3.2 ) (1.0 ) Foreign currency rate changes and other (3.6 ) (0.2 ) (1.5 ) Accrual at end of fiscal year $ 17.2 $ 32.3 $ 31.6 Reconciliation of accruals and charges to restructuring and other costs (in millions): 2020 2019 2018 Additional accruals and adjustments to accruals (see table above) $ 45.1 $ 56.8 $ 15.5 Acquisition costs 0.2 28.2 38.2 Integration costs 18.7 34.3 22.0 Divestiture costs 0.1 0.2 0.3 Net property, plant and equipment 25.7 32.6 9.7 Severance and other employee costs 1.6 6.8 1.3 Equipment and inventory relocation costs 3.6 5.8 5.8 Facility carrying costs 2.6 4.1 4.2 Other costs (1) 15.1 4.9 8.4 Total restructuring and other costs, net $ 112.7 $ 173.7 $ 105.4 (1)

Retirement Plans

Retirement Plans	12 Months Ended
	Sep. 30, 2020
Retirement Plans [Abstract]
Retirement Plans	Note 5. 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, and nearly all of our remaining salaried and non-union hourly employees accruing benefits will cease accruing benefits as of December 31, 2020. In addition, we participate in several MEPPs that provide retirement benefits to certain union employees in accordance with various CBAs. 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 materially 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. Our target asset allocations by asset category at September 30 were as follows: Pension Plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Equity investments 19 % 20 % 15 % 20 % Fixed income investments 75 % 72 % 75 % 72 % Short-term investments 1 % 2 % 1 % 1 % Other investments 5 % 6 % 9 % 7 % Total 100 % 100 % 100 % 100 % Our asset allocations by asset category at September 30 were as follows: Pension Plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Equity investments 22 % 21 % 13 % 22 % Fixed income investments 72 % 72 % 70 % 71 % Short-term investments 3 % 2 % 9 % 2 % Other investments 3 % 5 % 8 % 5 % 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 as well as applicable legislation in Canada and other foreign countries. Our investment policy objectives include maximizing long-term returns at acceptable risk levels, diversifying among asset classes, as applicable, and among investment managers, as well as establishing certain risk parameters within asset classes. We have allocated our investments within the equity and fixed income asset classes to sub-asset classes designed to meet these objectives. In addition, our other investments support multi-strategy objectives. 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 $23 million to our U.S. and non-U.S. pension plans in fiscal 2021. 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 or adjustments to those accruals. The weighted average assumptions used to measure the benefit plan obligations at September 30, were: Pension Plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.01 % 2.16 % 3.35 % 2.42 % Rate of compensation increase 2.50 % 2.68 % 3.00 % 2.65 % At September 30, 2020, 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, 2020 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 2021, our expected rate of return used to determine net periodic benefit cost is 6.00% for our U.S. plans and 3.73% for our non-U.S. plans. Our expected rates of return in fiscal 2021 are based on an analysis of our long-term expected rate of return and our current asset allocation. In December 2019, the USW ratified a new master agreement that applies to substantially all of our U.S. facilities represented by the USW. The agreement has a four-year term and covers a number of specific items, including wages, medical coverage and certain other benefit programs, substance abuse testing, and safety. 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 master agreement permits us to apply its terms to USW employees who work at facilities we acquire during the term of the agreement, including most former MeadWestvaco Corporation, KapStone and other acquired facilities. The following table shows the changes in benefit obligation, plan assets and funded status for the years ended September 30 (in millions): Pension Plans 2020 2019 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 $ 5,048.9 $ 1,443.1 $ 3,783.5 $ 1,340.2 Service cost 44.2 8.4 36.0 6.8 Interest cost 165.0 33.6 189.2 43.4 Amendments 25.2 (0.2 ) 0.4 3.1 Actuarial loss 214.3 41.9 694.4 181.0 Plan participant contributions — 2.0 — 2.2 Benefits paid (233.1 ) (72.0 ) (216.8 ) (78.3 ) Business combinations — — 561.2 0.7 Curtailments — 3.2 1.0 — Settlements — (9.0 ) — (1.7 ) Foreign currency rate changes — 20.5 — (54.3 ) Benefit obligation at end of fiscal year $ 5,264.5 $ 1,471.5 $ 5,048.9 $ 1,443.1 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ 5,005.3 $ 1,400.9 $ 3,921.2 $ 1,350.2 Actual gain on plan assets 582.6 65.4 731.7 172.9 Employer contributions 14.9 7.6 13.0 12.1 Plan participant contributions — 2.0 — 2.2 Benefits paid (233.1 ) (72.0 ) (216.8 ) (78.3 ) Business combinations — — 556.2 — Settlements — (9.0 ) — (1.7 ) Foreign currency rate changes — 23.1 — (56.5 ) Fair value of plan assets at end of fiscal year $ 5,369.7 $ 1,418.0 $ 5,005.3 $ 1,400.9 Funded status $ 105.2 $ (53.5 ) $ (43.6 ) $ (42.2 ) Amounts recognized in the consolidated balance sheet: Prepaid pension asset $ 290.6 $ 78.1 $ 143.3 $ 81.4 Other current liabilities (10.7 ) (1.1 ) (14.6 ) (1.9 ) Pension liabilities, net of current portion (174.7 ) (130.5 ) (172.3 ) (121.7 ) Over (under) funded status at end of fiscal year $ 105.2 $ (53.5 ) $ (43.6 ) $ (42.2 ) Certain U.S. plans have benefit obligations in excess of plan assets. These plans, which consist primarily of non-qualified plans, have aggregate projected benefit obligations of $222.3 million, aggregate accumulated benefit obligations of $222.2 million, and aggregate fair value of plan assets of $36.8 million at September 30, 2020. Our qualified U.S. plans were in a net overfunded position at September 30, 2020. The accumulated benefit obligation of U.S. and non-U.S. pension plans was $6,682.2 million and $6,438.9 million at September 30, 2020 and 2019, 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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial loss $ 753.2 $ 188.6 $ 854.7 $ 168.8 Prior service cost 45.6 2.4 27.6 3.4 Total accumulated other comprehensive loss $ 798.8 $ 191.0 $ 882.3 $ 172.2 The pre-tax amounts recognized in other comprehensive loss (income), including noncontrolling interest, are as follows at September 30 (in millions): Pension Plans 2020 2019 2018 Net actuarial (gain) loss arising during period $ (26.2 ) $ 312.0 $ 38.7 Amortization and settlement recognition of net actuarial loss (48.2 ) (25.3 ) (20.6 ) Prior service cost arising during period 25.0 3.5 9.3 Amortization of prior service cost (7.8 ) (5.2 ) (4.7 ) Net other comprehensive (income) loss recognized $ (57.2 ) $ 285.0 $ 22.7 The net periodic pension (income) cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Pension Plans 2020 2019 2018 Service cost $ 52.6 $ 42.8 $ 44.8 Interest cost 198.6 232.6 204.6 Expected return on plan assets (362.3 ) (340.2 ) (328.4 ) Amortization of net actuarial loss 46.8 24.5 21.2 Amortization of prior service cost 7.5 5.2 4.7 Curtailment loss (gain) 0.4 1.0 (0.6 ) Settlement loss (gain) 1.4 (0.2 ) (0.5 ) Company defined benefit plan (income) cost (55.0 ) (34.3 ) (54.2 ) Multiemployer and other plans 2.0 1.4 1.4 Net pension (income) cost $ (53.0 ) $ (32.9 ) $ (52.8 ) The Multiemployer and other plans line in the table above excludes the estimated withdrawal liabilities recorded. See “ Note 5. Retirement Plans — Multiemployer Plans The Consolidated Statements of Operations line item “Pension and other postretirement non-service income” is equal to the non-service elements of our “Company defined benefit plan (income) cost” and our “Net postretirement cost” outlined in this note. Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Pension Plans 2020 2019 2018 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.35 % 2.42 % 4.50 % 3.42 % 4.09 % 3.26 % Rate of compensation increase 3.00 % 2.65 % 3.00 % 2.67 % 3.00 % 2.65 % Expected long-term rate of return on plan assets 6.25 % 4.26 % 6.50 % 4.69 % 6.50 % 4.98 % For our U.S. pension and postretirement plans, we considered the mortality tables and improvement scales published by the Society of Actuaries (“ SOA For our Canadian pension and postretirement plans, we utilized the 2014 Private Sector Canadian Pensioners Mortality Table adjusted to reflect industry and our mortality experience for fiscal 2020, 2019 and 2018. As of September 30, 2020, these adjustment factors were updated to reflect the most recent mortality experience. The estimated losses that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2021 are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Actuarial loss $ 20.9 $ 10.4 Prior service cost 7.8 0.2 Total $ 28.7 $ 10.6 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 2021 $ 264.6 $ 71.9 Fiscal 2022 $ 273.5 $ 71.5 Fiscal 2023 $ 277.6 $ 71.7 Fiscal 2024 $ 282.0 $ 71.0 Fiscal 2025 $ 278.0 $ 71.3 Fiscal Years 2026 – 2030 $ 1,422.0 $ 350.0 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2020 (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) $ 253.0 $ 253.0 $ — Non-U.S. equities (1) 4.0 4.0 — Fixed income securities: U.S. government securities (2) 331.7 — 331.7 Non-U.S. government securities (3) 103.1 — 103.1 U.S. corporate bonds (3) 2,875.3 124.9 2,750.4 Non-U.S. corporate bonds (3) 540.7 — 540.7 Other fixed income (4) 388.0 — 388.0 Short-term investments (5) 168.7 168.7 — Benefit plan assets measured in the fair value hierarchy $ 4,664.5 $ 550.6 $ 4,113.9 Assets measured at NAV (6) 2,123.2 Total benefit plan assets $ 6,787.7 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2019 (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) $ 184.2 $ 183.5 $ 0.7 Non-U.S. equities (1) 6.5 6.5 — Fixed income securities: U.S. government securities (2) 598.2 — 598.2 Non-U.S. government securities (3) 125.6 0.2 125.4 U.S. corporate bonds (3) 2,156.0 137.6 2,018.4 Non-U.S. corporate bonds (3) 432.9 5.7 427.2 Other fixed income (4) 379.3 10.8 368.5 Short-term investments (5) 468.7 468.7 — Benefit plan assets measured in the fair value hierarchy $ 4,351.4 $ 813.0 $ 3,538.4 Assets measured at NAV (6) 2,054.8 Total benefit plan assets $ 6,406.2 (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 cleared swap 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) Investments that are measured at net asset value (“ NAV The following table summarizes assets measured at fair value based on NAV per share as a practical expedient as of September 30, 2020 and 2019 (in millions): Fair value Redemption Frequency Redemption Notice Period Unfunded Commitments September 30, 2020 Hedge funds (1) $ 39.2 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,416.9 Monthly Up to 60 days 228.9 Fixed income and fixed income related instruments (3) 667.1 Monthly Up to 10 days — $ 2,123.2 $ 228.9 September 30, 2019 Hedge funds (1) $ 42.9 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,188.6 Monthly Up to 60 days 113.1 Fixed income and fixed income related instruments (3) 823.3 Monthly Up to 10 days — $ 2,054.8 $ 113.1 (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. (2) Commingled fund investments are valued at the NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. (3) Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. 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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.00 % 4.84 % 3.34 % 5.64 % The following table shows the changes in benefit obligation, plan assets and funded status for the fiscal years ended September 30 (in millions): Postretirement Plans 2020 2019 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 $ 98.3 $ 75.7 $ 91.0 $ 55.5 Service cost 0.6 0.7 0.7 0.5 Interest cost 3.2 3.7 4.1 3.6 Amendments (0.1 ) 2.0 0.4 — Actuarial (gain) loss (3.1 ) (5.3 ) 1.6 22.2 Benefits paid (5.3 ) (2.9 ) (6.6 ) (2.9 ) Business combinations — — 7.1 — Foreign currency rate changes — (11.4 ) — (3.2 ) Benefit obligation at end of fiscal year $ 93.6 $ 62.5 $ 98.3 $ 75.7 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ — $ — $ — $ — Employer contributions 5.3 2.9 6.6 2.9 Benefits paid (5.3 ) (2.9 ) (6.6 ) (2.9 ) Fair value of plan assets at end of fiscal year $ — $ — $ — $ — Funded Status $ (93.6 ) $ (62.5 ) $ (98.3 ) $ (75.7 ) Amounts recognized in the consolidated balance sheet: Other current liabilities $ (8.0 ) $ (2.7 ) $ (8.9 ) $ (3.0 ) Postretirement benefit liabilities, net of current portion (85.6 ) (59.8 ) (89.4 ) (72.7 ) Under funded status at end of fiscal year $ (93.6 ) $ (62.5 ) $ (98.3 ) $ (75.7 ) 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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial (gain) loss $ (10.6 ) $ 13.0 $ (8.0 ) $ 18.8 Prior service (credit) cost (5.7 ) 1.2 (8.3 ) (0.9 ) Total accumulated other comprehensive (income) loss $ (16.3 ) $ 14.2 $ (16.3 ) $ 17.9 The pre-tax amounts recognized in other comprehensive loss (income), including noncontrolling interest, are as follows at September 30 (in millions): Postretirement Plans 2020 2019 2018 Net actuarial (gain) loss arising during period $ (8.4 ) $ 23.9 $ (9.7 ) Amortization and settlement recognition of net actuarial (loss) gain (0.1 ) 2.0 (0.3 ) Prior service cost (credit) arising during period 1.9 0.4 (1.5 ) Amortization or curtailment recognition of prior service credit 2.7 2.8 4.4 Net other comprehensive (income) loss recognized $ (3.9 ) $ 29.1 $ (7.1 ) 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 2020 2019 2018 Service cost $ 1.3 $ 1.2 $ 1.5 Interest cost 6.9 7.7 7.9 Amortization of net actuarial loss (gain) 0.1 (2.0 ) 0.3 Amortization of prior service credit (2.7 ) (2.8 ) (4.4 ) Curtailment gain — — (0.1 ) Net postretirement cost $ 5.6 $ 4.1 $ 5.2 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 5.57 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.42 % Year the rate reaches the ultimate trend rate 2038 Non-U.S. Plans Health care cost trend rate assumed for next year 5.25 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.25 % Year the rate reaches the ultimate trend rate 2020 As of September 30, 2020, the effect of a 1% change in the assumed health care cost trend rate would increase the APBO by approximately $10 million or decrease the APBO by approximately $8 million, and would increase the annual net periodic postretirement benefit cost for fiscal 2020 by $ 1 million or decrease the annual net periodic postretirement benefit cost for fiscal 2020 by approximately $ 1 million. Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Postretirement Plans 2020 2019 2018 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.34 % 5.64 % 4.50 % 6.61 % 4.09 % 6.51 % Rate of compensation increase N/A N/A N/A N/A N/A 7.37 % The estimated gains that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2021 are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Actuarial (gain) loss $ (1.3 ) $ 0.1 Prior service (credit) cost (2.5 ) 0.1 Total $ (3.8 ) $ 0.2 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 2021 $ 8.6 $ 2.7 Fiscal 2022 $ 7.6 $ 2.7 Fiscal 2023 $ 7.2 $ 2.8 Fiscal 2024 $ 6.9 $ 2.9 Fiscal 2025 $ 6.6 $ 3.0 Fiscal Years 2026 – 2030 $ 29.2 $ 16.7 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 (i) assets contributed to a MEPP by one employer are used to provide benefits to employees of all participating employers, (ii) 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 (iii) 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. Contributions to MEPPs are individually and in the aggregate not significant. 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 Central States, and recorded estimated withdrawal liabilities for each. We recorded an estimated withdrawal liability of $180.0 million for PIUMPF. The estimated withdrawal liability assumed payment over 20 years, discounted at a credit adjusted risk-free rate of 3.83%, and that PIUMPF’s demand related to the withdrawal would include both a payment for withdrawal liability and for our proportionate share of PIUMPF’s accumulated funding deficiency. The estimated withdrawal liability noted above excludes the potential impact of a future mass withdrawal of other employers from PIUMPF, which was not considered probable or reasonably estimable. In fiscal 2019 and 2020, we continued to refine the estimate of the withdrawal liability, the impact of which was not significant. 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. In September 2019, we received a demand from PIUMPF asserting that we owe $170.3 million on an undiscounted basis (approximately $0.7 million per month for the next 20 years) with respect to our withdrawal liability. The initial demand did not address any assertion of liability for PIUMPF’s accumulated funding deficiency. In October 2019, we received two additional demand letters from PIUMPF related to a subsidiary of ours asserting that we owe $2.3 million on an undiscounted basis to be paid over 20 years with respect to the subsidiary’s withdrawal liability and $2.0 million for its accumulated funding deficiency. We received an updated demand letter decreasing the accumulated funding deficiency demand from $2.0 million to $1.3 million in April 2020. In February 2020, we received a demand letter from PIUMPF asserting that we owe $51.2 million for our pro-rata share of PIUMPF’s accumulated funding deficiency, including interest. We are evaluating each of these demands and we expect to challenge the accumulated funding deficiency demands. We began making monthly payments for these withdrawal liabilities in fiscal 2020, excluding the accumulated funding deficiency demands. At September 30, 2020 and September 30, 2019, we had withdrawal liabilities recorded of $252.0 million and $237.2 million, respectively. The increase in the withdrawal liabilities in fiscal 2020 was primarily due to the decrease in interest rates. 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 and the trading price of our Common Stock. Approximately 56% of our employees are covered by CBAs in the U.S. and Canada, of which approximately 21% are covered by CBAs that expire within one year and another 15% are covered by CBAs that have expired. Defined Contribution Plans We have 401(k) and other defined contribution plans that cover certain of our U.S., Canadian and other non-U.S. salaried union and nonunion hourly employees, generally subject to an initial waiting period. The 401(k) and other defined contribution plans permit participants to make contributions by salary reduction pursuant to Section 401(k) of the Internal Revenue Code, or the taxing authority in the jurisdiction in which they operate. Due primarily to acquisitions, CBAs and other non-U.S. defined contribution programs, we have plans with varied terms. At September 30, 2020, our contributions may be up to 7.5% for U.S. salaried and non-union hourly employees, consisting of a match of up to 5% and an automatic employer contribution of 2.5%. Certain other employees who receive accruals under a defined benefit pension plan, certain employees covered by CBAs and non-U.S. defined contribution programs receive generally up to a 3.0% to 4.0% contribution to their 401(k) plan or defined contribution plan. During fiscal 2020, 2019 and 2018, we recorded expense of $150.1 million, $150.9 million and $113.7 million, respectively, related to employer contributions to the 401(k) plans and other defined contribution plans, including the automatic employer contribution. In connection with the WestRock Pandemic Action Plan, we began funding our matching contributions in Common Stock effective July 1, 2020 to the WestRock Company 401(k) Retirement Savings Plan. Supplemental Retirement Plans We have Supplemental Plans that are nonqualified deferred compensation plans. We intend to provide participants with an opportunity to supplement their retirement income through deferral of current compensation. Amounts deferred and payable under the Supplemental Plans are our unsecured obligations and rank equally with our other unsecured and unsubordinated indebtedness outstanding. Participants’ accounts are credited with investment gains and losses under the Supplemental Plans in accordance with the participant’s investment election or elections (or default election or elections) as in effect from time to time. At September 30, 2020, the Supplemental Plans had assets totaling $168.9 million that are recorded at market value, and liabilities of $176.1 million. The investment alternatives available under the Supplemental Plans are generally similar to investment alternatives available under 401(k) plans. The amount of expense we recorded for the current fiscal year and the preceding two fiscal years was not significant.

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 6. Income Taxes The components of (loss) income before income taxes are as follows (in millions): Year Ended September 30, 2020 2019 2018 United States $ (440.7 ) $ 891.6 $ 736.7 Foreign (81.9 ) 253.1 298.1 Income before income taxes $ (522.6 ) $ 1,144.7 $ 1,034.8 Impacts of the Tax Act On December 22, 2017, the U.S. enacted comprehensive tax legislation, commonly referred to as the Tax Act, which made broad and complex changes to the tax code. In conjunction with guidance set forth under SAB 118 pertaining to the Tax Act, we recorded provisional amounts both for the impact of remeasurement on its U.S. net deferred tax liabilities to the new U.S. statutory rate of 21% and for the mandatory transition tax on unrepatriated foreign earnings during fiscal 2018. During the first quarter of fiscal 2019, we completed the accounting for the income tax effect related to the Tax Act and made the following adjustments to the provisional amounts: (i) a $0.4 million tax expense from the true up and revaluation of deferred tax assets and liabilities to reflect the new tax rate and (ii) an additional $3.7 million tax expense, as a result of the refinement to the transition tax provisional liability. We have reclassified the transition tax liability for financial statement purposes to a reserve for uncertain tax position due to uncertainty in the realizability of certain foreign earnings and profits deficits. During the third quarter of fiscal 2020, we reduced our transition tax reserve by $16.4 million based on adjustments to expected post-1986 deferred foreign income as of the transition tax date. Beginning in fiscal 2019, we were subject to several provisions of the Tax Act, including computations under Global Intangible Low Taxed Income (“ GILTI FDII BEAT Interest Limitation As part of the enacted Tax Act, GILTI provisions were introduced that would impose a tax on foreign income in excess of a deemed return on tangible assets of foreign corporations. In January 2018, the FASB issued a question-and-answer document, stating that either accounting for deferred taxes related to GILTI inclusions or treating any taxes on GILTI inclusions as period costs are both acceptable methods subject to an accounting policy election. The GILTI provisions did not take effect for WestRock until fiscal 2019, and the Company has elected to treat any potential GILTI inclusions as a period cost during the year incurred. Income tax expense (benefit) consists of the following components (in millions): Year Ended September 30, 2020 2019 2018 Current income taxes: Federal $ 31.6 $ 134.7 $ 83.0 State 23.5 34.9 26.8 Foreign 66.8 69.5 86.6 Total current expense 121.9 239.1 196.4 Deferred income taxes: Federal 42.4 44.1 (1,108.6 ) State 6.2 6.1 53.2 Foreign (7.0 ) (12.5 ) (15.5 ) Total deferred expense (benefit) 41.6 37.7 (1,070.9 ) Total income tax expense (benefit) $ 163.5 $ 276.8 $ (874.5 ) The differences between the statutory federal income tax rate and our effective income tax rate are as follows: Year Ended September 30, 2020 (1) 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 24.5 % Foreign rate differential (1.1 ) 1.3 0.6 Adjustment and resolution of federal, state and foreign tax uncertainties 2.7 1.2 0.9 State taxes, net of federal benefit (1.3 ) 2.5 4.3 Tax Act (2) — — (109.1 ) Excess tax benefit related to stock compensation (0.5 ) (0.3 ) (0.8 ) Research and development and other tax credits, net of valuation allowances and reserves 3.7 (0.7 ) (0.5 ) Income attributable to noncontrolling interest 0.1 (0.1 ) (0.1 ) Domestic manufacturer’s deduction — — (1.8 ) Change in valuation allowance (4.1 ) 0.2 (1.8 ) Nondeductible transaction costs — 1.0 — Goodwill impairment (51.2 ) — — Nontaxable increased cash surrender value 1.3 (0.6 ) (0.8 ) Withholding taxes (0.7 ) 0.6 0.5 Brazilian net worth deduction 1.7 (0.9 ) (0.9 ) Other, net (2.9 ) (1.0 ) 0.5 Effective tax rate (31.3 )% 24.2 % (84.5 )% (1) The negative tax rate for fiscal year 2020 is the result of applying total income tax expense to the loss before income taxes. The signs within the table are consequently the opposite compared to prior year. (2) For the year ended September 30, 2018, 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, 2020 2019 Deferred income tax assets: Accruals and allowances $ 5.3 $ 10.7 Employee related accruals and allowances 121.3 125.1 Pension 60.5 96.8 State net operating loss carryforwards, net of federal benefit 67.0 57.6 State credit carryforwards, net of federal benefit 79.4 69.5 Federal and foreign net operating loss carryforwards 188.3 173.5 Restricted stock and options 33.7 39.3 Lease liabilities 179.1 — Other 52.8 52.8 Total 787.4 625.3 Deferred income tax liabilities: Property, plant and equipment 1,885.5 1,840.5 Deductible intangibles and goodwill 841.5 914.7 Inventory reserves 216.2 188.3 Deferred gain 272.2 275.2 Basis difference in joint ventures 33.8 33.1 Right-of-use assets 163.8 — Total 3,413.0 3,251.8 Valuation allowances 257.5 218.0 Net deferred income tax liability $ 2,883.1 $ 2,844.5 Deferred taxes are recorded as follows in the consolidated balance sheet (in millions): September 30, 2020 2019 Long-term deferred tax asset (1) $ 33.8 $ 33.5 Long-term deferred tax liability 2,916.9 2,878.0 Net deferred income tax liability $ 2,883.1 $ 2,844.5 (1) The long-term deferred tax asset is presented in Other assets on the consolidated balance sheets. At September 30, 2020 and September 30, 2019, we had gross U.S. federal net operating losses of approximately $2.6 million and $4.0 million, respectively. These loss carryforwards generally expire between fiscal 2031 and 2038. At September 30, 2020 and September 30, 2019, we had gross state and local net operating losses, of approximately $1,795 million and $1,638 million, respectively. These loss carryforwards generally expire between fiscal 2022 and 2040. The tax effected values of these net operating losses are $67.0 million and $57.6 million at September 30, 2020 and 2019, respectively, exclusive of valuation allowances of $12.7 million and $10.2 million at September 30, 2020 and 2019, respectively. At September 30, 2020 and September 30, 2019, gross net operating losses for foreign reporting purposes of approximately $765.1 million and $663.2 million, respectively, were available for carryforward. A majority of these loss carryforwards generally expire between fiscal 2022 and 2040, while a portion have an indefinite carryforward. The tax effected values of these net operating losses are $187.7 million and $172.5 million at September 30, 2020 and 2019, respectively, exclusive of valuation allowances of $165.9 million and $144.1 million at September 30, 2020 and 2019, respectively. At September 30, 2020 and 2019, we had state tax credit carryforwards of $79.4 million and $69.5 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 $71.9 million and $56.8 million at September 30, 2020 and 2019, 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 2020, 2019 and 2018 (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 218.0 $ 229.4 $ 219.1 Increases 46.2 25.4 50.8 Allowances related to purchase accounting (1) — 0.8 0.1 Reductions (6.7 ) (37.6 ) (40.6 ) Balance at end of fiscal year $ 257.5 $ 218.0 $ 229.4 (1) Amounts in fiscal 2019 relate to the KapStone Acquisition. Amounts in fiscal 2018 relate to the MPS 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, 2020, we estimate our outside basis difference in foreign subsidiaries that are considered indefinitely reinvested to be approximately $1.7 billion. The components of the outside basis difference are comprised of purchase accounting adjustments (i.e. from mergers and acquisitions), 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, 2020, 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): 2020 2019 2018 Balance at beginning of fiscal year $ 224.3 $ 127.1 $ 148.9 Additions related to purchase accounting (1) — 1.0 3.4 Additions for tax positions taken in current year (2) 5.0 103.8 3.1 Additions for tax positions taken in prior fiscal years 11.7 1.8 18.0 Reductions for tax positions taken in prior fiscal years (2) (16.7 ) (0.5 ) (5.3 ) Reductions due to settlement (3) — (4.0 ) (29.4 ) Reductions for currency translation adjustments (8.8 ) (1.7 ) (9.6 ) Reductions as a result of a lapse of the applicable statute of limitations (8.8 ) (3.2 ) (2.0 ) Balance at end of fiscal year $ 206.7 $ 224.3 $ 127.1 (1) (2) (3) Amounts in fiscal 2019 relate to the settlements of state and foreign audit examinations. 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 there was a reserve. As of September 30, 2020 and 2019, the total amount of unrecognized tax benefits was approximately $206.7 million and $224.3 million, respectively, exclusive of interest and penalties. Of these balances, as of September 30, 2020 and 2019, if we were to prevail on all unrecognized tax benefits recorded, approximately $189.5 million and $207.5 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. Resolution of the uncertain tax positions could have a material adverse effect on our cash flows or materially benefit our results of operations in future periods depending upon their ultimate resolution. See “ Note 18. Commitments and Contingencies — Brazil Tax Liability ”. We recognize estimated interest and penalties related to unrecognized tax benefits in income tax expense in the consolidated statements of income. As of September 30, 2020, we had liabilities of $72.4 million related to estimated interest and penalties for unrecognized tax benefits. As of September 30, 2019, we had liabilities of $80.0 million, related to estimated interest and penalties for unrecognized tax benefits. Our results of operations for the fiscal year ended September 30, 2020, 2019 and 2018 include expense of $6.6 million, $9.7 million and $5.8 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, 2020, it is reasonably possible that our unrecognized tax benefits will decrease by up to $21.9 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 income tax examinations by tax authorities for years prior to fiscal 2017 and state and local income tax examinations by tax authorities for years prior to fiscal 2010. We are no longer subject to non-U.S. income tax examinations by tax authorities for years prior to fiscal 2009, except for Brazil for which we are not subject to tax examinations for years prior to 2006. 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, 2020
Segment Reporting [Abstract]
Segment Information	Note 7. Segment Information We report our financial results of operations in the following three reportable segments: Corrugated Packaging, which consists of our containerboard mills, corrugated packaging and distribution operations, as well as our merchandising displays and recycling procurement operations; Consumer Packaging, which consists of our consumer mills, food and beverage and partition operations; and Land and Development, which previously sold real estate, primarily in the Charleston, SC region. With the completion of the monetization, this segment will no longer exist. 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 selected operating data 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, 2020 2019 2018 Foreign net sales to unaffiliated customers $ 3,105.6 $ 3,332.4 $ 3,236.7 Foreign segment income $ 298.2 $ 392.3 $ 360.7 Foreign long-lived assets $ 1,390.6 $ 1,466.4 $ 1,400.2 Foreign operations as a percent of consolidated operations: Foreign net sales to unaffiliated customers 17.7 % 18.2 % 19.9 % Foreign segment income 21.9 % 21.9 % 21.1 % Foreign long-lived assets 12.9 % 13.1 % 15.4 % 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, 2020 2019 2018 Net sales (aggregate): Corrugated Packaging $ 11,419.2 $ 11,816.7 $ 9,693.0 Consumer Packaging 6,333.0 6,606.0 6,617.5 Land and Development 18.9 23.4 142.4 Total $ 17,771.1 $ 18,446.1 $ 16,452.9 Less net sales (intersegment): Corrugated Packaging $ 71.0 $ 75.3 $ 87.3 Consumer Packaging 121.3 81.8 80.5 Total $ 192.3 $ 157.1 $ 167.8 Net sales (unaffiliated customers): Corrugated Packaging $ 11,348.2 $ 11,741.4 $ 9,605.7 Consumer Packaging 6,211.7 6,524.2 6,537.0 Land and Development 18.9 23.4 142.4 Total $ 17,578.8 $ 18,289.0 $ 16,285.1 Segment income: Corrugated Packaging $ 1,037.7 $ 1,399.6 $ 1,240.0 Consumer Packaging 323.7 388.1 445.1 Land and Development 1.4 2.5 22.5 Segment income 1,362.8 1,790.2 1,707.6 Gain on sale of certain closed facilities 15.6 52.6 — Multiemployer pension withdrawal income (expense) 1.1 6.3 (184.2 ) Land and Development impairments — (13.0 ) (31.9 ) Restructuring and other costs (112.7 ) (173.7 ) (105.4 ) Goodwill impairment (1,333.2 ) — — Non-allocated expenses (70.7 ) (83.7 ) (70.1 ) Interest expense, net (393.5 ) (431.3 ) (293.8 ) Loss on extinguishment of debt (1.5 ) (5.1 ) (0.1 ) Other income, net 9.5 2.4 12.7 (Loss) income before income taxes $ (522.6 ) $ 1,144.7 $ 1,034.8 Years Ended September 30, 2020 2019 2018 Depreciation and amortization: Corrugated Packaging $ 951.4 $ 950.6 $ 700.5 Consumer Packaging 529.5 552.1 546.5 Land and Development — — 0.7 Corporate 6.1 8.5 4.5 Total $ 1,487.0 $ 1,511.2 $ 1,252.2 In October 2018, our containerboard and pulp mill located in Panama City, FL sustained extensive damage from Hurricane Michael. In fiscal 2019, we received $180.0 million of Hurricane Michael-related insurance proceeds that were recorded as a reduction of cost of goods sold in our Corrugated Packaging segment. The insurance proceeds consisted of $55.3 million for business interruption recoveries and $124.7 million for direct costs and property damage. Our consolidated statements of cash flow in fiscal 2019 included $154.5 million in net cash provided by operating activities and $25.5 million in net cash used for investing activities. In fiscal 2020, we received the remaining Hurricane Michael-related insurance proceeds of $32.3 million, that were recorded as a reduction of cost of goods sold in our Corrugated Packaging segment. The insurance proceeds consisted of $11.7 million of business interruption recoveries and $20.6 million for direct costs and property damage. Our consolidated statement of cash flows for fiscal 2020 included $30.9 million in net cash provided by operating activities and $1.4 million of cash proceeds included in net cash used for investing activities related to Hurricane Michael. In addition, we had other minor amounts for various claims that were recorded as a reduction of cost of goods sold across our segments. Corrugated Packaging segment income in fiscal 2019 and 2018 was reduced by $24.7 million and $1.0 million, respectively, of expense for inventory stepped-up in purchase accounting, net of related LIFO impact. The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2020 2019 2018 Identifiable assets: Corrugated Packaging $ 16,507.0 $ 16,681.1 $ 11,069.6 Consumer Packaging 9,584.9 11,038.7 11,511.1 Land and Development — 28.3 49.1 Assets held for sale 7.0 25.8 59.5 Corporate 2,680.8 2,382.8 2,671.2 Total $ 28,779.7 $ 30,156.7 $ 25,360.5 Goodwill: Corrugated Packaging $ 3,673.5 $ 3,695.0 $ 1,966.7 Consumer Packaging 2,288.7 3,590.6 3,610.9 Total $ 5,962.2 $ 7,285.6 $ 5,577.6 Intangibles, net: Corrugated Packaging $ 1,423.0 $ 1,655.1 $ 506.2 Consumer Packaging 2,244.2 2,404.4 2,615.8 Total $ 3,667.2 $ 4,059.5 $ 3,122.0 Capital expenditures: Corrugated Packaging $ 731.1 $ 961.4 $ 657.3 Consumer Packaging 217.1 365.9 308.3 Corporate 29.9 41.8 34.3 Total $ 978.1 $ 1,369.1 $ 999.9 Equity method investments: Corrugated Packaging $ 414.3 $ 457.1 $ 455.6 Consumer Packaging 14.9 11.6 1.8 Corporate 0.4 0.4 0.4 Total $ 429.6 $ 469.1 $ 457.8 The Corrugated Packaging segment’s equity method investments primarily relate to the Grupo Gondi investment. Equity method investments are included in the balance sheet in other assets. The investment in Grupo Gondi that in fiscal 2020 and 2019 exceeds our proportionate share of the underlying equity in net assets by approximately $101.7 million and $121.4 million, respectively. Approximately $41.9 million and $53.1 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. The Gondi investment is denominated in Mexican Pesos. The changes in the carrying amount of goodwill for the fiscal years ended September 30, 2020, 2019 and 2018 are as follows (in millions): Corrugated Packaging Consumer Packaging Total Balance as of October 1, 2017 Goodwill $ 1,941.6 $ 3,629.5 $ 5,571.1 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 1,941.5 3,586.8 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 1,966.8 3,653.6 5,620.4 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 1,966.7 3,610.9 5,577.6 Goodwill acquired 1,746.4 3.8 1,750.2 Purchase price allocation adjustments 0.9 (1.4 ) (0.5 ) Translation and other adjustments (19.0 ) (22.7 ) (41.7 ) Balance as of September 30, 2019 Goodwill 3,695.1 3,633.3 7,328.4 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 3,695.0 3,590.6 7,285.6 Goodwill impairment — (1,333.2 ) (1,333.2 ) Goodwill disposed of — (0.3 ) (0.3 ) Purchase price allocation adjustments 14.3 (0.6 ) 13.7 Translation adjustments (35.8 ) 32.2 (3.6 ) Balance as of September 30, 2020 Goodwill 3,673.6 3,664.6 7,338.2 Accumulated impairment losses (0.1 ) (1,375.9 ) (1,376.0 ) $ 3,673.5 $ 2,288.7 $ 5,962.2 See “ Note 1. Description of Business and Summary of Significant Accounting Policies — Goodwill and Long-Lived Assets pre-tax non-cash goodwill impairment of our Consumer Packaging reporting unit. The goodwill acquired in fiscal 2019 primarily related to the KapStone Acquisition in the Corrugated Packaging segment. 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 acquisition of MPS and the acquisition of Hanna Group Pty Ltd. The goodwill disposed of in the Corrugated Packaging segment in fiscal 2018 related to the sale of our solid waste management brokerage services business. See “ Note 3. Acquisitions and Investments

Interest Expense, Net

Interest Expense, Net	12 Months Ended
	Sep. 30, 2020
Interest Income Expense Net [Abstract]
Interest Expense, Net	Note 8. Interest Expense, Net The components of interest expense, net is as follows (in millions): Years Ended September 30, 2020 2019 2018 Interest expense $ (465.5 ) $ (489.4 ) $ (352.8 ) Interest income 72.0 58.1 59.0 Interest expense, net $ (393.5 ) $ (431.3 ) $ (293.8 )

Inventories

Inventories	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventories	Note 9. Inventories Inventories are as follows (in millions): September 30, 2020 2019 Finished goods and work in process $ 844.2 $ 938.9 Raw materials 772.7 818.8 Supplies and spare parts 500.3 479.7 Inventories at FIFO cost 2,117.2 2,237.4 LIFO reserve (93.8 ) (129.9 ) Net inventories $ 2,023.4 $ 2,107.5 It is impracticable to segregate the LIFO reserve between raw materials, finished goods and work in process. In fiscal 2020, 2019 and 2018, 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. Alternatively, they have higher costs prevailing in prior years which increases costs of goods sold. The impact of the liquidations in fiscal 2020, 2019 and 2018 was not significant.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Sep. 30, 2020
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, 2020 2019 Property, plant and equipment at cost: Land and buildings $ 2,524.7 $ 2,442.3 Machinery and equipment 15,147.3 14,743.6 Forestlands and mineral rights 110.8 144.0 Transportation equipment 29.1 31.2 Leasehold improvements 103.6 100.2 17,915.5 17,461.3 Less: accumulated depreciation, depletion and amortization (7,136.6 ) (6,271.8 ) Property, plant and equipment, net $ 10,778.9 $ 11,189.5 Depreciation expense for fiscal 2020, 2019 and 2018 was $1,054.9 million, $1,074.6 million and $923.8 million, respectively.

Other Intangible Assets

Other Intangible Assets	12 Months Ended
	Sep. 30, 2020
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, are as follows (in millions, except weighted avg. life): September 30, 2020 2019 Weighted Avg. Life (in years) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships 15.5 $ 5,418.1 $ (1,841.2 ) $ 5,395.5 $ (1,452.1 ) Trademarks and tradenames 21.6 130.5 (65.7 ) 129.9 (55.3 ) Favorable contracts 7.2 44.0 (41.6 ) 57.0 (42.6 ) Technology and patents 11.4 37.5 (21.6 ) 39.2 (21.2 ) License costs 8.0 26.5 (22.8 ) 25.7 (20.5 ) Non-compete agreements 2.0 3.4 (3.3 ) 3.4 (2.9 ) Other 29.5 3.7 (0.3 ) 3.6 (0.2 ) Total 15.5 $ 5,663.7 $ (1,996.5 ) $ 5,654.3 $ (1,594.8 ) Estimated intangible asset amortization expense for the succeeding five fiscal years is as follows (in millions): Fiscal 2021 $ 356.8 Fiscal 2022 $ 349.3 Fiscal 2023 $ 343.1 Fiscal 2024 $ 322.6 Fiscal 2025 $ 308.0 Intangible amortization expense was $405.4 million, $408.0 million and $300.8 million during fiscal 2020, 2019 and 2018, respectively. We had other intangible amortization expense, primarily for packaging equipment leased to customers of $26.7 million, $28.6 million and $27.6 million during fiscal 2020, 2019 and 2018, respectively.

Fair Value

Fair Value	12 Months Ended
	Sep. 30, 2020
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 5. 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 On September 25, 2018 we entered into a $550.0 million agreement (the “ A/R Sales Agreement ”) Transfers and Servicing Note 13. Debt In connection with the September 25, 2018 termination of the prior agreement and execution of the A/R Sales Agreement, there was a non-cash transaction of $424.8 million representing the repurchase of receivables previously sold to the financial institution under the prior agreement and the sale of the same receivables to the financial institution under the A/R Sales Agreement. The following table represents a summary of the activity under the A/R Sales Agreement for fiscal 2020 and 2019 (in millions): 2020 2019 Receivable from financial institution at beginning of fiscal year $ — $ — Receivables sold to the financial institution and derecognized 2,446.2 2,051.6 Receivables collected by financial institution (2,449.4 ) (1,971.1 ) Cash proceeds from financial institution 3.2 (80.5 ) Receivable from financial institution at September 30, $ — $ — Receivables sold under our A/R Sales Agreement were approximately $589.4 million and $592.6 million as of September 30, 2020 and September 30, 2019, respectively. 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. While the expense recorded in connection with the sale of receivables may vary based on current rates and levels of receivables sold, the expense recorded in connection with the sale of receivables was $12.7 million, $17.3 million and $11.2 million in fiscal 2020, 2019 and 2018, respectively, and is recorded in “other income, net” in the consolidated statements of operations. 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. Fair Value of Nonfinancial Assets and Nonfinancial Liabilities As discussed in “ Note 1. Description of Business and Summary of Significant Accounting Policies Note 1. Description of Business and Summary of Significant Accounting Policies — Goodwill and Long-Lived Assets pre-tax non-cash goodwill impairment of our Consumer Packaging reporting unit. Note 4. Restructuring and Other Costs following the termination of a third party leasing relationship, projects in connection with the accelerated monetization strategy in our Land and Development segment where the projected sales proceeds were less than the carrying value.

Debt

Debt	12 Months Ended
	Sep. 30, 2020
Debt [Abstract]
Debt	Note 1 3. Debt The public bonds issued by WRKCo, RKT The following were individual components of debt (in millions, except percentages): September 30, 2020 September 30, 2019 Carrying Value Weighted Avg Interest Rate Carrying Value Weighted Avg Interest Rate Public bonds due fiscal 2020 to 2022 $ 399.3 5.0 % $ 507.8 4.9 % Public bonds due fiscal 2023 to 2028 3,773.6 4.0 % 3,769.1 4.0 % Public bonds due fiscal 2029 to 2033 2,778.9 4.5 % 2,197.6 4.9 % Public bonds due fiscal 2037 to 2047 178.6 6.2 % 179.0 6.2 % Term loan facilities 1,547.6 1.9 % 2,295.5 3.3 % Revolving credit and swing facilities 250.0 1.1 % 396.0 2.9 % Commercial paper — N/A 339.2 2.4 % Finance lease obligations 274.8 4.0 % 185.8 4.3 % Vendor financing and commercial card programs 89.8 N/A 123.2 N/A International and other debt 138.0 3.1 % 70.2 6.6 % Total debt 9,430.6 3.8 % 10,063.4 4.0 % Less: current portion of debt 222.9 561.1 Long-term debt due after one year $ 9,207.7 $ 9,502.3 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, 2020. The increase in finance lease obligations during fiscal 2020 was primarily the result of our adoption on October 1, 2019 of the leasing guidance codified in ASC 842 that caused us to recharacterize a short-term and long-term liability for two chip mills to a $100.3 million finance lease obligation. The carrying value of our debt includes the fair value step-up of debt acquired in mergers and acquisitions, and the weighted average interest rate includes the fair value step up. At September 30, 2020, excluding the step-up, the weighted average interest rate on total debt was 3.9%. At September 30, 2020, the unamortized fair market value step-up was $208.9 million, which will be amortized over a weighted average remaining life of 11.5 years. At September 30, 2020, we had $62.9 million of outstanding letters of credit not drawn upon. At September 30, 2020, we had approximately $3.6 billion of availability under long-term committed credit facilities and cash and cash equivalents. 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 $10.4 billion and $10.6 billion as of September 30, 2020 and September 30, 2019, 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 approximate their carrying amount, as the variable interest rates reprice frequently at observable current market rates. During fiscal 2020, 2019 and 2018, amortization of debt issuance costs charged to interest expense were $8.2 million, $7.8 million and $6.3 million, respectively. Public Bonds / Notes Issued At September 30, 2020 and September 30, 2019, the face value of our public bond obligations outstanding were $7.0 billion and $6.5 billion, respectively. On June 1, 2020, WRKCo issued $600.0 million aggregate principal amount of its 3.00% Senior Notes due 2033 in a registered offering pursuant to the Company’s automatic shelf registration statement on Form S-3 under the Securities Act of 1933, as amended, (the “ Securities Act Parent Guarantor Subsidiaries On May 16, 2019, WRKCo issued $500.0 million aggregate principal amount of its 3.90% Senior Notes due 2028 (the “ June 2028 Notes 2032 Notes May 2019 Notes On December 3, 2018, WRKCo issued $750.0 million aggregate principal amount of its 4.65% Senior Notes due 2026 (the “ 2026 Notes 2029 Notes December 2018 Notes 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 “ March 2018 Notes Exchanged Notes During fiscal 2019, we conducted offers to exchange WRKCo’s $500.0 million aggregate principal amount of 3.00% Senior Notes due 2024 (the “ 2024 Notes 2025 Notes 2027 Notes 2028 Notes Revolving Credit Facility On November 21, 2019, we amended our $2.0 billion unsecured revolving credit facility entered into on July 1, 2015 to, among other things, increase the committed principal to $2.3 billion, increase the maximum permitted Debt to Capitalization Ratio (as defined in the credit agreement) from 0.60:1:00 to 0.65:1.00 and extend its maturity date to November 21, 2024 (“ Revolving Credit Facility At our option, loans issued under the Revolving Credit Facility will bear interest at either LIBOR or an alternate base rate, in each case plus an applicable interest rate margin. Loans will initially bear interest at LIBOR plus 1.125% per annum, in the case of LIBOR borrowings, or at the alternate base rate plus 0.125% per annum, in the alternative, and thereafter the interest rate will fluctuate between LIBOR plus 1.00% per annum and LIBOR plus 1.75% per annum (or between the alternate base rate plus 0.00% per annum and the alternate base rate plus 0.75% per annum), based upon our corporate credit ratings or the leverage ratio (as defined in the Credit Agreement) (whichever yields a lower applicable interest rate margin) at such time. In addition, we will be required to pay fees that will fluctuate between 0.125% per annum to 0.30% per annum on the unused amount of the revolving credit facility, based upon our corporate credit ratings or the leverage ratio (whichever yields a lower fee) at such time. Loans under the Revolving Credit Facility may be prepaid at any time without premium. Bank of America Term Loan On June 7, 2019, we entered into a $300.0 million credit agreement providing for a 5-year unsecured term loan with Bank of America, N.A., as administrative agent. The facility is scheduled to mature on June 7, 2024. The proceeds from the facility were used to prepay a portion of the then outstanding amount under our commercial paper program. The applicable interest rate margin was initially 0.825% to 1.750% per annum for LIBOR rate loans and 0.000% to 0.750% per annum for alternate base rate loans, in each case depending on the Leverage Ratio (as defined in the credit agreement) or our corporate credit ratings, whichever yields a lower applicable interest rate margin, at such time. At September 30, 2020 and September 30, 2019, the carrying value of this facility was $300.0 million and $300.0 million outstanding, respectively. Farm Loan Credit Facility On September 27, 2019, one of our wholly-owned subsidiaries, WestRock Southeast LLC, entered into a credit agreement (the “ Farm Loan Credit Agreement Farm Loan Credit Facility European Revolving Credit Facility 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. This facility provides for a 3-year unsecured U.S. dollar, Euro and British Pound denominated borrowing of not more than 500.0 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 facility was subsequently renewed on October 29, 2018 and October 25, 2019, each for 364 days 30 Receivables Securitization Facility On May 2, 2019, we amended our $700.0 million receivables securitization agreement (the “ Receivables Securitization Facility Commercial Paper Program On December 7, 2018, we established a new unsecured commercial paper program with WRKCo as the issuer. Under the new program, 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 program has no expiration date and can be terminated by either the agent or us with not less than 30 days’ notice. Our Revolving Credit Facility is intended to backstop the commercial paper program. Amounts available under the program may be borrowed, repaid and re-borrowed from time to time. The net proceeds from issuances of notes under the program were initially used to repay amounts outstanding under the KapStone securitization facility that was assumed in the KapStone Acquisition and subsequently terminated, and have been, and are expected to continue to be, used for general corporate purposes. The new program replaced our then-existing program. At September 30, 2020, there was no amount outstanding. At September 30, 2019, there was $339.2 million outstanding and the average borrowing rate was 2.39%. As of September 30, 2019, $250.0 million of the total amount outstanding was classified as long-term debt. Delayed Draw Credit Facilities On March 7, 2018, we entered into a credit agreement with Wells Fargo as administrative agent to provide for $3.8 billion of senior unsecured term loans, consisting of a 364-day $300.0 million term loan, a 3-year $1.75 billion term loan and a 5-year $1.75 billion term loan (collectively, the “ Delayed Draw Credit Facilities 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. On February 26, 2019, we amended the Delayed Draw Credit Agreement. The applicable interest rate margin for the 5-year term loan is now 1.000% to 1.950% for LIBOR rate loans and 0.000% to 0.950% for alternate base rate loans. At September 30, 2019, there were no amounts outstanding under the 364-day and 3-year term loans, and the carrying value of the 5-year term loan was $1,396.9 million. In fiscal 2020, we prepaid $750.0 million of our 5-year term loan using cash and cash equivalents and proceeds from the issuance of commercial paper. At September 30, 2020, the carrying value of the 5-year term loan was $648.9 million. Brazil Delayed Draw Credit Facilities On April 10, 2019, we entered into a credit agreement to provide for R$750.0 million of senior unsecured term loans with an incremental R$250.0 million accordion feature (the “ Brazil Delayed Draw Credit Facilities Aggregate Maturities of Debt As of September 30, 2020, the aggregate maturities of debt, excluding finance lease obligations, for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2021 $ 214.2 Fiscal 2022 438.7 Fiscal 2023 639.1 Fiscal 2024 1,386.8 Fiscal 2025 600.0 Thereafter 5,729.1 Fair value of debt step-up, deferred financing costs and unamortized bond discounts 147.9 Total $ 9,155.8 See “ Note 15. Leases ” of the Notes to Consolidated Financial Statements for the aggregate maturities of finance lease obligations for the succeeding five fiscal years and thereafter.

Selected Condensed Consolidatin

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors	12 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors	Note 14. The 2024 Notes, the 2025 Notes, the 2026 Notes, the 2027 Notes, the 2028 Notes, the June 2028 Notes, the 2029 Notes, the 2032 Notes and the June 2033 Notes (collectively, the “ Notes Issuer Parent Subsidiaries. Accordingly, each series of the Notes is fully and unconditionally guaranteed on a joint and several basis by Parent and the Guarantor Subsidiaries. In accordance with GAAP, we retrospectively account for changes in our legal structure that constitute transfers of businesses between issuers, guarantors and non-guarantors. As such, our prior period financials may vary from those previously reported. The information in the tables reflect such revisions, as well as revisions to correct immaterial errors in the prior presentation of our financial statements. In accordance with Rule 3-10 of Regulation S-X, the following tables present condensed consolidating financial data of the Parent, the Issuer, the Guarantor Subsidiaries, the non-guarantor subsidiaries and eliminations. Such financial data include Condensed Consolidating Balance Sheet data as of September 30, 2020 and 2019 and the related Condensed Consolidating Statement of Income and Cash Flow data for each of the three years in the period ended September 30, 2020. CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,430.9 $ 17,740.7 $ (2,592.8 ) $ 17,578.8 Cost of goods sold — — 1,916.7 15,026.1 (2,561.2 ) 14,381.6 Gross profit — — 514.2 2,714.6 (31.6 ) 3,197.2 Selling, general and administrative, excluding intangible amortization — 2.8 101.2 1,520.4 — 1,624.4 Selling, general and administrative intangible amortization — — 99.5 301.0 — 400.5 Gain on disposal of assets — — (0.1 ) (16.2 ) — (16.3 ) Multiemployer pension withdrawal (income) expense — — (1.9 ) 0.8 — (1.1 ) Restructuring and other costs — 4.6 — 108.1 — 112.7 Goodwill impairment — — 746.9 586.3 — 1,333.2 Operating (loss) profit — (7.4 ) (431.4 ) 214.2 (31.6 ) (256.2 ) Interest expense, net — (250.1 ) (137.9 ) (5.5 ) — (393.5 ) Intercompany interest (expense) income, net — (10.2 ) (80.7 ) 59.3 31.6 — Loss on extinguishment of debt — (1.4 ) — (0.1 ) — (1.5 ) Pension and other postretirement non-service (expense) income — — (6.9 ) 110.2 — 103.3 Other income (expense), net 0.1 0.2 (82.6 ) 91.8 — 9.5 Equity in income of unconsolidated entities — — — 15.8 — 15.8 Equity in (loss) income of consolidated entities (691.0 ) (343.2 ) 228.6 — 805.6 — (Loss) income before income taxes (690.9 ) (612.1 ) (510.9 ) 485.7 805.6 (522.6 ) Income tax benefit (expense) — 77.7 11.4 (252.6 ) — (163.5 ) Consolidated net (loss) income (690.9 ) (534.4 ) (499.5 ) 233.1 805.6 (686.1 ) Less: Net income attributable to noncontrolling interests — — — (4.8 ) — (4.8 ) Net (loss) income attributable to common stockholders $ (690.9 ) $ (534.4 ) $ (499.5 ) $ 228.3 $ 805.6 $ (690.9 ) Comprehensive (loss) income attributable to common stockholders $ (868.2 ) $ (711.0 ) $ (677.1 ) $ 51.4 $ 1,336.7 $ (868.2 ) CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,543.8 $ 18,364.4 $ (2,619.2 ) $ 18,289.0 Cost of goods sold — — 2,026.0 15,114.2 (2,600.2 ) 14,540.0 Gross profit — — 517.8 3,250.2 (19.0 ) 3,749.0 Selling, general and administrative, excluding intangible amortization — (0.9 ) 120.0 1,596.1 — 1,715.2 Selling, general and administrative intangible amortization — — 104.4 295.8 — 400.2 Loss (gain) on disposal of assets — — 0.1 (41.3 ) — (41.2 ) Multiemployer pension withdrawal income — (0.2 ) (0.3 ) (5.8 ) — (6.3 ) Land and Development impairments — — — 13.0 — 13.0 Restructuring and other costs — 7.6 0.3 165.8 — 173.7 Operating profit (loss) — (6.5 ) 293.3 1,226.6 (19.0 ) 1,494.4 Interest expense, net — (246.8 ) (163.4 ) (21.1 ) — (431.3 ) Intercompany interest (expense) income, net — (3.2 ) (115.3 ) 99.5 19.0 — Loss on extinguishment of debt — (3.0 ) (1.9 ) (0.2 ) — (5.1 ) Pension and other postretirement non-service (expense) income — — (6.5 ) 80.7 — 74.2 Other (expense) income, net — (5.1 ) 3.4 4.1 — 2.4 Equity in income of unconsolidated entities — — — 10.1 — 10.1 Equity in income of consolidated entities 862.9 1,157.3 736.5 — (2,756.7 ) — Income before income taxes 862.9 892.7 746.1 1,399.7 (2,756.7 ) 1,144.7 Income tax benefit (expense) — 67.9 7.2 (351.9 ) — (276.8 ) Consolidated net income 862.9 960.6 753.3 1,047.8 (2,756.7 ) 867.9 Less: Net income attributable to noncontrolling interests — — — (5.0 ) — (5.0 ) Net income attributable to common stockholders $ 862.9 $ 960.6 $ 753.3 $ 1,042.8 $ (2,756.7 ) $ 862.9 Comprehensive income attributable to common stockholders $ 489.0 $ 588.0 $ 389.4 $ 682.4 $ (1,659.8 ) $ 489.0 CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,593.0 $ 16,345.4 $ (2,653.3 ) $ 16,285.1 Cost of goods sold — — 2,004.2 13,572.2 (2,653.3 ) 12,923.1 Gross profit — — 588.8 2,773.2 — 3,362.0 Selling, general and administrative, excluding intangible amortization — 1.5 94.1 1,451.0 — 1,546.6 Selling, general and administrative intangible amortization — — 104.2 192.4 — 296.6 Loss on disposal of assets — — 0.2 9.9 — 10.1 Multiemployer pension withdrawals — 6.5 12.5 165.2 — 184.2 Land and Development impairments — — — 31.9 — 31.9 Restructuring and other costs — 8.7 5.6 91.1 — 105.4 Operating profit (loss) — (16.7 ) 372.2 831.7 — 1,187.2 Interest expense, net (12.5 ) (76.9 ) (173.5 ) (30.9 ) — (293.8 ) Intercompany interest income (expense), net — 28.1 (87.6 ) 59.5 — — (Loss) gain on extinguishment of debt (0.2 ) (1.4 ) 1.9 (0.4 ) — (0.1 ) Pension and other postretirement non-service (expense) income — — (6.9 ) 102.2 — 95.3 Other income (expense), net — 0.7 (22.5 ) 34.5 — 12.7 Equity in income of unconsolidated entities — — 7.5 26.0 — 33.5 Equity in income of consolidated entities — 1,962.0 1,343.8 — (3,305.8 ) — Income (loss) before income taxes (12.7 ) 1,895.8 1,434.9 1,022.6 (3,305.8 ) 1,034.8 Income tax benefit 3.1 19.9 131.8 719.7 — 874.5 Consolidated net income (loss) (9.6 ) 1,915.7 1,566.7 1,742.3 (3,305.8 ) 1,909.3 Less: Net income attributable to noncontrolling interests — — — (3.2 ) — (3.2 ) Net income (loss) attributable to common stockholders $ (9.6 ) $ 1,915.7 $ 1,566.7 $ 1,739.1 $ (3,305.8 ) $ 1,906.1 Comprehensive income (loss) attributable to common stockholders $ (9.6 ) $ 1,677.7 $ 1,351.4 $ 1,498.6 $ (2,850.0 ) $ 1,668.1 CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total ASSETS Current assets: Cash and cash equivalents $ — $ — $ 105.7 $ 145.4 $ — $ 251.1 Accounts receivable — — 41.6 2,152.0 (50.9 ) 2,142.7 Inventories — — 175.3 1,848.1 — 2,023.4 Other current assets 0.5 — 11.6 508.4 — 520.5 Intercompany receivables — 3.0 1.5 1,798.6 (1,803.1 ) — Assets held for sale — — — 7.0 — 7.0 Total current assets 0.5 3.0 335.7 6,459.5 (1,854.0 ) 4,944.7 Property, plant and equipment, net — — 15.2 10,763.7 — 10,778.9 Goodwill — — 411.7 5,550.5 — 5,962.2 Intangibles, net — — 1,385.5 2,281.7 — 3,667.2 Restricted assets held by special purpose entities — — — 1,267.5 — 1,267.5 Prepaid pension asset — — — 368.7 — 368.7 Intercompany notes receivable — 168.8 141.1 2,821.3 (3,131.2 ) — Investments in consolidated subsidiaries 11,070.4 17,829.4 19,685.2 — (48,585.0 ) — Other assets — 63.6 220.8 1,565.5 (59.4 ) 1,790.5 Total assets $ 11,070.9 $ 18,064.8 $ 22,195.2 $ 31,078.4 $ (53,629.6 ) $ 28,779.7 LIABILITIES AND EQUITY Current liabilities: Current portion of debt $ — $ 99.8 $ — $ 123.1 $ — $ 222.9 Accounts payable — 1.9 27.7 1,695.5 (50.9 ) 1,674.2 Accrued compensation and benefits 0.1 — 10.2 376.4 — 386.7 Other current liabilities — 27.1 71.0 547.0 — 645.1 Intercompany payables 440.2 643.6 440.8 278.5 (1,803.1 ) — Total current liabilities 440.3 772.4 549.7 3,020.5 (1,854.0 ) 2,928.9 Long-term debt due after one year — 6,108.3 1,968.3 1,131.1 — 9,207.7 Intercompany notes payable — 753.3 2,068.0 309.9 (3,131.2 ) — Pension liabilities, net of current portion — — 149.7 155.5 — 305.2 Postretirement benefit liabilities, net of current portion — — 25.9 119.5 — 145.4 Non-recourse liabilities held by special purpose entities — — — 1,136.5 — 1,136.5 Deferred income taxes — — 221.1 2,755.2 (59.4 ) 2,916.9 Other long-term liabilities — 13.0 147.1 1,330.2 — 1,490.3 Redeemable noncontrolling interests — — — 1.3 — 1.3 Total stockholders’ equity 10,630.6 10,417.8 17,065.4 21,101.8 (48,585.0 ) 10,630.6 Noncontrolling interests — — — 16.9 — 16.9 Total equity 10,630.6 10,417.8 17,065.4 21,118.7 (48,585.0 ) 10,647.5 Total liabilities and equity $ 11,070.9 $ 18,064.8 $ 22,195.2 $ 31,078.4 $ (53,629.6 ) $ 28,779.7 CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total ASSETS Current assets: Cash and cash equivalents $ — $ — $ 17.8 $ 133.8 $ — $ 151.6 Accounts receivable — — 31.1 2,201.7 (39.6 ) 2,193.2 Inventories — — 254.3 1,853.2 — 2,107.5 Other current assets — 1.2 11.8 483.2 — 496.2 Intercompany receivables — 227.7 — 1,128.6 (1,356.3 ) — Assets held for sale — — — 25.8 — 25.8 Total current assets — 228.9 315.0 5,826.3 (1,395.9 ) 4,974.3 Property, plant and equipment, net — — 18.9 11,170.6 — 11,189.5 Goodwill — — 1,158.6 6,127.0 — 7,285.6 Intangibles, net — — 1,485.0 2,574.5 — 4,059.5 Restricted assets held by special purpose entities — — — 1,274.3 — 1,274.3 Prepaid pension asset — — — 224.7 — 224.7 Intercompany notes receivable — 155.0 156.9 3,026.8 (3,338.7 ) — Investments in consolidated subsidiaries 11,973.6 18,524.2 20,103.6 — (50,601.4 ) — Other assets — 67.8 185.3 971.8 (76.1 ) 1,148.8 Total assets $ 11,973.6 $ 18,975.9 $ 23,423.3 $ 31,196.0 $ (55,412.1 ) $ 30,156.7 LIABILITIES AND EQUITY Current liabilities: Current portion of debt $ — $ 135.3 $ 108.9 $ 316.9 $ — $ 561.1 Accounts payable — 0.7 31.3 1,839.4 (39.6 ) 1,831.8 Accrued compensation and benefits 0.3 — 14.5 455.6 — 470.4 Other current liabilities — 18.6 83.8 469.4 — 571.8 Intercompany payables 303.4 — 1,052.9 — (1,356.3 ) — Total current liabilities 303.7 154.6 1,291.4 3,081.3 (1,395.9 ) 3,435.1 Long-term debt due after one year — 6,608.0 1,982.9 911.4 — 9,502.3 Intercompany notes payable — 636.3 2,390.5 311.9 (3,338.7 ) — Pension liabilities, net of current portion — — 147.6 146.4 — 294.0 Postretirement benefit liabilities, net of current portion — — 25.7 136.4 — 162.1 Non-recourse liabilities held by special purpose entities — — — 1,145.2 — 1,145.2 Deferred income taxes — — 278.9 2,675.2 (76.1 ) 2,878.0 Other long-term liabilities — 12.9 131.2 909.8 — 1,053.9 Redeemable noncontrolling interests — — — 1.9 — 1.9 Total stockholders’ equity 11,669.9 11,564.1 17,175.1 21,862.2 (50,601.4 ) 11,669.9 Noncontrolling interests — — — 14.3 — 14.3 Total equity 11,669.9 11,564.1 17,175.1 21,876.5 (50,601.4 ) 11,684.2 Total liabilities and equity $ 11,973.6 $ 18,975.9 $ 23,423.3 $ 31,196.0 $ (55,412.1 ) $ 30,156.7 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by operating activities $ 322.3 $ 540.5 $ 171.1 $ 1,036.8 $ — $ 2,070.7 Investing activities: Capital expenditures — — — (978.1 ) — (978.1 ) Investment in unconsolidated entities — — — (1.3 ) — (1.3 ) Proceeds from sale of property, plant and equipment — — 0.1 34.9 — 35.0 Proceeds from property, plant and equipment insurance settlement — 1.5 1.3 3.7 — 6.5 Intercompany notes proceeds — — 5.7 — (5.7 ) — Other — — 14.7 1.7 — 16.4 Net cash provided by (used for) investing activities — 1.5 21.8 (939.1 ) (5.7 ) (921.5 ) Financing activities: Proceeds from issuance of notes — 598.6 — — — 598.6 Additions to revolving credit facilities — 350.0 — 78.0 — 428.0 Repayments of revolving credit facilities — (350.0 ) — (178.2 ) — (528.2 ) Additions to debt — — — 696.4 — 696.4 Repayments of debt — (750.0 ) (105.0 ) (594.2 ) — (1,449.2 ) Changes in commercial paper, net — (339.2 ) — — — (339.2 ) Other financing repayments — (46.0 ) — (34.3 ) — (80.3 ) Issuances of common stock, net of related minimum tax withholdings 22.2 — — — — 22.2 Cash dividends paid to stockholders (344.5 ) — — — — (344.5 ) Cash distributions paid to noncontrolling interests — — — (2.4 ) — (2.4 ) Intercompany notes payments — — — (5.7 ) 5.7 — Other — (5.4 ) — (17.1 ) — (22.5 ) Net cash used for financing activities (322.3 ) (542.0 ) (105.0 ) (57.5 ) 5.7 (1,021.1 ) Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — (28.6 ) — (28.6 ) Increase in cash, cash equivalents and restricted cash — — 87.9 11.6 — 99.5 Cash, cash equivalents and restricted cash at beginning of period — — 17.8 133.8 — 151.6 Cash, cash equivalents and restricted cash at end of period $ — $ — $ 105.7 $ 145.4 $ — $ 251.1 The condensed consolidating statements of cash flows for the year ended September 30, 2020 do not include non-cash transactions between Parent, Issuer, Guarantor Subsidiaries and Non-Guarantor Subsidiaries. From time to time, we may enter into non-cash transactions for simplicity of execution of intercompany transactions. These may include intercompany non-cash capitalizations, intercompany non-cash returns of capital, intercompany debt-to-equity conversions or other transactions of a similar nature. The table below summarizes these non-cash transactions. Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Investing activities: Intercompany notes issued $ — $ (13.9 ) $ (70.4 ) $ (117.0 ) $ 201.3 $ — Intercompany notes proceeds $ — $ — $ 80.6 $ 322.5 $ (403.1 ) $ — Intercompany capital investment $ (407.3 ) $ (625.6 ) $ (990.2 ) $ — $ 2,023.1 $ — Intercompany return of capital $ 442.0 $ 35.6 $ 727.0 $ — $ (1,204.6 ) $ — Financing activities: Intercompany notes borrowing $ — $ 117.0 $ — $ 84.3 $ (201.3 ) $ — Intercompany notes payments $ — $ — $ (322.5 ) $ (80.6 ) $ 403.1 $ — Intercompany capital receipt $ — $ — $ 625.2 $ 1,397.9 $ (2,023.1 ) $ — Intercompany capital distribution $ — $ (442.0 ) $ (21.2 ) $ (741.4 ) $ 1,204.6 $ — Intercompany dividends paid $ — $ — $ (48.3 ) $ (1,287.3 ) $ 1,335.6 $ — CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by (used for) operating activities $ 538.2 $ (203.8 ) $ 442.1 $ 1,533.7 $ — $ 2,310.2 Investing activities: Capital expenditures — — — (1,369.1 ) — (1,369.1 ) Cash paid for purchase of businesses, net of cash acquired — — — (3,374.2 ) — (3,374.2 ) Investment in unconsolidated entities — — — (11.2 ) — (11.2 ) Proceeds from sale of property, plant and equipment — — — 119.1 — 119.1 Proceeds from property, plant and equipment insurance settlement — — — 25.5 — 25.5 Intercompany notes issued — — (0.1 ) (75.7 ) 75.8 — Intercompany notes proceeds — 9.3 6.7 3,870.1 (3,886.1 ) — Intercompany capital investment (563.0 ) (563.0 ) — — 1,126.0 — Other — — 30.2 0.1 — 30.3 Net cash (used for) provided by investing activities (563.0 ) (553.7 ) 36.8 (815.4 ) (2,684.3 ) (4,579.6 ) Financing activities: Proceeds from issuance of notes — 2,498.2 — — — 2,498.2 Additions to revolving credit facilities — 67.2 — 155.0 — 222.2 Repayments to revolving credit facilities — (67.2 ) — (160.0 ) — (227.2 ) Additions to debt — 4,101.8 — 959.8 — 5,061.6 Repayments of debt — (2,400.0 ) (957.5 ) (2,274.1 ) — (5,631.6 ) Changes in commercial paper, net — 339.2 — — — 339.2 Other financing additions — 46.0 — 6.2 — 52.2 Issuances of common stock, net of related minimum tax withholdings 18.3 — — — — 18.3 Purchases of common stock (88.6 ) — — — — (88.6 ) Cash dividends paid to stockholders (467.9 ) — — — — (467.9 ) Cash distributions paid to noncontrolling interests — — — (4.3 ) — (4.3 ) Intercompany notes borrowing — — 75.7 0.1 (75.8 ) — Intercompany notes payments — (3,800.0 ) (70.1 ) (16.0 ) 3,886.1 — Intercompany capital receipt 563.0 — — 563.0 (1,126.0 ) — Other — (27.9 ) — 36.0 — 8.1 Net cash provided by (used for) financing activities 24.8 757.3 (951.9 ) (734.3 ) 2,684.3 1,780.2 Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — 4.0 — 4.0 Decrease in cash, cash equivalents and restricted cash — (0.2 ) (473.0 ) (12.0 ) — (485.2 ) Cash, cash equivalents and restricted cash at beginning of period — 0.2 490.8 145.8 — 636.8 Cash, cash equivalents and restricted cash at end of period $ — $ — $ 17.8 $ 133.8 $ — $ 151.6 The condensed consolidating statements of cash flows for the year ended September 30, 2019 do not include non-cash transactions between Parent, Issuer, Guarantor Subsidiaries and Non-Guarantor Subsidiaries. From time to time, we may enter into non-cash transactions for simplicity of execution of intercompany transactions. These may include intercompany non-cash capitalizations, intercompany non-cash returns of capital, intercompany debt-to-equity conversions or other transactions of a similar nature. The table below summarizes these non-cash transactions. Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Intercompany receivables $ (140.9 ) $ — $ — $ — $ 140.9 $ — Intercompany payables $ — $ — $ — $ 140.9 $ (140.9 ) $ — Investing activities: Intercompany notes issued $ — $ (3,800.0 ) $ (4,667.2 ) $ (10,777.8 ) $ 19,245.0 $ — Intercompany notes proceeds $ — $ 4,519.8 $ 4,536.8 $ 6,822.0 $ (15,878.6 ) $ — Intercompany capital investment $ (10,396.2 ) $ (5,895.5 ) $ (6,889.3 ) $ — $ 23,181.0 $ — Intercompany return of capital $ 606.7 $ 1,479.6 $ 1,032.7 $ — $ (3,119.0 ) $ — Financing activities: Intercompany notes borrowing $ — $ 4,436.3 $ 2,541.5 $ 12,267.2 $ (19,245.0 ) $ — Intercompany notes payments $ — $ — $ (3,022.0 ) $ (12,856.6 ) $ 15,878.6 $ — Intercompany capital receipt $ — $ 10,396.2 $ 5,413.7 $ 7,371.1 $ (23,181.0 ) $ — Intercompany capital distribution $ (563.0 ) $ (606.7 ) $ (457.5 ) $ (1,491.8 ) $ 3,119.0 $ — Intercompany dividends paid $ — $ — $ (302.2 ) $ (1,435.0 ) $ 1,737.2 $ — CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by operating activities $ 4.1 $ 563.4 $ 375.8 $ 1,016.3 $ (28.4 ) $ 1,931.2 Investing activities: Capital expenditures — — (1.2 ) (998.7 ) — (999.9 ) Cash paid for purchase of businesses, net of cash acquired — — — (239.9 ) — (239.9 ) Cash receipts on sold trade receivables — — — 461.6 — 461.6 Investment in unconsolidated entities — — — (114.3 ) — (114.3 ) Proceeds from sale of property, plant and equipment — — — 23.3 — 23.3 Proceeds from property, plant and equipment insurance settlement — — — 7.9 — 7.9 Intercompany notes issued — — (1.4 ) — 1.4 — Intercompany notes proceeds — — 4.5 — (4.5 ) — Intercompany capital investment — (2.0 ) — — 2.0 — Intercompany return of capital — — 82.6 — (82.6 ) — Other — — 18.6 27.6 — 46.2 Net cash (used for) provided by investing activities — (2.0 ) 103.1 (832.5 ) (83.7 ) (815.1 ) Financing activities: Proceeds from issuance of notes — 1,197.3 — — — 1,197.3 Additions to revolving credit facilities — — — 702.4 — 702.4 Repayments to revolving credit facilities — — — (572.2 ) — (572.2 ) Additions to debt — 2.7 — 852.5 — 855.2 Repayments of debt (0.1 ) (1,025.2 ) (22.5 ) (985.1 ) — (2,032.9 ) Other financing repayments — (106.7 ) (8.9 ) (154.3 ) — (269.9 ) Issuances of common stock, net of related minimum tax withholdings — 26.6 — — — 26.6 Purchases of common stock — (195.1 ) — — — (195.1 ) Cash dividends paid to stockholders — (440.9 ) — — — (440.9 ) Cash distributions paid to noncontrolling interests — — — (33.3 ) — (33.3 ) Intercompany notes borrowing — — — 1.4 (1.4 ) — Intercompany notes payments — — — (4.5 ) 4.5 — Intercompany capital receipt — — — 2.0 (2.0 ) — Intercompany capital distribution — — — (82.6 ) 82.6 — Intercompany dividends — — — (28.4 ) 28.4 — Other (4.0 ) (19.9 ) — 31.6 — 7.7 Net cash used for financing activities (4.1 ) (561.2 ) (31.4 ) (270.5 ) 112.1 (755.1 ) Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — (28.2 ) — (28.2 ) Increase (decrease) in cash, cash equivalents and restricted cash — 0.2 447.5 (114.9 ) — 332.8 Cash, cash equivalents and restricted cash at beginning of period — — 43.3 260.7 — 304.0 Cash, cash equivalents and restricted cash at end of period $ — $ 0.2 $ 490.8 $ 145.8 $ — $ 636.8 The condensed consolidating statements of cash flows for the year ended September 30, 2018 do not include non-cash transactions between Parent, Issuer, Guarantor Subsidiaries and Non-Guarantor Subsidiaries. From time to time, we may enter into non-cash transactions for simplicity of execution of intercompany transactions. These may include intercompany non-cash capitalizations, intercompany non-cash returns of capital, intercompany debt-to-equity conversions or other transactions of a similar nature. The table below summarizes these non-cash transactions. Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Investing activities: Intercompany notes issued $ — $ — $ — $ (392.1 ) $ 392.1 $ — Intercompany notes proceeds $ — $ — $ — $ 83.0 $ (83.0 ) $ — Intercompany capital investment $ — $ (755.3 ) $ (335.3 ) $ — $ 1,090.6 $ — Intercompany return of capital $ — $ 1,356.3 $ 766.0 $ — $ (2,122.3 ) $ — Financing activities: Intercompany notes borrowing $ — $ — $ 392.1 $ — $ (392.1 ) $ — Intercompany notes payments $ — $ (69.0 ) $ (14.0 ) $ — $ 83.0 $ — Intercompany capital receipt $ — $ — $ 736.9 $ 353.7 $ (1,090.6 ) $ — Intercompany capital distribution $ — $ — $ (1,356.3 ) $ (766.0 ) $ 2,122.3 $ — Intercompany dividends paid $ — $ — $ — $ (285.9 ) $ 285.9 $ —

Leases

Leases	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	Note 15 . Leases On October 1, 2019, we adopted ASC 842, using the modified retrospective approach and as a result we did not restate prior periods as discussed in “ Note 1. Description of Business and Summary of Significant Accounting Policies — Leased Assets Components of Lease Costs The following table presents certain information related to the lease costs for finance and operating leases (in millions): Year Ended September 30, 2020 Operating lease costs $ 201.2 Variable and short-term lease costs 105.5 Sublease income (6.7 ) Finance lease cost: Amortization of lease assets 10.5 Interest on lease liabilities 7.9 Total lease cost, net $ 318.4 Supplemental Balance Sheet Information Related to Leases The table below presents the lease-related assets and liabilities recorded on the balance sheet (in millions): Consolidated Balance Sheet Caption September 30, 2020 Operating leases: Operating lease right-of-use asset Other assets $ 658.6 Current operating lease liabilities Other current liabilities $ 172.7 Noncurrent operating lease liabilities Other long-term liabilities 545.8 Total operating lease liabilities $ 718.5 Finance leases: Property, plant and equipment $ 143.2 Accumulated depreciation (19.1 ) Property, plant and equipment, net $ 124.1 Current finance lease liabilities Current portion of debt $ 9.0 Noncurrent finance lease liabilities Long-term debt due after one year 265.8 Total finance lease liabilities $ 274.8 Our finance lease portfolio includes certain assets that are either fully depreciated or transferred for which the lease arrangement requires a one-time principal repayment on the maturity date of the lease obligation. Lease Term and Discount Rate September 30, 2020 Weighted average remaining lease term: Operating leases 5.9 years Finance leases 9.0 years Weighted average discount rate: Operating leases 2.6 % Finance leases 4.0 % Supplemental Cash Flow Information Related to Leases The table below presents supplemental cash flow information related to leases (in millions): Year Ended September 30, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows related to operating leases $ 204.1 Operating cash flows related to finance leases $ 7.8 Financing cash flows related to finance leases $ 10.1 ROU assets obtained in exchange for lease liabilities: Operating leases $ 124.4 Maturity of Lease Liabilities The table below reconciles the undiscounted cash flows for each of the first five years and total of the remaining years to the operating lease liabilities and finance lease liabilities recorded on the balance sheet (in millions): September 30, 2020 Operating Leases Finance Leases Total Fiscal 2021 $ 188.7 $ 16.3 $ 205.0 Fiscal 2022 151.4 15.3 166.7 Fiscal 2023 119.1 13.2 132.3 Fiscal 2024 94.1 12.0 106.1 Fiscal 2025 63.2 12.0 75.2 Thereafter 164.4 288.3 452.7 Total lease payments 780.9 357.1 1,138.0 Less: Interest (1) (62.4 ) (82.3 ) (144.7 ) Present value of future lease payments $ 718.5 $ 274.8 $ 993.3 (1) As of September 30, 2019, future minimum lease payments under all noncancelable operating leases for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2020 $ 214.3 Fiscal 2021 180.1 Fiscal 2022 136.3 Fiscal 2023 108.3 Fiscal 2024 85.3 Thereafter 206.1 Total future minimum lease payments $ 930.4 Rental expense for the years ended September 30, 2019 and 2018 was approximately $346.7 million and $243.7 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, 2020
Special Purpose Entities [Abstract]
Special Purpose Entities	Note 16. 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, 2020, the Timber Note was $372.4 million and is included within restricted assets held by special purpose entities on the consolidated balance sheet and the secured financing liability was $326.2 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, 2020, the Installment Note was $895.1 million and is included within restricted assets held by special purpose entities on the consolidated balance sheet and the secured financing liability was $810.3 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, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Note 17. Related Party Transactions We sell products to affiliated companies. Net sales to the affiliated companies for the fiscal years ended September 30, 2020, 2019 and 2018 were approximately $311.5 million, $368.4 million and $418.8 million, respectively. Accounts receivable due from the affiliated companies at September 30, 2020 and 2019 was $23.3 million and $23.0 million, respectively, and was included in accounts receivable on our consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2020
Commitments And Contingencies [Abstract]
Commitments and Contingencies	Note 18. Commitments and Contingencies Capital Additions Estimated costs for future purchases of fixed assets that we are obligated to purchase as of September 30, 2020 total approximately $310 million. Environmental Environmental compliance requirements are a significant factor affecting our business. We employ manufacturing processes that involve discharges to water, air emissions, water intake and waste handling activities. 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. chemical pulping mills in the U.S. and Brazil are subject to more stringent environmental programs and regulations, but all of WestRock’s manufacturing facilities have environmental compliance obligations. On January 31, 2013, the EPA published Boiler MACT. The U.S. Court of Appeals for the District of Columbia Circuit issued a ruling on the consolidated cases challenging Boiler MACT on July 29, 2016 vacating key portions of the rule, including emission limits for certain subcategories of solid fuel boilers, and sending it back to the EPA for further rulemaking. On August 24, 2020 , In addition to Boiler MACT, we are subject to several other federal, state, local and international environmental rules that may impact our business, including other Maximum Achievable Control Technology standards, National Ambient Air Quality Standards for nitrogen oxide, sulfur dioxide, fine particulate matter and ozone for facilities and National Pollutant Discharge Elimination System permitting requirements in the U.S. Legal requirements to review and revise existing environmental regulations applicable to our business, as well as litigation challenging these regulations, could result in more stringent or additional compliance obligations that may require capital investments or increase our operating costs. We are involved in various administrative and other 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. 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 investigation and remediation 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 damages at these or other sites in the future, could result in additional costs. 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 or 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, 2020, we had $5.7 million reserved for environmental liabilities on an undiscounted basis, of which $3.0 million is included in other long-term liabilities and $2.7 million is included in other current liabilities, including amounts accrued in connection with environmental obligations relating to manufacturing facilities that we have closed. We believe the liability for these matters was adequately reserved at September 30, 2020. Climate Change Some of our paper mills, our most energy-intensive manufacturing facilities, burn renewable biomass to generate more than 60 percent of their energy needs based on overall fuel mix. Most of these facilities also self-generate the steam and power needed for their manufacturing processes using combined heat and power or “cogeneration” systems. Our recycling operations help to divert approximately 8 million tons of paper and packaging from landfills where it would otherwise degrade and release greenhouse gases in the form of methane, which has a high global warming potential. Our fiber procurement activities create economic incentives for landowners and family tree farmers to maintain their holdings as working forests that sequester carbon and provide many other environmental benefits, including protection for fresh water supplies and habitats for diverse species of plants and animals. Climate change presents opportunities for our business. For example, the Company produces renewable energy in abundant amounts and generates RECs. An entity seeking to reduce its greenhouse gas profile can purchase our RECs and receive the rights to the environmental attributes of the renewable electricity generated by our integrated Kraft paper mills. The RECs we generate are flexible, market-based tools that support the renewable energy market and advance climate-related sustainability initiatives. Our recycling activities also may present the opportunity to generate offsets that could be used to meet climate-related obligations for ourselves or others. Climate change also presents potential risks and uncertainties for us. With respect to physical climate risks, our manufacturing operations may be impacted by weather-related events such as hurricanes and floods, potentially resulting in lost production, supply chain disruptions and increased material costs. Unpredictable weather patterns also may impact virgin fiber prices, which may fluctuate during prolonged periods of heavy rain or drought. On the other hand, changes in climate also could result in more accommodating weather patterns for greater periods of time in certain areas, which may create favorable fiber market conditions. Climate change may result in regulatory risks as new laws and regulations aimed at mandating GHG reductions come into effect. These rules and regulations could take the form of cap-and-trade, carbon taxes, or GHG reductions mandates for utilities that could increase the cost of purchased electricity. New climate rules and regulations also may result in higher fossil fuel prices and/or fuel efficiency standards that could increase transportation costs. Certain jurisdictions in which we have manufacturing facilities or other investments have already taken actions to address climate change. In the U.S, 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. In addition to these national efforts, some U.S. states in which we have manufacturing operations, including Washington, New York and Virginia, are taking measures to reduce GHG emissions, such as requiring GHG emissions reporting or developing regional cap-and-trade programs. In addition, 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. 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. Other countries in which we conduct business, including China, European Union member states and India, have set GHG reduction targets in accordance with the agreement signed in April 2016 among over 170 countries that established the Paris Agreement, which became effective in November 2016. Regulation related to 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 related laws, regulations and policies to assess the potential impact of such developments on our results of operations, financial condition, cash flows and disclosure obligations. Compliance with climate programs may require future expenditures to meet GHG emission reduction obligations in future years. These obligations may include carbon taxes, the requirement to purchase of GHG credits, or the need to acquire carbon offsets. Also, we may be required to make capital and other investments to displace traditional fossil fuels, such as fuel oil and coal, with lower carbon alternatives, such as biomass and natural gas. 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. Brazil Tax Liability We are challenging claims by the Brazil Federal Revenue Department that we are liable for underpayment of tax, penalties and interest in relation to a claim that a subsidiary of MeadWestvaco Corporation had reduced its tax liability related to the goodwill generated by the 2002 merger of two of its Brazil subsidiaries. The matter has proceeded through the Brazil Administrative Council of Tax Appeals (“ CARF We assert that we have no liability in these matters. The total amount in dispute before CARF and in the annulment actions relating to the claimed tax deficiency was s of September 30, 2020, including various penalties and interest. The U.S. dollar equivalent has fluctuated significantly due to changes in exchange rates. The amount of o ur uncertain tax position reserve for this matter, that excludes certain penalties, is included in the unrecognized tax benefits table. See “ Note 6. Income Taxes ”. Resolution of the uncertain tax positions could have a material adverse effect on our cash flows and results of operations or materially benefit our results of operations in future periods depending upon their ultimate resolution. Guarantees We make certain guarantees in the normal 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 our exposure to these matters could be approximately $50 million. As of September 30, 2020, we had recorded $9.6 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. Indirect Tax Claim In March 2017, the Supreme Court of Brazil issued a decision concluding that certain state value added tax should not be included in the calculation of federal gross receipts taxes. Subsequently, in fiscal 2019, the Supreme Court of Brazil rendered favorable decisions on six of our cases granting us the right to recover certain state value added tax. The tax authorities in Brazil have filed a Motion of Clarification with the Supreme Court of Brazil and the timing of the decision is unknown at this time. However, based on our preliminary evaluation and the opinion of our tax and legal advisors, we believe the decision reduced our gross receipts tax in Brazil prospectively and retrospectively, and will allow us to recover tax amounts collected by the government. Due to the volume of invoices being reviewed (January 2002 to September 2019), we have recorded the estimated recoveries across several periods beginning in the fourth quarter of fiscal 2019 as we have reviewed the documents and the amount has become estimable. In fiscal 2020, we recorded a $51.9 million receivable for our expected recovery and interest that consisted primarily of a $32.1 million reduction of cost of goods sold and $20.5 million reduction of interest expense, net. In fiscal 2019, we recorded a $12.2 million receivable for our expected recovery and interest that consisted primarily of cost of goods sold. We are monitoring the status of our remaining cases, and subject to the resolution in the courts, we may record additional amounts in future periods.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss and Other Comprehensive Loss	12 Months Ended
	Sep. 30, 2020
Other Comprehensive Income Loss [Abstract]
Accumulated Other Comprehensive Loss and Other Comprehensive Loss	Note 19. Accumulated Other Comprehensive Loss and Other Comprehensive Loss The following table summarizes the changes in accumulated other comprehensive loss by component for the fiscal years ended September 30, 2020 and 2019 (in millions): Deferred (Loss) Income on Cash Flow Hedges Defined Benefit Pension and Postretirement Plans Foreign Currency Items Total (1) Balance at September 30, 2018 $ (0.2 ) $ (465.9 ) $ (229.2 ) $ (695.3 ) Other comprehensive income (loss) before reclassifications 1.1 (250.7 ) (142.7 ) (392.3 ) Amounts reclassified from accumulated other comprehensive (income) loss (0.2 ) 18.6 — 18.4 Net current period other comprehensive income (loss) 0.9 (232.1 ) (142.7 ) (373.9 ) Balance at September 30, 2019 $ 0.7 $ (698.0 ) $ (371.9 ) $ (1,069.2 ) Other comprehensive (loss) income before reclassifications (9.9 ) 5.1 (214.7 ) (219.5 ) Amounts reclassified from accumulated other comprehensive loss 3.6 38.6 — 42.2 Net current period other comprehensive (loss) income (6.3 ) 43.7 (214.7 ) (177.3 ) Reclassification of stranded tax effects — (73.4 ) — (73.4 ) Balance at September 30, 2020 $ (5.6 ) $ (727.7 ) $ (586.6 ) $ (1,319.9 ) (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, 2020 and 2019 (in millions): Years Ended September 30, 2020 2019 Pre-Tax Tax Net of Tax Pre-Tax Tax Net of Tax Amortization of defined benefit pension and postretirement items: (1) Actuarial losses (2) $ (47.7 ) 12.8 $ (34.9 ) $ (22.7 ) 5.9 $ (16.8 ) Prior service costs (2) (5.0 ) 1.3 (3.7 ) (2.4 ) 0.6 (1.8 ) Reclassification of stranded tax effects (3) — 73.4 73.4 — — — Subtotal defined benefit plans (52.7 ) 87.5 34.8 (25.1 ) 6.5 (18.6 ) Derivative Instruments: (1) Interest rate swap hedge (loss) gain (4) (2.3 ) 0.6 (1.7 ) 0.3 (0.1 ) 0.2 Natural gas commodity hedge loss (5) (2.6 ) 0.7 (1.9 ) — — — Subtotal derivative instruments (4.9 ) 1.3 (3.6 ) 0.3 (0.1 ) 0.2 Total reclassifications for the period $ (57.6 ) $ 88.8 $ 31.2 $ (24.8 ) $ 6.4 $ (18.4 ) (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 5. Retirement Plans (3) Amount reclassified to retained earnings as a result of the adoption of ASU 2018-02. (4) These accumulated other comprehensive income components are included in Interest expense, net. (5) These accumulated other comprehensive income components are included in Cost of goods sold. A summary of the components of other comprehensive (loss) income, including noncontrolling interest, for the years ended September 30, 2020, 2019 and 2018, is as follows (in millions): Fiscal 2020 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (215.0 ) $ — $ (215.0 ) Deferred loss on cash flow hedges (13.3 ) 3.3 (10.0 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 4.9 (1.3 ) 3.6 Net actuarial gain arising during period 34.6 (10.4 ) 24.2 Amortization and settlement recognition of net actuarial loss 48.3 (12.9 ) 35.4 Prior service cost arising during the period (26.9 ) 7.3 (19.6 ) Amortization of prior service cost 5.1 (1.3 ) 3.8 Consolidated other comprehensive loss (162.3 ) (15.3 ) (177.6 ) Less: Other comprehensive loss attributable to noncontrolling interests 0.3 — 0.3 Other comprehensive loss attributable to common stockholders $ (162.0 ) $ (15.3 ) $ (177.3 ) Fiscal 2019 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (143.4 ) $ — $ (143.4 ) Deferred gain on cash flow hedges 1.5 (0.4 ) 1.1 Reclassification adjustment of net gain on cash flow hedges included in earnings (0.3 ) 0.1 (0.2 ) Net actuarial loss arising during period (335.9 ) 87.4 (248.5 ) Amortization and settlement recognition of net actuarial loss 23.3 (6.1 ) 17.2 Prior service cost arising during the period (3.9 ) 0.6 (3.3 ) Amortization of prior service cost 2.4 (0.6 ) 1.8 Consolidated other comprehensive loss (456.3 ) 81.0 (375.3 ) Less: Other comprehensive loss attributable to noncontrolling interests 1.5 (0.1 ) 1.4 Other comprehensive loss attributable to common stockholders $ (454.8 ) $ 80.9 $ (373.9 ) 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 )

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Stockholders' Equity	Note 20. 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 2020, we repurchased no shares of our Common Stock. In fiscal 2019, we repurchased approximately 2.1 million shares of our Common Stock for an aggregate cost of $88.6 million. In fiscal 2018, we repurchased approximately 3.4 million shares of our Common Stock for an aggregate cost of $195.1 million. As of September 30, 2020, we had remaining authorization under the repurchase program authorized in July 2015 to purchase approximately 19.1 million shares of our Common Stock.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Sep. 30, 2020
Stock Based Compensation [Abstract]
Stock Based Compensation	Note 21. 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 Our results of operations for the fiscal years ended September 30, 2020, 2019 and 2018 include share-based compensation expense of $130.3 million, $64.2 million and $66.8 million, respectively. The total income tax benefit in the results of operations in connection with share-based compensation was $33.2 million, $16.3 million and $19.4 million, for the fiscal years ended September 30, 2020, 2019 and 2018, respectively. Cash received from share-based payment arrangements for the fiscal years ended September 30, 2020, 2019 and 2018 was $32.4 million, $61.5 million and $44.4 million, respectively. Equity Awards Issued in Connection with Acquisitions In connection with the KapStone Acquisition, we replaced certain outstanding awards of restricted stock units granted under the KapStone long-term incentive plan with WestRock stock options and restricted stock units. No additional shares will be granted under the KapStone plan. The KapStone equity awards were replaced with awards with identical terms utilizing an approximately 0.83 conversion factor as described in the Merger Agreement. The acquisition consideration included approximately $70.8 million related to outstanding KapStone equity awards related to service prior to the effective date of the KapStone Acquisition – the balance related to service after the effective date are being expensed over the remaining service period of the awards. As part of the KapStone Acquisition, we issued 2,665,462 options that were valued at a weighted average fair value of $20.99 per share using the Black-Scholes option pricing model. The weighted average significant assumptions used were: 2019 Expected term in years 3.1 Expected volatility 27.7 % Risk-free interest rate 3.0 % Dividend yield 4.1 % 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. 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. Other than in connection with replacement awards in connection with acquisitions, we did not grant any stock options in fiscal 2020, 2019 and 2018. The table below summarizes the changes in all stock options during the fiscal year ended September 30, 2020: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2019 4,396,177 $ 33.32 Exercised (840,433 ) 24.84 Expired (93,691 ) 38.21 Forfeited (5,756 ) 26.59 Outstanding at September 30, 2020 3,456,297 $ 35.26 3.0 $ 12.9 Exercisable at September 30, 2020 3,455,580 $ 35.27 3.0 $ 12.9 Vested and expected to vest at September 30, 2020 3,456,297 $ 35.26 3.0 $ 12.9 The aggregate intrinsic value of options exercised during the years ended September 30, 2020, 2019 and 2018 was $11.8 million, $44.5 million and $67.4 million, respectively. As of September 30, 2020, there was less than $0.1 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 0.2 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, 2020: SARs Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2019 34,972 $ 28.41 Exercised (15,343 ) 27.00 Expired (2,647 ) 23.65 Outstanding at September 30, 2020 16,982 $ 30.42 1.1 $ 0.1 Exercisable at September 30, 2020 16,982 $ 30.42 1.1 $ 0.1 The aggregate intrinsic value of SARs exercised during the years ended September 30, 2020, 2019 and 2018 was $0.2 million, zero and $0.5 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 such as Cash Flow Per Share 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. In fiscal 2020, in connection with the WestRock Pandemic Action Plan we issued restricted stock grants to satisfy certain annual bonus incentives. Those awards vested in October 2020 at 105 % of target. The table below summarizes the changes in unvested restricted stock during the fiscal year ended September 30, 2020: Shares/Units Weighted Average Grant Date Fair Value Unvested at September 30, 2019 (1) 3,645,538 $ 51.94 Granted 4,446,175 31.53 Vested (766,431 ) 51.39 Forfeited (709,915 ) 51.27 Unvested at September 30, 2020 (1) 6,615,367 $ 38.36 (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 aggregate outstanding grants to be attained at levels less than target. However, it is possible that the performance attained may vary. There was approximately $81.6 million of unrecognized compensation cost related to all unvested restricted shares as of September 30, 2020 that will be recognized over a weighted average remaining vesting period of 1.0 years. The following table represents a summary of restricted stock shares granted in fiscal 2020, 2019 and 2018 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. 2020 2019 2018 Shares of restricted stock granted to non-employee directors (1) 49,236 39,792 23,285 Shares of restricted stock granted to employees: Shares granted for attainment of a performance condition at an amount in excess of target (2) — 1,149,592 45,964 Shares granted with a service condition and a Cash Flow Per Share performance condition at target (3) 869,065 652,465 432,655 Shares granted with a service condition and a relative Total Shareholder Return market condition at target (3) 152,595 407,300 259,695 Shares granted with a service condition (4) 889,030 682,264 354,512 Shares of restricted stock granted for annual bonus 2,486,249 — — Share of restricted stock assumed in purchase accounting: Shares granted with a service condition (5) — 742,032 — Total restricted stock granted 4,446,175 3,673,445 1,116,111 (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) These shares vest over approximately three to four years. (5) These shares vest over approximately one to three years. The employee grants with a relative Total Shareholder Return market condition in fiscal 2020 were valued using a Monte Carlo simulation at $45.14 per share. The significant assumptions used in valuing these grants included: an expected term of 3.0 years, an expected volatility of 27.5% and a risk-free interest rate of 1.3%. 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 2019 were valued using a Monte Carlo simulation at $42.64 per share. The significant assumptions used in valuing these grants included: an expected term of 2.9 years, an expected volatility of 27.2% and a risk-free interest rate of 2.4%. 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 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. 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 2020, 2019 and 2018 (in millions, except shares): 2020 2019 2018 Shares of restricted stock vested 766,431 2,933,556 697,717 Aggregate fair value of restricted stock vested $ 29.6 $ 115.2 $ 46.1 The shares vested in fiscal 2020 reflect the vesting of the fiscal 2017 grants, with a Cash Flow Per Share performance condition that vested at 98.8% of target, as well as certain shares with a service condition. The shares vested in fiscal 2019 reflect the vesting of the fiscal 2016 grants, with a Cash Flow Per Share performance condition that vested at 200% of target, as well as certain shares with a performance and/or service condition. 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. 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, 2020
Earnings Per Share [Abstract]
Earnings per Share	Note 22. Earnings per Share The restricted stock awards that 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, 2020 2019 2018 Numerator: Net (loss) income attributable to common stockholders $ (690.9 ) $ 862.9 $ 1,906.1 Less: Distributed and undistributed income available to participating securities (0.1 ) (0.1 ) (0.2 ) Distributed and undistributed (loss) income available to common stockholders $ (691.0 ) $ 862.8 $ 1,905.9 Denominator: Basic weighted average shares outstanding 259.2 256.6 255.5 Effect of dilutive stock options and non-participating securities — 2.5 4.3 Diluted weighted average shares outstanding 259.2 259.1 259.8 Basic (loss) earnings per share attributable to common stockholders $ (2.67 ) $ 3.36 $ 7.46 Diluted (loss) earnings per share attributable to common stockholders $ (2.67 ) $ 3.33 $ 7.34 Options and restricted stock in the amount of 4.2 million, 1.3 million and 0.2 million common shares in fiscal 2020, 2019 and 2018, 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, 2020
Financial Results By Quarter Unaudited [Abstract]
Financial Results by Quarter	Note 23. Financial Results by Quarter (Unaudited) Fiscal 2020 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 4,423.7 $ 4,447.3 $ 4,236.3 $ 4,471.5 Gross profit $ 809.0 $ 804.8 $ 770.0 $ 813.4 (Gain) loss on disposal of assets $ (1.3 ) $ (5.6 ) $ 1.0 $ (10.4 ) Multiemployer pension withdrawal expense (income) $ — $ 0.9 $ (2.0 ) $ — Restructuring and other costs $ 30.1 $ 16.4 $ 9.7 $ 56.5 Goodwill impairment $ — $ — $ — $ 1,333.2 Loss on extinguishment of debt $ — $ (0.5 ) $ (0.6 ) $ (0.4 ) Income tax expense $ (46.5 ) $ (57.8 ) $ (19.2 ) $ (40.0 ) Consolidated net income (loss) $ 139.5 $ 148.9 $ 180.0 $ (1,154.5 ) Net income (loss) attributable to common stockholders $ 138.5 $ 148.1 $ 178.5 $ (1,156.0 ) Basic earnings (loss) per share attributable to common stockholders $ 0.54 $ 0.57 $ 0.69 $ (4.45 ) Diluted earnings (loss) per share attributable to common stockholders $ 0.53 $ 0.57 $ 0.69 $ (4.45 ) Fiscal 2019 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 4,327.4 $ 4,620.0 $ 4,690.0 $ 4,651.6 Gross profit $ 781.8 $ 899.6 $ 988.9 $ 1,078.7 (Gain) loss on disposal of assets $ (43.8 ) $ — $ 6.5 $ (3.9 ) Multiemployer pension withdrawal income $ — $ — $ (1.7 ) $ (4.6 ) Land and Development impairments $ — $ 13.0 $ — $ — Restructuring and other costs $ 54.4 $ 34.8 $ 17.9 $ 66.6 (Loss) gain on extinguishment of debt $ (1.9 ) $ 0.4 $ (3.2 ) $ (0.4 ) Income tax expense $ (62.7 ) $ (47.2 ) $ (77.6 ) $ (89.3 ) Consolidated net income $ 139.8 $ 161.9 $ 253.8 $ 312.4 Net income attributable to common stockholders $ 139.1 $ 160.4 $ 252.6 $ 310.8 Basic earnings per share attributable to common stockholders $ 0.55 $ 0.63 $ 0.98 $ 1.21 Diluted earnings per share attributable to common stockholders $ 0.54 $ 0.62 $ 0.98 $ 1.20 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 2020 financial results by quarter (unaudited) table was increased by $33.8 million pre-tax for our expected recovery and interest related to an indirect tax claim and increased by $29.5 million pre-tax related to Hurricane Michael insurance proceeds received. Basic and diluted earnings per share attributable to common stockholders were increased by approximately $0.18 and $0.17 per share, respectively for these items. See “ Note 18. Commitments and Contingencies — Indirect Tax Claim ” “ Note 7. Segment Information ” for more information. Consolidated net income in the third quarter of fiscal 2020 financial results by quarter (unaudited) table was decreased by $31.6 million pre-tax for one-time COVID-19 recognition awards to our teammates who work in manufacturing operations. Basic and diluted earnings per share attributable to common stockholders were each decreased by approximately $0.09 per share. Consolidated net loss in the fourth quarter of fiscal 2020 financial results by quarter (unaudited) table was driven by a pre-tax non-cash goodwill impairment of $1,333.2 million, or $1,314.3 million after-tax, in our Consumer Packaging reporting unit. The goodwill impairment contributed a loss of $5.06 per share each to the basic and diluted loss per share attributable to common stockholders. See “ Note 1. Description of Business and Summary of Significant Accounting Policies — Goodwill and Long-Lived Assets ” for more information. Consolidated net income in the first quarter of fiscal 2019 financial results by quarter (unaudited) table was decreased by $39.8 million pre-tax of direct expenses from Hurricane Michael (net of $20.0 million of insurance proceeds) and an estimated $31.4 million pre-tax of lost production and sales. Additionally, consolidated net income in the first quarter was decreased by $24.7 million pre-tax of expense for inventory stepped-up in purchase accounting related to the KapStone Acquisition and increased by a $48.5 million pre-tax gain on sale of our Atlanta beverage facility. Basic and diluted earnings per share attributable to common stockholders were decreased by approximately $0.14 and $0.14 per share, respectively for these items. Consolidated net income in the fourth quarter of fiscal 2019 financial results by quarter (unaudited) table was increased by $63.4 million pre-tax related to Hurricane Michael as $70.0 million of insurance proceeds were partially offset by $6.6 million of direct expenses. Basic and diluted earnings per share attributable to common stockholders were increased by approximately $0.19 and $0.18 per share, respectively for these items.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2020
Description Of Business And Summary Of Significant Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The consolidated financial statements are prepared in accordance with GAAP and, in certain cases, include amounts based on management's prudent judgments and estimates. Actual results may differ from these estimates. The consolidated financial statements include the accounts of WestRock and our partially owned subsidiaries for which we have a controlling financial interest, including variable interest entities for which we are the primary beneficiary. 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 without a readily determinable value in which we are not able to exercise significant influence over the investee are accounted under the measurement alternative (i.e. cost less impairment, adjusted for any qualifying observable price changes). Our equity and cost method investments are not material either individually or in the aggregate. We have eliminated all significant intercompany accounts and transactions. See “ Note 7. Segment Information
Reclassifications and Adjustments	Reclassifications and Adjustments During fiscal 2020, we evaluated our revolving credit facilities and determined that the borrowings and repayments for certain facilities should be presented gross instead of net on the consolidated statements of cash flow and corrected the presentation of the prior years by an immaterial amount. Certain amounts in prior periods have been reclassified to conform with the current year presentation.
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 estimating the fair value of assets and liabilities of acquired businesses. 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. The global impact of the COVID-19 pandemic may also affect our accounting estimates, which may materially change from period to period due to changing market factors. We regularly evaluate these significant factors and make adjustments where facts and circumstances dictate.
Revenue Recognition	Revenue Recognition We generally recognize revenue on a point-in-time basis when the customer takes title to the goods and assumes the risks and rewards for the goods, which coincide with the transfer of control of our goods to the customer. Additionally, we manufacture certain customized products that have no alternative use to us (since they 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 products, including a reasonable profit. For products that meet these two criteria, we recognize revenue “over time”. This results in revenue recognition prior to the date of shipment or title transfer for these products and increases the contract asset (unbilled receivables) balance with a corresponding reduction in finished goods inventory on our balance sheet. We net, against our gross sales, provisions for discounts, returns, allowances, customer rebates and other adjustments. Such adjustments are based on historical experience which is consistent with the most likely method as provided in ASC 606 “ Revenue from Contracts with Customers ASC 606 As permitted by ASC 606, we have elected to treat costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset we would recognize is one year or less. We do not record interest income when the difference in timing of control transfer and customer payment is one year or less. We also 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.
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 since we treat shipping and handling as fulfilment activities.
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 of our cash and cash equivalents approximate fair market values. We place our cash and cash equivalents primarily 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 average of our receivables collection is within 30 to 60 days. We sell certain receivables under our A/R Sales Agreement (as hereinafter defined). See “ Note 12. Fair Value — Accounts Receivable 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 charge off receivables when they are determined to be no longer collectible. Bad debt expense was $19.9 million, $10.0 million and $4.2 million in fiscal 2020, 2019 and 2018, respectively. 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 2020, 2019 and 2018 (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 53.2 $ 49.7 $ 45.8 Reduction in sales and charges to costs and expenses 270.8 259.6 202.8 Deductions (257.7 ) (256.1 ) (198.9 ) Balance at end of fiscal year $ 66.3 $ 53.2 $ 49.7
Inventories	Inventories We value our U.S. inventories at the lower of cost or market, with cost for the majority of our U.S. inventories determined on the last-in first-out (“ LIFO 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.
Leased Assets	Leased Assets We adopted the provisions of ASC 842 on October 1, 2019 using the modified retrospective approach and, as a result, did not restate prior periods. See “ Note 15. Leases ” for additional details. We record our operating lease ROU assets and liabilities at the commencement date of the lease based on the present value of lease payments over the lease term. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Our leases may include options to extend or terminate the lease. These options to extend are included in the lease term when it is reasonably certain that we will exercise that option. While some leases provide for variable payments, they are not included in the ROU assets and liabilities because they are not based on an index or rate. Variable payments for real estate leases primarily relate to common area maintenance, insurance, taxes and utilities. Variable payments for equipment, vehicles and leases within supply agreements primarily relate to usage, repairs, and maintenance. As the implicit rate is not readily determinable for our leases, we apply a portfolio approach using an estimated incremental borrowing rate to determine the initial present value of lease payments over the lease terms on a collateralized basis over a similar term, which is based on market and company specific information. We use the unsecured borrowing rate and risk-adjust that rate to approximate a collateralized rate, and apply the rate based on the currency of the lease, which is updated on a quarterly basis for measurement of new lease liabilities. We have made an accounting policy election to not recognize ROU assets and liability for leases with a term of 12 months or less unless the lease includes an option to renew or purchase the underlying asset that are reasonably certain to be exercised. In addition, the Company has applied the practical expedient to account for the lease and non-lease components as a single lease component for all of the Company's leases. See “ Note 15. Leases ” for additional information .
Property, Plant and Equipment	Property, Plant and Equipment We record 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 2020, 2019 and 2018, we capitalized interest of approximately $24.6 million, $23.8 million and $8.2 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 useful 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	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.” ASC 350 allows an optional qualitative assessment, prior to a quantitative assessment test, to determine whether it is more likely than not that the fair value of a reporting unit exceeds its carrying amount. We generally do not attempt a qualitative assessment and move directly to the quantitative test. As part of the quantitative test, we utilize the present value of expected cash flows or, as appropriate, a combination of the present value of expected 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 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 past 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, which we believe would be generally consistent with that of a market participant. 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 are 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 is 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 measure goodwill impairment charge based on the excess of a reporting unit’s carrying amount over its fair value as required under ASU 2017-04, which we early adopted starting with our fiscal 2020 annual goodwill impairment test on July 1, 2020. We began seeing the impact of COVID-19 in a limited manner at the end of the second quarter of fiscal 2020. The impact on our operations increased in the third quarter of fiscal 2020. During these interim periods, we evaluated the current economic environment, including our then current assessment of the long-term impact of COVID-19 on our forecasts, and we concluded there were no indicators of impairment of our long-lived assets, including goodwill that required a quantitative test to be performed. During the fourth quarter of fiscal 2020, we completed our annual goodwill impairment testing. We considered factors such as, but not limited to, our expectations for the short-term and long-term impacts of COVID-19, macroeconomic conditions, industry and market considerations, and financial performance, including planned revenue, earnings and capital investments of each reporting unit. 10% The impairment was driven by the expected lower volumes and cash flows related to certain external SBS end markets, including commercial print, tobacco and plate and cup stock markets e believe these declines are more systemic and our view of related growth and earnings opportunities has been diminished for the foreseeable future. “ Risk Factors ” We follow the provisions included in ASC 360, “Property, Plant and Equipment” greater than the fair value of the asset. We estimate fair value using discounted cash flows, observable prices for similar assets, or other valuation techniques. We record assets classified as “held for sale” at the lower of their carrying value or estimated fair value less anticipated costs to sell. 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 15.5 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 likely that we will 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, contractual obligations, and the adjustments of property, plant and equipment and lease ROU assets to their fair 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 4. 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 The acquisition method of accounting also requires us to refine these estimates over a measurement period not to exceed one year to reflect new information obtained about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date. If we are required to adjust provisional amounts that we have recorded for the fair values of assets and liabilities in connection with acquisitions, these adjustments could have a material impact on our financial condition and results of operations. 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 future 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 5. Retirement Plans ” Supplemental Plans We measure certain nonfinancial assets and nonfinancial liabilities at fair value on a nonrecurring basis. These assets and liabilities include equity method investments when they are deemed to be other-than-temporarily impaired, investments for which the fair value measurement alternative is elected, assets acquired and liabilities assumed 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, property, plant and equipment, ROU assets related to operating leases, goodwill and other intangible assets that are written down to fair value when they are held for sale or determined to be impaired. See “ Note 4. Restructuring and Other Costs “ 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 entire change in fair value of 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. 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, 2020, the notional amounts of interest rate and foreign currency exchange contract derivatives were $600.0 million and $250.2 million, respectively. The fair value of these derivative instruments was not significant as of September 30, 2020. At September 30, 2020, no natural gas commodity derivatives were outstanding. At September 30, 2019, the notional amounts of interest rate and foreign currency exchange contract derivatives were $600.0 million and $351.0 million, respectively. At September 30, 2019, the notional amount of natural gas commodity derivatives was 8.4 MMBtu. 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 . 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 (as hereinafter defined) was signed into law. The Tax Act contained 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 6. Income Taxes.
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits We account for pension and other postretirement benefits in accordance with ASC 715, “ Compensation – Retirement Benefits “ Note 5. 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 WestRock Pandemic Action Plan we issued restricted stock grants to the majority of our employees to replace their annual cash bonus. See “ Note 21. Share-Based Compensation ” for additional information.
Asset Retirement Obligations	Asset Retirement Obligations We account 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, 2020 and 2019 were $118.2 million and $124.3 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 $6.6 million, $18.5 million and $12.2 million i
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 18. Commitments and Contingencies.
New Accounting Standards	New Accounting Standards — Adopted in fiscal 2020 In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Test for Goodwill Impairment “Intangibles Goodwill and Other” We early adopted the provisions of this ASU starting with our fiscal 2020 annual goodwill impairment test on July 1, 2020. within “ Note 1. Description of Business and Summary of Significant Accounting Policies — Goodwill and Long-Lived Assets ”. 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 ASU 2018-02 Tax Act In February 2016, the FASB issued ASU 2016-02 “ Leases”, Leases We adopted the provisions of ASC 842 on October 1, 2019 using the modified retrospective approach and, as a result, did not restate prior periods. See “ Note 15. Leases ” for additional details. New Accounting Standards — Pending to be Adopted in Fiscal 2021 In October 2018, the FASB issued ASU 2018-18 “ Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 Collaborative arrangements ASC 808 ASC In October 2018, the FASB issued ASU 2018-17 “ Consolidation: Targeted Improvements to Related Party Guidance for Variable Interest Entities 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 retrospectively. This ASU is effective for fiscal years ending after December 15, 2020 (fiscal 2021 for us). Early adoption is permitted. We do not expect the adoption of this ASU to have a material impact on our consolidated financial statements. In June 2016, the FASB issued ASU 2016-13 “ Financial Instruments – Credit losses: Measurement of Credit Losses on financial Instruments (Topic 326) ASU 2016-13 Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ASU 2019-04 “Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief” ASU 2019-05 Codification Improvements to Topic 326, Financial Instruments – Credit Losses ASU 2019-11 Financial Instruments – Credit Losses (Topic 326) and Leases (Topic 842) ASU 2020-02 New Accounting Standards — Recently Issued In March 2020, the FASB issued ASU 2020-04 “ Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” In December 2019, the FASB issued ASU 2019-12 “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes”

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2020
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 2020, 2019 and 2018 (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 53.2 $ 49.7 $ 45.8 Reduction in sales and charges to costs and expenses 270.8 259.6 202.8 Deductions (257.7 ) (256.1 ) (198.9 ) Balance at end of fiscal year $ 66.3 $ 53.2 $ 49.7
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

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Sep. 30, 2020
Revenue From Contract With Customer [Abstract]
Schedule of Disaggregates Revenue by Geographical Market and Product Type (Segment)	The tables below disaggregate our revenue by geographical market and product type (segment). Year Ended September 30, 2020 (In millions) Corrugated Packaging Consumer Packaging Land and Development Intersegment Sales Total Primary Geographical Markets North America $ 10,975.8 $ 4,978.2 $ 18.9 $ (191.4 ) $ 15,781.5 South America 393.1 70.1 — — 463.2 Europe 7.9 1,006.4 — (0.3 ) 1,014.0 Asia Pacific 42.4 278.3 — (0.6 ) 320.1 Total $ 11,419.2 $ 6,333.0 $ 18.9 $ (192.3 ) $ 17,578.8 Year Ended September 30, 2019 (In millions) Corrugated Packaging Consumer Packaging Land and Development Intersegment Sales Total Primary Geographical Markets North America $ 11,314.7 $ 5,166.6 $ 23.4 $ (155.5 ) $ 16,349.2 South America 437.2 73.2 — — 510.4 Europe 1.6 1,064.7 — (0.1 ) 1,066.2 Asia Pacific 63.2 301.5 — (1.5 ) 363.2 Total $ 11,816.7 $ 6,606.0 $ 23.4 $ (157.1 ) $ 18,289.0
Summary of Opening and Closing Balances of Contract Assets and Contract Liabilities	The opening and closing balances of our contract assets and contract liabilities are as follows. Contract assets and contract liabilities are reported within Other current assets and Other current liabilities, respectively, on the consolidated balance sheet. (In millions) Contract Assets (Short-Term) Contract Liabilities (Short-Term) Beginning balance - October 1, 2019 $ 188.0 $ 7.7 Ending balance - September 30, 2020 185.8 12.0 (Decrease) / increase $ (2.2 ) $ 4.3

Acquisitions and Investments (T

Acquisitions and Investments (Tables) - KapStone Acquisition [Member]	12 Months Ended
	Sep. 30, 2020
Acquired Finite Lived Intangible Assets [Line Items]
Summary of Fair Values of Assets Acquired and Liabilities Assumed by Major Class of Assets and Liabilities and Measurement Period Adjustments	The following table summarizes the fair values of the assets acquired and liabilities assumed in the KapStone Acquisition by major class of assets and liabilities as of the acquisition date, as well as adjustments made during fiscal 2019 and fiscal 2020 (referred to as “ measurement period adjustments Amounts Recognized as of the Acquisition Date Measurement Period Adjustments (1) Amounts Recognized as of Acquisition Date (as Adjusted) (2) Cash and cash equivalents $ 8.6 $ — $ 8.6 Current assets, excluding cash and cash equivalents 878.9 (30.2 ) 848.7 Property, plant and equipment, net 1,910.3 11.5 1,921.8 Goodwill 1,755.0 0.5 1,755.5 Intangible assets 1,336.1 30.3 1,366.4 Other long-term assets 27.9 (0.1 ) 27.8 Total assets acquired 5,916.8 12.0 5,928.8 Current portion of debt 33.3 — 33.3 Current liabilities 337.5 7.9 345.4 Long-term debt due after one year 1,333.4 — 1,333.4 Accrued pension and other long-term benefits 9.8 2.8 12.6 Deferred income taxes 609.7 (1.4 ) 608.3 Other long-term liabilities 118.4 2.7 121.1 Total liabilities assumed 2,442.1 12.0 2,454.1 Net assets acquired $ 3,474.7 $ — $ 3,474.7 (1) (2) The measurement period adjustments were primarily due to refinements to third party appraisals and carrying amounts of certain assets and liabilities, as well as adjustments to certain tax accounts based on, among other things, adjustments to deferred tax liabilities. The net impact of the measurement period adjustments to goodwill were essentially flat.
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The following table summarizes the weighted average life and the fair value of intangible assets recognized in the KapStone Acquisition, excluding goodwill (in millions, except lives): Weighted Avg. Life Amounts Recognized as of the Acquisition Date Customer relationships 11.7 $ 1,303.0 Trademarks and tradenames 16.9 54.2 Favorable contracts 6.0 9.2 Total 11.9 $ 1,366.4

Restructuring and Other Costs (

Restructuring and Other Costs (Tables)	12 Months Ended
	Sep. 30, 2020
Restructuring And Other Costs [Abstract]
Schedule of Restructuring and Other Costs	The following table summarizes our Restructuring and other costs for fiscal 2020, 2019 and 2018 (in millions): 2020 2019 2018 Restructuring $ 93.7 $ 111.0 $ 39.5 Other 19.0 62.7 65.9 Restructuring and Other Costs $ 112.7 $ 173.7 $ 105.4
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): 2020 2019 2018 Cumulative Total Expected Corrugated Packaging Net property, plant and equipment costs $ 2.2 $ 32.1 $ 2.9 $ 96.3 $ 96.3 Severance and other employee costs 8.7 16.9 1.9 43.2 43.2 Equipment and inventory relocation costs 2.2 4.8 3.4 10.4 10.9 Facility carrying costs 2.6 3.9 3.3 21.1 23.2 Other costs (1.9 ) 1.2 0.1 3.3 3.3 Restructuring total $ 13.8 $ 58.9 $ 11.6 $ 174.3 $ 176.9 Consumer Packaging Net property, plant and equipment costs $ 23.5 $ 0.5 $ 6.8 $ 53.1 $ 53.1 Severance and other employee costs 19.8 6.0 6.9 58.3 58.3 Equipment and inventory relocation costs 1.4 1.0 2.4 7.3 7.3 Facility carrying costs — 0.2 0.9 1.9 1.9 Other costs 10.5 4.3 2.0 19.1 19.4 Restructuring total $ 55.2 $ 12.0 $ 19.0 $ 139.7 $ 140.0 Land and Development Net property, plant and equipment costs $ — $ — $ — $ 1.8 $ 1.8 Severance and other employee costs — 0.1 0.3 13.8 13.8 Other costs 2.0 — 3.0 5.0 5.0 Restructuring total $ 2.0 $ 0.1 $ 3.3 $ 20.6 $ 20.6 Corporate Severance and other employee costs $ 21.1 $ 37.5 $ 0.8 $ 59.4 $ 59.4 Other costs 1.6 2.5 4.8 9.0 9.0 Restructuring total $ 22.7 $ 40.0 $ 5.6 $ 68.4 $ 68.4 Total Net property, plant and equipment costs $ 25.7 $ 32.6 $ 9.7 $ 151.2 $ 151.2 Severance and other employee costs 49.6 60.5 9.9 174.7 174.7 Equipment and inventory relocation costs 3.6 5.8 5.8 17.7 18.2 Facility carrying costs 2.6 4.1 4.2 23.0 25.1 Other costs 12.2 8.0 9.9 36.4 36.7 Restructuring total $ 93.7 $ 111.0 $ 39.5 $ 403.0 $ 405.9
Schedule of Acquisition, Divestiture and Integration Costs	The following table presents our acquisition, integration and divestiture costs that we incurred during the last three fiscal years (in millions): 2020 2019 2018 Acquisition costs $ 0.2 $ 28.2 $ 38.2 Integration costs 18.7 34.3 27.4 Divestiture costs 0.1 0.2 0.3 Other total $ 19.0 $ 62.7 $ 65.9
Schedule of Changes in Restructuring Accrual and Reconciliation of Accrual Charges	The following table summarizes the changes in the restructuring accrual, which is primarily composed of 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 income for the last three fiscal years (in millions): 2020 2019 2018 Accrual at beginning of fiscal year $ 32.3 $ 31.6 $ 47.4 Additional accruals 51.3 60.0 16.5 Payments (56.6 ) (55.9 ) (29.8 ) Adjustment to accruals (6.2 ) (3.2 ) (1.0 ) Foreign currency rate changes and other (3.6 ) (0.2 ) (1.5 ) Accrual at end of fiscal year $ 17.2 $ 32.3 $ 31.6 Reconciliation of accruals and charges to restructuring and other costs (in millions): 2020 2019 2018 Additional accruals and adjustments to accruals (see table above) $ 45.1 $ 56.8 $ 15.5 Acquisition costs 0.2 28.2 38.2 Integration costs 18.7 34.3 22.0 Divestiture costs 0.1 0.2 0.3 Net property, plant and equipment 25.7 32.6 9.7 Severance and other employee costs 1.6 6.8 1.3 Equipment and inventory relocation costs 3.6 5.8 5.8 Facility carrying costs 2.6 4.1 4.2 Other costs (1) 15.1 4.9 8.4 Total restructuring and other costs, net $ 112.7 $ 173.7 $ 105.4 (1)

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Sep. 30, 2020
Retirement Plans [Abstract]
Schedule of Allocation of Plan Assets	Our target asset allocations by asset category at September 30 were as follows: Pension Plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Equity investments 19 % 20 % 15 % 20 % Fixed income investments 75 % 72 % 75 % 72 % Short-term investments 1 % 2 % 1 % 1 % Other investments 5 % 6 % 9 % 7 % Total 100 % 100 % 100 % 100 % Our asset allocations by asset category at September 30 were as follows: Pension Plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Equity investments 22 % 21 % 13 % 22 % Fixed income investments 72 % 72 % 70 % 71 % Short-term investments 3 % 2 % 9 % 2 % Other investments 3 % 5 % 8 % 5 % 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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.01 % 2.16 % 3.35 % 2.42 % Rate of compensation increase 2.50 % 2.68 % 3.00 % 2.65 % Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Pension Plans 2020 2019 2018 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.35 % 2.42 % 4.50 % 3.42 % 4.09 % 3.26 % Rate of compensation increase 3.00 % 2.65 % 3.00 % 2.67 % 3.00 % 2.65 % Expected long-term rate of return on plan assets 6.25 % 4.26 % 6.50 % 4.69 % 6.50 % 4.98 % The weighted average assumptions used to measure the benefit plan obligations at September 30 were: Postretirement plans 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.00 % 4.84 % 3.34 % 5.64 % Weighted-average assumptions used in the calculation of benefit plan expense for fiscal years ended: Postretirement Plans 2020 2019 2018 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Discount rate 3.34 % 5.64 % 4.50 % 6.61 % 4.09 % 6.51 % Rate of compensation increase N/A N/A N/A N/A N/A 7.37 %
Schedule of Changes in Benefit Obligations	The following table shows the changes in benefit obligation, plan assets and funded status for the years ended September 30 (in millions): Pension Plans 2020 2019 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 $ 5,048.9 $ 1,443.1 $ 3,783.5 $ 1,340.2 Service cost 44.2 8.4 36.0 6.8 Interest cost 165.0 33.6 189.2 43.4 Amendments 25.2 (0.2 ) 0.4 3.1 Actuarial loss 214.3 41.9 694.4 181.0 Plan participant contributions — 2.0 — 2.2 Benefits paid (233.1 ) (72.0 ) (216.8 ) (78.3 ) Business combinations — — 561.2 0.7 Curtailments — 3.2 1.0 — Settlements — (9.0 ) — (1.7 ) Foreign currency rate changes — 20.5 — (54.3 ) Benefit obligation at end of fiscal year $ 5,264.5 $ 1,471.5 $ 5,048.9 $ 1,443.1 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ 5,005.3 $ 1,400.9 $ 3,921.2 $ 1,350.2 Actual gain on plan assets 582.6 65.4 731.7 172.9 Employer contributions 14.9 7.6 13.0 12.1 Plan participant contributions — 2.0 — 2.2 Benefits paid (233.1 ) (72.0 ) (216.8 ) (78.3 ) Business combinations — — 556.2 — Settlements — (9.0 ) — (1.7 ) Foreign currency rate changes — 23.1 — (56.5 ) Fair value of plan assets at end of fiscal year $ 5,369.7 $ 1,418.0 $ 5,005.3 $ 1,400.9 Funded status $ 105.2 $ (53.5 ) $ (43.6 ) $ (42.2 ) Amounts recognized in the consolidated balance sheet: Prepaid pension asset $ 290.6 $ 78.1 $ 143.3 $ 81.4 Other current liabilities (10.7 ) (1.1 ) (14.6 ) (1.9 ) Pension liabilities, net of current portion (174.7 ) (130.5 ) (172.3 ) (121.7 ) Over (under) funded status at end of fiscal year $ 105.2 $ (53.5 ) $ (43.6 ) $ (42.2 ) The following table shows the changes in benefit obligation, plan assets and funded status for the fiscal years ended September 30 (in millions): Postretirement Plans 2020 2019 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 $ 98.3 $ 75.7 $ 91.0 $ 55.5 Service cost 0.6 0.7 0.7 0.5 Interest cost 3.2 3.7 4.1 3.6 Amendments (0.1 ) 2.0 0.4 — Actuarial (gain) loss (3.1 ) (5.3 ) 1.6 22.2 Benefits paid (5.3 ) (2.9 ) (6.6 ) (2.9 ) Business combinations — — 7.1 — Foreign currency rate changes — (11.4 ) — (3.2 ) Benefit obligation at end of fiscal year $ 93.6 $ 62.5 $ 98.3 $ 75.7 Change in plan assets: Fair value of plan assets at beginning of fiscal year $ — $ — $ — $ — Employer contributions 5.3 2.9 6.6 2.9 Benefits paid (5.3 ) (2.9 ) (6.6 ) (2.9 ) Fair value of plan assets at end of fiscal year $ — $ — $ — $ — Funded Status $ (93.6 ) $ (62.5 ) $ (98.3 ) $ (75.7 ) Amounts recognized in the consolidated balance sheet: Other current liabilities $ (8.0 ) $ (2.7 ) $ (8.9 ) $ (3.0 ) Postretirement benefit liabilities, net of current portion (85.6 ) (59.8 ) (89.4 ) (72.7 ) Under funded status at end of fiscal year $ (93.6 ) $ (62.5 ) $ (98.3 ) $ (75.7 )
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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial loss $ 753.2 $ 188.6 $ 854.7 $ 168.8 Prior service cost 45.6 2.4 27.6 3.4 Total accumulated other comprehensive loss $ 798.8 $ 191.0 $ 882.3 $ 172.2 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 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans Net actuarial (gain) loss $ (10.6 ) $ 13.0 $ (8.0 ) $ 18.8 Prior service (credit) cost (5.7 ) 1.2 (8.3 ) (0.9 ) Total accumulated other comprehensive (income) loss $ (16.3 ) $ 14.2 $ (16.3 ) $ 17.9
Schedule of Amounts Recognized in Other Comprehensive Loss (Income)	The pre-tax amounts recognized in other comprehensive loss (income), including noncontrolling interest, are as follows at September 30 (in millions): Pension Plans 2020 2019 2018 Net actuarial (gain) loss arising during period $ (26.2 ) $ 312.0 $ 38.7 Amortization and settlement recognition of net actuarial loss (48.2 ) (25.3 ) (20.6 ) Prior service cost arising during period 25.0 3.5 9.3 Amortization of prior service cost (7.8 ) (5.2 ) (4.7 ) Net other comprehensive (income) loss recognized $ (57.2 ) $ 285.0 $ 22.7 The pre-tax amounts recognized in other comprehensive loss (income), including noncontrolling interest, are as follows at September 30 (in millions): Postretirement Plans 2020 2019 2018 Net actuarial (gain) loss arising during period $ (8.4 ) $ 23.9 $ (9.7 ) Amortization and settlement recognition of net actuarial (loss) gain (0.1 ) 2.0 (0.3 ) Prior service cost (credit) arising during period 1.9 0.4 (1.5 ) Amortization or curtailment recognition of prior service credit 2.7 2.8 4.4 Net other comprehensive (income) loss recognized $ (3.9 ) $ 29.1 $ (7.1 )
Summary of Components of Net Pension Income and Summary of Components of Postretirement Benefit Cost	The net periodic pension (income) cost recognized in the consolidated statements of operations is comprised of the following for fiscal years ended (in millions): Pension Plans 2020 2019 2018 Service cost $ 52.6 $ 42.8 $ 44.8 Interest cost 198.6 232.6 204.6 Expected return on plan assets (362.3 ) (340.2 ) (328.4 ) Amortization of net actuarial loss 46.8 24.5 21.2 Amortization of prior service cost 7.5 5.2 4.7 Curtailment loss (gain) 0.4 1.0 (0.6 ) Settlement loss (gain) 1.4 (0.2 ) (0.5 ) Company defined benefit plan (income) cost (55.0 ) (34.3 ) (54.2 ) Multiemployer and other plans 2.0 1.4 1.4 Net pension (income) cost $ (53.0 ) $ (32.9 ) $ (52.8 ) 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 2020 2019 2018 Service cost $ 1.3 $ 1.2 $ 1.5 Interest cost 6.9 7.7 7.9 Amortization of net actuarial loss (gain) 0.1 (2.0 ) 0.3 Amortization of prior service credit (2.7 ) (2.8 ) (4.4 ) Curtailment gain — — (0.1 ) Net postretirement cost $ 5.6 $ 4.1 $ 5.2
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 2021 are as follows (in millions): Pension Plans U.S. Plans Non-U.S. Plans Actuarial loss $ 20.9 $ 10.4 Prior service cost 7.8 0.2 Total $ 28.7 $ 10.6 The estimated gains that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in fiscal 2021 are as follows (in millions): Postretirement Plans U.S. Plans Non-U.S. Plans Actuarial (gain) loss $ (1.3 ) $ 0.1 Prior service (credit) cost (2.5 ) 0.1 Total $ (3.8 ) $ 0.2
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 2021 $ 264.6 $ 71.9 Fiscal 2022 $ 273.5 $ 71.5 Fiscal 2023 $ 277.6 $ 71.7 Fiscal 2024 $ 282.0 $ 71.0 Fiscal 2025 $ 278.0 $ 71.3 Fiscal Years 2026 – 2030 $ 1,422.0 $ 350.0 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 2021 $ 8.6 $ 2.7 Fiscal 2022 $ 7.6 $ 2.7 Fiscal 2023 $ 7.2 $ 2.8 Fiscal 2024 $ 6.9 $ 2.9 Fiscal 2025 $ 6.6 $ 3.0 Fiscal Years 2026 – 2030 $ 29.2 $ 16.7
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, 2020 (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) $ 253.0 $ 253.0 $ — Non-U.S. equities (1) 4.0 4.0 — Fixed income securities: U.S. government securities (2) 331.7 — 331.7 Non-U.S. government securities (3) 103.1 — 103.1 U.S. corporate bonds (3) 2,875.3 124.9 2,750.4 Non-U.S. corporate bonds (3) 540.7 — 540.7 Other fixed income (4) 388.0 — 388.0 Short-term investments (5) 168.7 168.7 — Benefit plan assets measured in the fair value hierarchy $ 4,664.5 $ 550.6 $ 4,113.9 Assets measured at NAV (6) 2,123.2 Total benefit plan assets $ 6,787.7 The following table summarizes our pension plan assets measured at fair value on a recurring basis (at least annually) as of September 30, 2019 (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) $ 184.2 $ 183.5 $ 0.7 Non-U.S. equities (1) 6.5 6.5 — Fixed income securities: U.S. government securities (2) 598.2 — 598.2 Non-U.S. government securities (3) 125.6 0.2 125.4 U.S. corporate bonds (3) 2,156.0 137.6 2,018.4 Non-U.S. corporate bonds (3) 432.9 5.7 427.2 Other fixed income (4) 379.3 10.8 368.5 Short-term investments (5) 468.7 468.7 — Benefit plan assets measured in the fair value hierarchy $ 4,351.4 $ 813.0 $ 3,538.4 Assets measured at NAV (6) 2,054.8 Total benefit plan assets $ 6,406.2 (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 cleared swap 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) Investments that are measured at net asset value (“ 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, 2020 and 2019 (in millions): Fair value Redemption Frequency Redemption Notice Period Unfunded Commitments September 30, 2020 Hedge funds (1) $ 39.2 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,416.9 Monthly Up to 60 days 228.9 Fixed income and fixed income related instruments (3) 667.1 Monthly Up to 10 days — $ 2,123.2 $ 228.9 September 30, 2019 Hedge funds (1) $ 42.9 Monthly Up to 30 days $ — Commingled funds, private equity, private real estate investments, and equity related investments (2) 1,188.6 Monthly Up to 60 days 113.1 Fixed income and fixed income related instruments (3) 823.3 Monthly Up to 10 days — $ 2,054.8 $ 113.1 (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. (2) Commingled fund investments are valued at the NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques. (3) Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques.
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 5.57 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.42 % Year the rate reaches the ultimate trend rate 2038 Non-U.S. Plans Health care cost trend rate assumed for next year 5.25 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.25 % Year the rate reaches the ultimate trend rate 2020

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Schedule of (Loss) Income before Income Tax, Domestic and Foreign	The components of (loss) income before income taxes are as follows (in millions): Year Ended September 30, 2020 2019 2018 United States $ (440.7 ) $ 891.6 $ 736.7 Foreign (81.9 ) 253.1 298.1 Income before income taxes $ (522.6 ) $ 1,144.7 $ 1,034.8
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense (benefit) consists of the following components (in millions): Year Ended September 30, 2020 2019 2018 Current income taxes: Federal $ 31.6 $ 134.7 $ 83.0 State 23.5 34.9 26.8 Foreign 66.8 69.5 86.6 Total current expense 121.9 239.1 196.4 Deferred income taxes: Federal 42.4 44.1 (1,108.6 ) State 6.2 6.1 53.2 Foreign (7.0 ) (12.5 ) (15.5 ) Total deferred expense (benefit) 41.6 37.7 (1,070.9 ) Total income tax expense (benefit) $ 163.5 $ 276.8 $ (874.5 )
Schedule of Effective Income Tax Rate Reconciliation	The differences between the statutory federal income tax rate and our effective income tax rate are as follows: Year Ended September 30, 2020 (1) 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 24.5 % Foreign rate differential (1.1 ) 1.3 0.6 Adjustment and resolution of federal, state and foreign tax uncertainties 2.7 1.2 0.9 State taxes, net of federal benefit (1.3 ) 2.5 4.3 Tax Act (2) — — (109.1 ) Excess tax benefit related to stock compensation (0.5 ) (0.3 ) (0.8 ) Research and development and other tax credits, net of valuation allowances and reserves 3.7 (0.7 ) (0.5 ) Income attributable to noncontrolling interest 0.1 (0.1 ) (0.1 ) Domestic manufacturer’s deduction — — (1.8 ) Change in valuation allowance (4.1 ) 0.2 (1.8 ) Nondeductible transaction costs — 1.0 — Goodwill impairment (51.2 ) — — Nontaxable increased cash surrender value 1.3 (0.6 ) (0.8 ) Withholding taxes (0.7 ) 0.6 0.5 Brazilian net worth deduction 1.7 (0.9 ) (0.9 ) Other, net (2.9 ) (1.0 ) 0.5 Effective tax rate (31.3 )% 24.2 % (84.5 )% (1) The negative tax rate for fiscal year 2020 is the result of applying total income tax expense to the loss before income taxes. The signs within the table are consequently the opposite compared to prior year. (2) For the year ended September 30, 2018, 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.
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, 2020 2019 Deferred income tax assets: Accruals and allowances $ 5.3 $ 10.7 Employee related accruals and allowances 121.3 125.1 Pension 60.5 96.8 State net operating loss carryforwards, net of federal benefit 67.0 57.6 State credit carryforwards, net of federal benefit 79.4 69.5 Federal and foreign net operating loss carryforwards 188.3 173.5 Restricted stock and options 33.7 39.3 Lease liabilities 179.1 — Other 52.8 52.8 Total 787.4 625.3 Deferred income tax liabilities: Property, plant and equipment 1,885.5 1,840.5 Deductible intangibles and goodwill 841.5 914.7 Inventory reserves 216.2 188.3 Deferred gain 272.2 275.2 Basis difference in joint ventures 33.8 33.1 Right-of-use assets 163.8 — Total 3,413.0 3,251.8 Valuation allowances 257.5 218.0 Net deferred income tax liability $ 2,883.1 $ 2,844.5
Location Of Deferred Taxes In Balance Sheet	Deferred taxes are recorded as follows in the consolidated balance sheet (in millions): September 30, 2020 2019 Long-term deferred tax asset (1) $ 33.8 $ 33.5 Long-term deferred tax liability 2,916.9 2,878.0 Net deferred income tax liability $ 2,883.1 $ 2,844.5 (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 2020, 2019 and 2018 (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 218.0 $ 229.4 $ 219.1 Increases 46.2 25.4 50.8 Allowances related to purchase accounting (1) — 0.8 0.1 Reductions (6.7 ) (37.6 ) (40.6 ) Balance at end of fiscal year $ 257.5 $ 218.0 $ 229.4 (1) Amounts in fiscal 2019 relate to the KapStone Acquisition. Amounts in fiscal 2018 relate to the MPS Acquisition.
Summary of Income Tax Contingencies	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in millions): 2020 2019 2018 Balance at beginning of fiscal year $ 224.3 $ 127.1 $ 148.9 Additions related to purchase accounting (1) — 1.0 3.4 Additions for tax positions taken in current year (2) 5.0 103.8 3.1 Additions for tax positions taken in prior fiscal years 11.7 1.8 18.0 Reductions for tax positions taken in prior fiscal years (2) (16.7 ) (0.5 ) (5.3 ) Reductions due to settlement (3) — (4.0 ) (29.4 ) Reductions for currency translation adjustments (8.8 ) (1.7 ) (9.6 ) Reductions as a result of a lapse of the applicable statute of limitations (8.8 ) (3.2 ) (2.0 ) Balance at end of fiscal year $ 206.7 $ 224.3 $ 127.1 (1) (2) (3) Amounts in fiscal 2019 relate to the settlements of state and foreign audit examinations. 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 there was a reserve.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Sep. 30, 2020
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, 2020 2019 2018 Foreign net sales to unaffiliated customers $ 3,105.6 $ 3,332.4 $ 3,236.7 Foreign segment income $ 298.2 $ 392.3 $ 360.7 Foreign long-lived assets $ 1,390.6 $ 1,466.4 $ 1,400.2 Foreign operations as a percent of consolidated operations: Foreign net sales to unaffiliated customers 17.7 % 18.2 % 19.9 % Foreign segment income 21.9 % 21.9 % 21.1 % Foreign long-lived assets 12.9 % 13.1 % 15.4 %
Certain Operating Data for Segments	The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2020 2019 2018 Net sales (aggregate): Corrugated Packaging $ 11,419.2 $ 11,816.7 $ 9,693.0 Consumer Packaging 6,333.0 6,606.0 6,617.5 Land and Development 18.9 23.4 142.4 Total $ 17,771.1 $ 18,446.1 $ 16,452.9 Less net sales (intersegment): Corrugated Packaging $ 71.0 $ 75.3 $ 87.3 Consumer Packaging 121.3 81.8 80.5 Total $ 192.3 $ 157.1 $ 167.8 Net sales (unaffiliated customers): Corrugated Packaging $ 11,348.2 $ 11,741.4 $ 9,605.7 Consumer Packaging 6,211.7 6,524.2 6,537.0 Land and Development 18.9 23.4 142.4 Total $ 17,578.8 $ 18,289.0 $ 16,285.1 Segment income: Corrugated Packaging $ 1,037.7 $ 1,399.6 $ 1,240.0 Consumer Packaging 323.7 388.1 445.1 Land and Development 1.4 2.5 22.5 Segment income 1,362.8 1,790.2 1,707.6 Gain on sale of certain closed facilities 15.6 52.6 — Multiemployer pension withdrawal income (expense) 1.1 6.3 (184.2 ) Land and Development impairments — (13.0 ) (31.9 ) Restructuring and other costs (112.7 ) (173.7 ) (105.4 ) Goodwill impairment (1,333.2 ) — — Non-allocated expenses (70.7 ) (83.7 ) (70.1 ) Interest expense, net (393.5 ) (431.3 ) (293.8 ) Loss on extinguishment of debt (1.5 ) (5.1 ) (0.1 ) Other income, net 9.5 2.4 12.7 (Loss) income before income taxes $ (522.6 ) $ 1,144.7 $ 1,034.8 Years Ended September 30, 2020 2019 2018 Depreciation and amortization: Corrugated Packaging $ 951.4 $ 950.6 $ 700.5 Consumer Packaging 529.5 552.1 546.5 Land and Development — — 0.7 Corporate 6.1 8.5 4.5 Total $ 1,487.0 $ 1,511.2 $ 1,252.2 The following table shows selected operating data for our segments (in millions): Years Ended September 30, 2020 2019 2018 Identifiable assets: Corrugated Packaging $ 16,507.0 $ 16,681.1 $ 11,069.6 Consumer Packaging 9,584.9 11,038.7 11,511.1 Land and Development — 28.3 49.1 Assets held for sale 7.0 25.8 59.5 Corporate 2,680.8 2,382.8 2,671.2 Total $ 28,779.7 $ 30,156.7 $ 25,360.5 Goodwill: Corrugated Packaging $ 3,673.5 $ 3,695.0 $ 1,966.7 Consumer Packaging 2,288.7 3,590.6 3,610.9 Total $ 5,962.2 $ 7,285.6 $ 5,577.6 Intangibles, net: Corrugated Packaging $ 1,423.0 $ 1,655.1 $ 506.2 Consumer Packaging 2,244.2 2,404.4 2,615.8 Total $ 3,667.2 $ 4,059.5 $ 3,122.0 Capital expenditures: Corrugated Packaging $ 731.1 $ 961.4 $ 657.3 Consumer Packaging 217.1 365.9 308.3 Corporate 29.9 41.8 34.3 Total $ 978.1 $ 1,369.1 $ 999.9 Equity method investments: Corrugated Packaging $ 414.3 $ 457.1 $ 455.6 Consumer Packaging 14.9 11.6 1.8 Corporate 0.4 0.4 0.4 Total $ 429.6 $ 469.1 $ 457.8
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the fiscal years ended September 30, 2020, 2019 and 2018 are as follows (in millions): Corrugated Packaging Consumer Packaging Total Balance as of October 1, 2017 Goodwill $ 1,941.6 $ 3,629.5 $ 5,571.1 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 1,941.5 3,586.8 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 1,966.8 3,653.6 5,620.4 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 1,966.7 3,610.9 5,577.6 Goodwill acquired 1,746.4 3.8 1,750.2 Purchase price allocation adjustments 0.9 (1.4 ) (0.5 ) Translation and other adjustments (19.0 ) (22.7 ) (41.7 ) Balance as of September 30, 2019 Goodwill 3,695.1 3,633.3 7,328.4 Accumulated impairment losses (0.1 ) (42.7 ) (42.8 ) 3,695.0 3,590.6 7,285.6 Goodwill impairment — (1,333.2 ) (1,333.2 ) Goodwill disposed of — (0.3 ) (0.3 ) Purchase price allocation adjustments 14.3 (0.6 ) 13.7 Translation adjustments (35.8 ) 32.2 (3.6 ) Balance as of September 30, 2020 Goodwill 3,673.6 3,664.6 7,338.2 Accumulated impairment losses (0.1 ) (1,375.9 ) (1,376.0 ) $ 3,673.5 $ 2,288.7 $ 5,962.2

Interest Expense, Net (Tables)

Interest Expense, Net (Tables)	12 Months Ended
	Sep. 30, 2020
Interest Income Expense Net [Abstract]
Summary of Components of Interest Expense, Net	The components of interest expense, net is as follows (in millions): Years Ended September 30, 2020 2019 2018 Interest expense $ (465.5 ) $ (489.4 ) $ (352.8 ) Interest income 72.0 58.1 59.0 Interest expense, net $ (393.5 ) $ (431.3 ) $ (293.8 )

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories are as follows (in millions): September 30, 2020 2019 Finished goods and work in process $ 844.2 $ 938.9 Raw materials 772.7 818.8 Supplies and spare parts 500.3 479.7 Inventories at FIFO cost 2,117.2 2,237.4 LIFO reserve (93.8 ) (129.9 ) Net inventories $ 2,023.4 $ 2,107.5

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment consists of the following (in millions): September 30, 2020 2019 Property, plant and equipment at cost: Land and buildings $ 2,524.7 $ 2,442.3 Machinery and equipment 15,147.3 14,743.6 Forestlands and mineral rights 110.8 144.0 Transportation equipment 29.1 31.2 Leasehold improvements 103.6 100.2 17,915.5 17,461.3 Less: accumulated depreciation, depletion and amortization (7,136.6 ) (6,271.8 ) Property, plant and equipment, net $ 10,778.9 $ 11,189.5

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2020
Other Intangible Assets [Abstract]
Schedule of Finite-Lived Intangible Assets	The gross carrying amount and accumulated amortization relating to intangible assets, excluding goodwill, are as follows (in millions, except weighted avg. life): September 30, 2020 2019 Weighted Avg. Life (in years) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships 15.5 $ 5,418.1 $ (1,841.2 ) $ 5,395.5 $ (1,452.1 ) Trademarks and tradenames 21.6 130.5 (65.7 ) 129.9 (55.3 ) Favorable contracts 7.2 44.0 (41.6 ) 57.0 (42.6 ) Technology and patents 11.4 37.5 (21.6 ) 39.2 (21.2 ) License costs 8.0 26.5 (22.8 ) 25.7 (20.5 ) Non-compete agreements 2.0 3.4 (3.3 ) 3.4 (2.9 ) Other 29.5 3.7 (0.3 ) 3.6 (0.2 ) Total 15.5 $ 5,663.7 $ (1,996.5 ) $ 5,654.3 $ (1,594.8 )
Estimated intangible asset future amortization expense	Estimated intangible asset amortization expense for the succeeding five fiscal years is as follows (in millions): Fiscal 2021 $ 356.8 Fiscal 2022 $ 349.3 Fiscal 2023 $ 343.1 Fiscal 2024 $ 322.6 Fiscal 2025 $ 308.0

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Sep. 30, 2020
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 for fiscal 2020 and 2019 (in millions): 2020 2019 Receivable from financial institution at beginning of fiscal year $ — $ — Receivables sold to the financial institution and derecognized 2,446.2 2,051.6 Receivables collected by financial institution (2,449.4 ) (1,971.1 ) Cash proceeds from financial institution 3.2 (80.5 ) Receivable from financial institution at September 30, $ — $ —

Debt (Tables)

Debt (Tables)	12 Months Ended
	Sep. 30, 2020
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, 2020 September 30, 2019 Carrying Value Weighted Avg Interest Rate Carrying Value Weighted Avg Interest Rate Public bonds due fiscal 2020 to 2022 $ 399.3 5.0 % $ 507.8 4.9 % Public bonds due fiscal 2023 to 2028 3,773.6 4.0 % 3,769.1 4.0 % Public bonds due fiscal 2029 to 2033 2,778.9 4.5 % 2,197.6 4.9 % Public bonds due fiscal 2037 to 2047 178.6 6.2 % 179.0 6.2 % Term loan facilities 1,547.6 1.9 % 2,295.5 3.3 % Revolving credit and swing facilities 250.0 1.1 % 396.0 2.9 % Commercial paper — N/A 339.2 2.4 % Finance lease obligations 274.8 4.0 % 185.8 4.3 % Vendor financing and commercial card programs 89.8 N/A 123.2 N/A International and other debt 138.0 3.1 % 70.2 6.6 % Total debt 9,430.6 3.8 % 10,063.4 4.0 % Less: current portion of debt 222.9 561.1 Long-term debt due after one year $ 9,207.7 $ 9,502.3
Schedule of aggregate maturities of debt	As of September 30, 2020, the aggregate maturities of debt, excluding finance lease obligations, for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2021 $ 214.2 Fiscal 2022 438.7 Fiscal 2023 639.1 Fiscal 2024 1,386.8 Fiscal 2025 600.0 Thereafter 5,729.1 Fair value of debt step-up, deferred financing costs and unamortized bond discounts 147.9 Total $ 9,155.8

Selected Condensed Consolidat_2

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors (Tables)	12 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Condensed Consolidating Statements of Operations	CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,430.9 $ 17,740.7 $ (2,592.8 ) $ 17,578.8 Cost of goods sold — — 1,916.7 15,026.1 (2,561.2 ) 14,381.6 Gross profit — — 514.2 2,714.6 (31.6 ) 3,197.2 Selling, general and administrative, excluding intangible amortization — 2.8 101.2 1,520.4 — 1,624.4 Selling, general and administrative intangible amortization — — 99.5 301.0 — 400.5 Gain on disposal of assets — — (0.1 ) (16.2 ) — (16.3 ) Multiemployer pension withdrawal (income) expense — — (1.9 ) 0.8 — (1.1 ) Restructuring and other costs — 4.6 — 108.1 — 112.7 Goodwill impairment — — 746.9 586.3 — 1,333.2 Operating (loss) profit — (7.4 ) (431.4 ) 214.2 (31.6 ) (256.2 ) Interest expense, net — (250.1 ) (137.9 ) (5.5 ) — (393.5 ) Intercompany interest (expense) income, net — (10.2 ) (80.7 ) 59.3 31.6 — Loss on extinguishment of debt — (1.4 ) — (0.1 ) — (1.5 ) Pension and other postretirement non-service (expense) income — — (6.9 ) 110.2 — 103.3 Other income (expense), net 0.1 0.2 (82.6 ) 91.8 — 9.5 Equity in income of unconsolidated entities — — — 15.8 — 15.8 Equity in (loss) income of consolidated entities (691.0 ) (343.2 ) 228.6 — 805.6 — (Loss) income before income taxes (690.9 ) (612.1 ) (510.9 ) 485.7 805.6 (522.6 ) Income tax benefit (expense) — 77.7 11.4 (252.6 ) — (163.5 ) Consolidated net (loss) income (690.9 ) (534.4 ) (499.5 ) 233.1 805.6 (686.1 ) Less: Net income attributable to noncontrolling interests — — — (4.8 ) — (4.8 ) Net (loss) income attributable to common stockholders $ (690.9 ) $ (534.4 ) $ (499.5 ) $ 228.3 $ 805.6 $ (690.9 ) Comprehensive (loss) income attributable to common stockholders $ (868.2 ) $ (711.0 ) $ (677.1 ) $ 51.4 $ 1,336.7 $ (868.2 ) CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,543.8 $ 18,364.4 $ (2,619.2 ) $ 18,289.0 Cost of goods sold — — 2,026.0 15,114.2 (2,600.2 ) 14,540.0 Gross profit — — 517.8 3,250.2 (19.0 ) 3,749.0 Selling, general and administrative, excluding intangible amortization — (0.9 ) 120.0 1,596.1 — 1,715.2 Selling, general and administrative intangible amortization — — 104.4 295.8 — 400.2 Loss (gain) on disposal of assets — — 0.1 (41.3 ) — (41.2 ) Multiemployer pension withdrawal income — (0.2 ) (0.3 ) (5.8 ) — (6.3 ) Land and Development impairments — — — 13.0 — 13.0 Restructuring and other costs — 7.6 0.3 165.8 — 173.7 Operating profit (loss) — (6.5 ) 293.3 1,226.6 (19.0 ) 1,494.4 Interest expense, net — (246.8 ) (163.4 ) (21.1 ) — (431.3 ) Intercompany interest (expense) income, net — (3.2 ) (115.3 ) 99.5 19.0 — Loss on extinguishment of debt — (3.0 ) (1.9 ) (0.2 ) — (5.1 ) Pension and other postretirement non-service (expense) income — — (6.5 ) 80.7 — 74.2 Other (expense) income, net — (5.1 ) 3.4 4.1 — 2.4 Equity in income of unconsolidated entities — — — 10.1 — 10.1 Equity in income of consolidated entities 862.9 1,157.3 736.5 — (2,756.7 ) — Income before income taxes 862.9 892.7 746.1 1,399.7 (2,756.7 ) 1,144.7 Income tax benefit (expense) — 67.9 7.2 (351.9 ) — (276.8 ) Consolidated net income 862.9 960.6 753.3 1,047.8 (2,756.7 ) 867.9 Less: Net income attributable to noncontrolling interests — — — (5.0 ) — (5.0 ) Net income attributable to common stockholders $ 862.9 $ 960.6 $ 753.3 $ 1,042.8 $ (2,756.7 ) $ 862.9 Comprehensive income attributable to common stockholders $ 489.0 $ 588.0 $ 389.4 $ 682.4 $ (1,659.8 ) $ 489.0 CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Net sales $ — $ — $ 2,593.0 $ 16,345.4 $ (2,653.3 ) $ 16,285.1 Cost of goods sold — — 2,004.2 13,572.2 (2,653.3 ) 12,923.1 Gross profit — — 588.8 2,773.2 — 3,362.0 Selling, general and administrative, excluding intangible amortization — 1.5 94.1 1,451.0 — 1,546.6 Selling, general and administrative intangible amortization — — 104.2 192.4 — 296.6 Loss on disposal of assets — — 0.2 9.9 — 10.1 Multiemployer pension withdrawals — 6.5 12.5 165.2 — 184.2 Land and Development impairments — — — 31.9 — 31.9 Restructuring and other costs — 8.7 5.6 91.1 — 105.4 Operating profit (loss) — (16.7 ) 372.2 831.7 — 1,187.2 Interest expense, net (12.5 ) (76.9 ) (173.5 ) (30.9 ) — (293.8 ) Intercompany interest income (expense), net — 28.1 (87.6 ) 59.5 — — (Loss) gain on extinguishment of debt (0.2 ) (1.4 ) 1.9 (0.4 ) — (0.1 ) Pension and other postretirement non-service (expense) income — — (6.9 ) 102.2 — 95.3 Other income (expense), net — 0.7 (22.5 ) 34.5 — 12.7 Equity in income of unconsolidated entities — — 7.5 26.0 — 33.5 Equity in income of consolidated entities — 1,962.0 1,343.8 — (3,305.8 ) — Income (loss) before income taxes (12.7 ) 1,895.8 1,434.9 1,022.6 (3,305.8 ) 1,034.8 Income tax benefit 3.1 19.9 131.8 719.7 — 874.5 Consolidated net income (loss) (9.6 ) 1,915.7 1,566.7 1,742.3 (3,305.8 ) 1,909.3 Less: Net income attributable to noncontrolling interests — — — (3.2 ) — (3.2 ) Net income (loss) attributable to common stockholders $ (9.6 ) $ 1,915.7 $ 1,566.7 $ 1,739.1 $ (3,305.8 ) $ 1,906.1 Comprehensive income (loss) attributable to common stockholders $ (9.6 ) $ 1,677.7 $ 1,351.4 $ 1,498.6 $ (2,850.0 ) $ 1,668.1
Condensed Consolidating Balance Sheets	CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total ASSETS Current assets: Cash and cash equivalents $ — $ — $ 105.7 $ 145.4 $ — $ 251.1 Accounts receivable — — 41.6 2,152.0 (50.9 ) 2,142.7 Inventories — — 175.3 1,848.1 — 2,023.4 Other current assets 0.5 — 11.6 508.4 — 520.5 Intercompany receivables — 3.0 1.5 1,798.6 (1,803.1 ) — Assets held for sale — — — 7.0 — 7.0 Total current assets 0.5 3.0 335.7 6,459.5 (1,854.0 ) 4,944.7 Property, plant and equipment, net — — 15.2 10,763.7 — 10,778.9 Goodwill — — 411.7 5,550.5 — 5,962.2 Intangibles, net — — 1,385.5 2,281.7 — 3,667.2 Restricted assets held by special purpose entities — — — 1,267.5 — 1,267.5 Prepaid pension asset — — — 368.7 — 368.7 Intercompany notes receivable — 168.8 141.1 2,821.3 (3,131.2 ) — Investments in consolidated subsidiaries 11,070.4 17,829.4 19,685.2 — (48,585.0 ) — Other assets — 63.6 220.8 1,565.5 (59.4 ) 1,790.5 Total assets $ 11,070.9 $ 18,064.8 $ 22,195.2 $ 31,078.4 $ (53,629.6 ) $ 28,779.7 LIABILITIES AND EQUITY Current liabilities: Current portion of debt $ — $ 99.8 $ — $ 123.1 $ — $ 222.9 Accounts payable — 1.9 27.7 1,695.5 (50.9 ) 1,674.2 Accrued compensation and benefits 0.1 — 10.2 376.4 — 386.7 Other current liabilities — 27.1 71.0 547.0 — 645.1 Intercompany payables 440.2 643.6 440.8 278.5 (1,803.1 ) — Total current liabilities 440.3 772.4 549.7 3,020.5 (1,854.0 ) 2,928.9 Long-term debt due after one year — 6,108.3 1,968.3 1,131.1 — 9,207.7 Intercompany notes payable — 753.3 2,068.0 309.9 (3,131.2 ) — Pension liabilities, net of current portion — — 149.7 155.5 — 305.2 Postretirement benefit liabilities, net of current portion — — 25.9 119.5 — 145.4 Non-recourse liabilities held by special purpose entities — — — 1,136.5 — 1,136.5 Deferred income taxes — — 221.1 2,755.2 (59.4 ) 2,916.9 Other long-term liabilities — 13.0 147.1 1,330.2 — 1,490.3 Redeemable noncontrolling interests — — — 1.3 — 1.3 Total stockholders’ equity 10,630.6 10,417.8 17,065.4 21,101.8 (48,585.0 ) 10,630.6 Noncontrolling interests — — — 16.9 — 16.9 Total equity 10,630.6 10,417.8 17,065.4 21,118.7 (48,585.0 ) 10,647.5 Total liabilities and equity $ 11,070.9 $ 18,064.8 $ 22,195.2 $ 31,078.4 $ (53,629.6 ) $ 28,779.7 CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total ASSETS Current assets: Cash and cash equivalents $ — $ — $ 17.8 $ 133.8 $ — $ 151.6 Accounts receivable — — 31.1 2,201.7 (39.6 ) 2,193.2 Inventories — — 254.3 1,853.2 — 2,107.5 Other current assets — 1.2 11.8 483.2 — 496.2 Intercompany receivables — 227.7 — 1,128.6 (1,356.3 ) — Assets held for sale — — — 25.8 — 25.8 Total current assets — 228.9 315.0 5,826.3 (1,395.9 ) 4,974.3 Property, plant and equipment, net — — 18.9 11,170.6 — 11,189.5 Goodwill — — 1,158.6 6,127.0 — 7,285.6 Intangibles, net — — 1,485.0 2,574.5 — 4,059.5 Restricted assets held by special purpose entities — — — 1,274.3 — 1,274.3 Prepaid pension asset — — — 224.7 — 224.7 Intercompany notes receivable — 155.0 156.9 3,026.8 (3,338.7 ) — Investments in consolidated subsidiaries 11,973.6 18,524.2 20,103.6 — (50,601.4 ) — Other assets — 67.8 185.3 971.8 (76.1 ) 1,148.8 Total assets $ 11,973.6 $ 18,975.9 $ 23,423.3 $ 31,196.0 $ (55,412.1 ) $ 30,156.7 LIABILITIES AND EQUITY Current liabilities: Current portion of debt $ — $ 135.3 $ 108.9 $ 316.9 $ — $ 561.1 Accounts payable — 0.7 31.3 1,839.4 (39.6 ) 1,831.8 Accrued compensation and benefits 0.3 — 14.5 455.6 — 470.4 Other current liabilities — 18.6 83.8 469.4 — 571.8 Intercompany payables 303.4 — 1,052.9 — (1,356.3 ) — Total current liabilities 303.7 154.6 1,291.4 3,081.3 (1,395.9 ) 3,435.1 Long-term debt due after one year — 6,608.0 1,982.9 911.4 — 9,502.3 Intercompany notes payable — 636.3 2,390.5 311.9 (3,338.7 ) — Pension liabilities, net of current portion — — 147.6 146.4 — 294.0 Postretirement benefit liabilities, net of current portion — — 25.7 136.4 — 162.1 Non-recourse liabilities held by special purpose entities — — — 1,145.2 — 1,145.2 Deferred income taxes — — 278.9 2,675.2 (76.1 ) 2,878.0 Other long-term liabilities — 12.9 131.2 909.8 — 1,053.9 Redeemable noncontrolling interests — — — 1.9 — 1.9 Total stockholders’ equity 11,669.9 11,564.1 17,175.1 21,862.2 (50,601.4 ) 11,669.9 Noncontrolling interests — — — 14.3 — 14.3 Total equity 11,669.9 11,564.1 17,175.1 21,876.5 (50,601.4 ) 11,684.2 Total liabilities and equity $ 11,973.6 $ 18,975.9 $ 23,423.3 $ 31,196.0 $ (55,412.1 ) $ 30,156.7
Condensed Consolidating Statements of Cash Flows	CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by operating activities $ 322.3 $ 540.5 $ 171.1 $ 1,036.8 $ — $ 2,070.7 Investing activities: Capital expenditures — — — (978.1 ) — (978.1 ) Investment in unconsolidated entities — — — (1.3 ) — (1.3 ) Proceeds from sale of property, plant and equipment — — 0.1 34.9 — 35.0 Proceeds from property, plant and equipment insurance settlement — 1.5 1.3 3.7 — 6.5 Intercompany notes proceeds — — 5.7 — (5.7 ) — Other — — 14.7 1.7 — 16.4 Net cash provided by (used for) investing activities — 1.5 21.8 (939.1 ) (5.7 ) (921.5 ) Financing activities: Proceeds from issuance of notes — 598.6 — — — 598.6 Additions to revolving credit facilities — 350.0 — 78.0 — 428.0 Repayments of revolving credit facilities — (350.0 ) — (178.2 ) — (528.2 ) Additions to debt — — — 696.4 — 696.4 Repayments of debt — (750.0 ) (105.0 ) (594.2 ) — (1,449.2 ) Changes in commercial paper, net — (339.2 ) — — — (339.2 ) Other financing repayments — (46.0 ) — (34.3 ) — (80.3 ) Issuances of common stock, net of related minimum tax withholdings 22.2 — — — — 22.2 Cash dividends paid to stockholders (344.5 ) — — — — (344.5 ) Cash distributions paid to noncontrolling interests — — — (2.4 ) — (2.4 ) Intercompany notes payments — — — (5.7 ) 5.7 — Other — (5.4 ) — (17.1 ) — (22.5 ) Net cash used for financing activities (322.3 ) (542.0 ) (105.0 ) (57.5 ) 5.7 (1,021.1 ) Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — (28.6 ) — (28.6 ) Increase in cash, cash equivalents and restricted cash — — 87.9 11.6 — 99.5 Cash, cash equivalents and restricted cash at beginning of period — — 17.8 133.8 — 151.6 Cash, cash equivalents and restricted cash at end of period $ — $ — $ 105.7 $ 145.4 $ — $ 251.1 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by (used for) operating activities $ 538.2 $ (203.8 ) $ 442.1 $ 1,533.7 $ — $ 2,310.2 Investing activities: Capital expenditures — — — (1,369.1 ) — (1,369.1 ) Cash paid for purchase of businesses, net of cash acquired — — — (3,374.2 ) — (3,374.2 ) Investment in unconsolidated entities — — — (11.2 ) — (11.2 ) Proceeds from sale of property, plant and equipment — — — 119.1 — 119.1 Proceeds from property, plant and equipment insurance settlement — — — 25.5 — 25.5 Intercompany notes issued — — (0.1 ) (75.7 ) 75.8 — Intercompany notes proceeds — 9.3 6.7 3,870.1 (3,886.1 ) — Intercompany capital investment (563.0 ) (563.0 ) — — 1,126.0 — Other — — 30.2 0.1 — 30.3 Net cash (used for) provided by investing activities (563.0 ) (553.7 ) 36.8 (815.4 ) (2,684.3 ) (4,579.6 ) Financing activities: Proceeds from issuance of notes — 2,498.2 — — — 2,498.2 Additions to revolving credit facilities — 67.2 — 155.0 — 222.2 Repayments to revolving credit facilities — (67.2 ) — (160.0 ) — (227.2 ) Additions to debt — 4,101.8 — 959.8 — 5,061.6 Repayments of debt — (2,400.0 ) (957.5 ) (2,274.1 ) — (5,631.6 ) Changes in commercial paper, net — 339.2 — — — 339.2 Other financing additions — 46.0 — 6.2 — 52.2 Issuances of common stock, net of related minimum tax withholdings 18.3 — — — — 18.3 Purchases of common stock (88.6 ) — — — — (88.6 ) Cash dividends paid to stockholders (467.9 ) — — — — (467.9 ) Cash distributions paid to noncontrolling interests — — — (4.3 ) — (4.3 ) Intercompany notes borrowing — — 75.7 0.1 (75.8 ) — Intercompany notes payments — (3,800.0 ) (70.1 ) (16.0 ) 3,886.1 — Intercompany capital receipt 563.0 — — 563.0 (1,126.0 ) — Other — (27.9 ) — 36.0 — 8.1 Net cash provided by (used for) financing activities 24.8 757.3 (951.9 ) (734.3 ) 2,684.3 1,780.2 Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — 4.0 — 4.0 Decrease in cash, cash equivalents and restricted cash — (0.2 ) (473.0 ) (12.0 ) — (485.2 ) Cash, cash equivalents and restricted cash at beginning of period — 0.2 490.8 145.8 — 636.8 Cash, cash equivalents and restricted cash at end of period $ — $ — $ 17.8 $ 133.8 $ — $ 151.6 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Net cash provided by operating activities $ 4.1 $ 563.4 $ 375.8 $ 1,016.3 $ (28.4 ) $ 1,931.2 Investing activities: Capital expenditures — — (1.2 ) (998.7 ) — (999.9 ) Cash paid for purchase of businesses, net of cash acquired — — — (239.9 ) — (239.9 ) Cash receipts on sold trade receivables — — — 461.6 — 461.6 Investment in unconsolidated entities — — — (114.3 ) — (114.3 ) Proceeds from sale of property, plant and equipment — — — 23.3 — 23.3 Proceeds from property, plant and equipment insurance settlement — — — 7.9 — 7.9 Intercompany notes issued — — (1.4 ) — 1.4 — Intercompany notes proceeds — — 4.5 — (4.5 ) — Intercompany capital investment — (2.0 ) — — 2.0 — Intercompany return of capital — — 82.6 — (82.6 ) — Other — — 18.6 27.6 — 46.2 Net cash (used for) provided by investing activities — (2.0 ) 103.1 (832.5 ) (83.7 ) (815.1 ) Financing activities: Proceeds from issuance of notes — 1,197.3 — — — 1,197.3 Additions to revolving credit facilities — — — 702.4 — 702.4 Repayments to revolving credit facilities — — — (572.2 ) — (572.2 ) Additions to debt — 2.7 — 852.5 — 855.2 Repayments of debt (0.1 ) (1,025.2 ) (22.5 ) (985.1 ) — (2,032.9 ) Other financing repayments — (106.7 ) (8.9 ) (154.3 ) — (269.9 ) Issuances of common stock, net of related minimum tax withholdings — 26.6 — — — 26.6 Purchases of common stock — (195.1 ) — — — (195.1 ) Cash dividends paid to stockholders — (440.9 ) — — — (440.9 ) Cash distributions paid to noncontrolling interests — — — (33.3 ) — (33.3 ) Intercompany notes borrowing — — — 1.4 (1.4 ) — Intercompany notes payments — — — (4.5 ) 4.5 — Intercompany capital receipt — — — 2.0 (2.0 ) — Intercompany capital distribution — — — (82.6 ) 82.6 — Intercompany dividends — — — (28.4 ) 28.4 — Other (4.0 ) (19.9 ) — 31.6 — 7.7 Net cash used for financing activities (4.1 ) (561.2 ) (31.4 ) (270.5 ) 112.1 (755.1 ) Effect of exchange rate changes on cash, cash equivalents and restricted cash — — — (28.2 ) — (28.2 ) Increase (decrease) in cash, cash equivalents and restricted cash — 0.2 447.5 (114.9 ) — 332.8 Cash, cash equivalents and restricted cash at beginning of period — — 43.3 260.7 — 304.0 Cash, cash equivalents and restricted cash at end of period $ — $ 0.2 $ 490.8 $ 145.8 $ — $ 636.8
Summary of Non-Cash Transactions	The table below summarizes these non-cash transactions. Year Ended September 30, 2020 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Investing activities: Intercompany notes issued $ — $ (13.9 ) $ (70.4 ) $ (117.0 ) $ 201.3 $ — Intercompany notes proceeds $ — $ — $ 80.6 $ 322.5 $ (403.1 ) $ — Intercompany capital investment $ (407.3 ) $ (625.6 ) $ (990.2 ) $ — $ 2,023.1 $ — Intercompany return of capital $ 442.0 $ 35.6 $ 727.0 $ — $ (1,204.6 ) $ — Financing activities: Intercompany notes borrowing $ — $ 117.0 $ — $ 84.3 $ (201.3 ) $ — Intercompany notes payments $ — $ — $ (322.5 ) $ (80.6 ) $ 403.1 $ — Intercompany capital receipt $ — $ — $ 625.2 $ 1,397.9 $ (2,023.1 ) $ — Intercompany capital distribution $ — $ (442.0 ) $ (21.2 ) $ (741.4 ) $ 1,204.6 $ — Intercompany dividends paid $ — $ — $ (48.3 ) $ (1,287.3 ) $ 1,335.6 $ — Year Ended September 30, 2019 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Operating activities: Intercompany receivables $ (140.9 ) $ — $ — $ — $ 140.9 $ — Intercompany payables $ — $ — $ — $ 140.9 $ (140.9 ) $ — Investing activities: Intercompany notes issued $ — $ (3,800.0 ) $ (4,667.2 ) $ (10,777.8 ) $ 19,245.0 $ — Intercompany notes proceeds $ — $ 4,519.8 $ 4,536.8 $ 6,822.0 $ (15,878.6 ) $ — Intercompany capital investment $ (10,396.2 ) $ (5,895.5 ) $ (6,889.3 ) $ — $ 23,181.0 $ — Intercompany return of capital $ 606.7 $ 1,479.6 $ 1,032.7 $ — $ (3,119.0 ) $ — Financing activities: Intercompany notes borrowing $ — $ 4,436.3 $ 2,541.5 $ 12,267.2 $ (19,245.0 ) $ — Intercompany notes payments $ — $ — $ (3,022.0 ) $ (12,856.6 ) $ 15,878.6 $ — Intercompany capital receipt $ — $ 10,396.2 $ 5,413.7 $ 7,371.1 $ (23,181.0 ) $ — Intercompany capital distribution $ (563.0 ) $ (606.7 ) $ (457.5 ) $ (1,491.8 ) $ 3,119.0 $ — Intercompany dividends paid $ — $ — $ (302.2 ) $ (1,435.0 ) $ 1,737.2 $ — Year Ended September 30, 2018 (In millions) Parent Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Total Investing activities: Intercompany notes issued $ — $ — $ — $ (392.1 ) $ 392.1 $ — Intercompany notes proceeds $ — $ — $ — $ 83.0 $ (83.0 ) $ — Intercompany capital investment $ — $ (755.3 ) $ (335.3 ) $ — $ 1,090.6 $ — Intercompany return of capital $ — $ 1,356.3 $ 766.0 $ — $ (2,122.3 ) $ — Financing activities: Intercompany notes borrowing $ — $ — $ 392.1 $ — $ (392.1 ) $ — Intercompany notes payments $ — $ (69.0 ) $ (14.0 ) $ — $ 83.0 $ — Intercompany capital receipt $ — $ — $ 736.9 $ 353.7 $ (1,090.6 ) $ — Intercompany capital distribution $ — $ — $ (1,356.3 ) $ (766.0 ) $ 2,122.3 $ — Intercompany dividends paid $ — $ — $ — $ (285.9 ) $ 285.9 $ —

Leases (Tables)

Leases (Tables)	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Schedule of Components of Lease Costs	Components of Lease Costs The following table presents certain information related to the lease costs for finance and operating leases (in millions): Year Ended September 30, 2020 Operating lease costs $ 201.2 Variable and short-term lease costs 105.5 Sublease income (6.7 ) Finance lease cost: Amortization of lease assets 10.5 Interest on lease liabilities 7.9 Total lease cost, net $ 318.4
Summary of Supplemental Balance Sheet Information Related to Leases	Supplemental Balance Sheet Information Related to Leases The table below presents the lease-related assets and liabilities recorded on the balance sheet (in millions): Consolidated Balance Sheet Caption September 30, 2020 Operating leases: Operating lease right-of-use asset Other assets $ 658.6 Current operating lease liabilities Other current liabilities $ 172.7 Noncurrent operating lease liabilities Other long-term liabilities 545.8 Total operating lease liabilities $ 718.5 Finance leases: Property, plant and equipment $ 143.2 Accumulated depreciation (19.1 ) Property, plant and equipment, net $ 124.1 Current finance lease liabilities Current portion of debt $ 9.0 Noncurrent finance lease liabilities Long-term debt due after one year 265.8 Total finance lease liabilities $ 274.8
Summary of Lease Term and Discount Rate	Lease Term and Discount Rate September 30, 2020 Weighted average remaining lease term: Operating leases 5.9 years Finance leases 9.0 years Weighted average discount rate: Operating leases 2.6 % Finance leases 4.0 %
Summary of Supplemental Cash Flow Information Related to Leases	Supplemental Cash Flow Information Related to Leases The table below presents supplemental cash flow information related to leases (in millions): Year Ended September 30, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows related to operating leases $ 204.1 Operating cash flows related to finance leases $ 7.8 Financing cash flows related to finance leases $ 10.1 ROU assets obtained in exchange for lease liabilities: Operating leases $ 124.4
Summary of Maturity of Lease Liabilities	Maturity of Lease Liabilities The table below reconciles the undiscounted cash flows for each of the first five years and total of the remaining years to the operating lease liabilities and finance lease liabilities recorded on the balance sheet (in millions): September 30, 2020 Operating Leases Finance Leases Total Fiscal 2021 $ 188.7 $ 16.3 $ 205.0 Fiscal 2022 151.4 15.3 166.7 Fiscal 2023 119.1 13.2 132.3 Fiscal 2024 94.1 12.0 106.1 Fiscal 2025 63.2 12.0 75.2 Thereafter 164.4 288.3 452.7 Total lease payments 780.9 357.1 1,138.0 Less: Interest (1) (62.4 ) (82.3 ) (144.7 ) Present value of future lease payments $ 718.5 $ 274.8 $ 993.3 (1)
Summary of Future Minimum Lease Payments Under All Noncancelable Operating Leases	As of September 30, 2019, future minimum lease payments under all noncancelable operating leases for the succeeding five fiscal years and thereafter are as follows (in millions): Fiscal 2020 $ 214.3 Fiscal 2021 180.1 Fiscal 2022 136.3 Fiscal 2023 108.3 Fiscal 2024 85.3 Thereafter 206.1 Total future minimum lease payments $ 930.4

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss and Other Comprehensive Loss (Tables)	12 Months Ended
	Sep. 30, 2020
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, 2020 and 2019 (in millions): Deferred (Loss) Income on Cash Flow Hedges Defined Benefit Pension and Postretirement Plans Foreign Currency Items Total (1) Balance at September 30, 2018 $ (0.2 ) $ (465.9 ) $ (229.2 ) $ (695.3 ) Other comprehensive income (loss) before reclassifications 1.1 (250.7 ) (142.7 ) (392.3 ) Amounts reclassified from accumulated other comprehensive (income) loss (0.2 ) 18.6 — 18.4 Net current period other comprehensive income (loss) 0.9 (232.1 ) (142.7 ) (373.9 ) Balance at September 30, 2019 $ 0.7 $ (698.0 ) $ (371.9 ) $ (1,069.2 ) Other comprehensive (loss) income before reclassifications (9.9 ) 5.1 (214.7 ) (219.5 ) Amounts reclassified from accumulated other comprehensive loss 3.6 38.6 — 42.2 Net current period other comprehensive (loss) income (6.3 ) 43.7 (214.7 ) (177.3 ) Reclassification of stranded tax effects — (73.4 ) — (73.4 ) Balance at September 30, 2020 $ (5.6 ) $ (727.7 ) $ (586.6 ) $ (1,319.9 ) (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, 2020 and 2019 (in millions): Years Ended September 30, 2020 2019 Pre-Tax Tax Net of Tax Pre-Tax Tax Net of Tax Amortization of defined benefit pension and postretirement items: (1) Actuarial losses (2) $ (47.7 ) 12.8 $ (34.9 ) $ (22.7 ) 5.9 $ (16.8 ) Prior service costs (2) (5.0 ) 1.3 (3.7 ) (2.4 ) 0.6 (1.8 ) Reclassification of stranded tax effects (3) — 73.4 73.4 — — — Subtotal defined benefit plans (52.7 ) 87.5 34.8 (25.1 ) 6.5 (18.6 ) Derivative Instruments: (1) Interest rate swap hedge (loss) gain (4) (2.3 ) 0.6 (1.7 ) 0.3 (0.1 ) 0.2 Natural gas commodity hedge loss (5) (2.6 ) 0.7 (1.9 ) — — — Subtotal derivative instruments (4.9 ) 1.3 (3.6 ) 0.3 (0.1 ) 0.2 Total reclassifications for the period $ (57.6 ) $ 88.8 $ 31.2 $ (24.8 ) $ 6.4 $ (18.4 ) (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 5. Retirement Plans (3) Amount reclassified to retained earnings as a result of the adoption of ASU 2018-02. (4) These accumulated other comprehensive income components are included in Interest expense, net. (5) These accumulated other comprehensive income components are included in Cost of goods sold.
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, 2020, 2019 and 2018, is as follows (in millions): Fiscal 2020 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (215.0 ) $ — $ (215.0 ) Deferred loss on cash flow hedges (13.3 ) 3.3 (10.0 ) Reclassification adjustment of net loss on cash flow hedges included in earnings 4.9 (1.3 ) 3.6 Net actuarial gain arising during period 34.6 (10.4 ) 24.2 Amortization and settlement recognition of net actuarial loss 48.3 (12.9 ) 35.4 Prior service cost arising during the period (26.9 ) 7.3 (19.6 ) Amortization of prior service cost 5.1 (1.3 ) 3.8 Consolidated other comprehensive loss (162.3 ) (15.3 ) (177.6 ) Less: Other comprehensive loss attributable to noncontrolling interests 0.3 — 0.3 Other comprehensive loss attributable to common stockholders $ (162.0 ) $ (15.3 ) $ (177.3 ) Fiscal 2019 Pre-Tax Tax Net of Tax Foreign currency translation loss $ (143.4 ) $ — $ (143.4 ) Deferred gain on cash flow hedges 1.5 (0.4 ) 1.1 Reclassification adjustment of net gain on cash flow hedges included in earnings (0.3 ) 0.1 (0.2 ) Net actuarial loss arising during period (335.9 ) 87.4 (248.5 ) Amortization and settlement recognition of net actuarial loss 23.3 (6.1 ) 17.2 Prior service cost arising during the period (3.9 ) 0.6 (3.3 ) Amortization of prior service cost 2.4 (0.6 ) 1.8 Consolidated other comprehensive loss (456.3 ) 81.0 (375.3 ) Less: Other comprehensive loss attributable to noncontrolling interests 1.5 (0.1 ) 1.4 Other comprehensive loss attributable to common stockholders $ (454.8 ) $ 80.9 $ (373.9 ) 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 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2020
Stock Based Compensation [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	As part of the KapStone Acquisition, we issued 2,665,462 options that were valued at a weighted average fair value of $20.99 per share using the Black-Scholes option pricing model. The weighted average significant assumptions used were: 2019 Expected term in years 3.1 Expected volatility 27.7 % Risk-free interest rate 3.0 % Dividend yield 4.1 %
Summary of Changes in Stock Options	The table below summarizes the changes in all stock options during the fiscal year ended September 30, 2020: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2019 4,396,177 $ 33.32 Exercised (840,433 ) 24.84 Expired (93,691 ) 38.21 Forfeited (5,756 ) 26.59 Outstanding at September 30, 2020 3,456,297 $ 35.26 3.0 $ 12.9 Exercisable at September 30, 2020 3,455,580 $ 35.27 3.0 $ 12.9 Vested and expected to vest at September 30, 2020 3,456,297 $ 35.26 3.0 $ 12.9
Summary of Changes in SARs	The table below summarizes the changes in all SARs during the fiscal year ended September 30, 2020: SARs Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding at September 30, 2019 34,972 $ 28.41 Exercised (15,343 ) 27.00 Expired (2,647 ) 23.65 Outstanding at September 30, 2020 16,982 $ 30.42 1.1 $ 0.1 Exercisable at September 30, 2020 16,982 $ 30.42 1.1 $ 0.1
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, 2020: Shares/Units Weighted Average Grant Date Fair Value Unvested at September 30, 2019 (1) 3,645,538 $ 51.94 Granted 4,446,175 31.53 Vested (766,431 ) 51.39 Forfeited (709,915 ) 51.27 Unvested at September 30, 2020 (1) 6,615,367 $ 38.36 (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 aggregate outstanding grants to be attained at levels less than target. However, it is possible that the performance attained may vary. The following table represents a summary of restricted stock shares granted in fiscal 2020, 2019 and 2018 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. 2020 2019 2018 Shares of restricted stock granted to non-employee directors (1) 49,236 39,792 23,285 Shares of restricted stock granted to employees: Shares granted for attainment of a performance condition at an amount in excess of target (2) — 1,149,592 45,964 Shares granted with a service condition and a Cash Flow Per Share performance condition at target (3) 869,065 652,465 432,655 Shares granted with a service condition and a relative Total Shareholder Return market condition at target (3) 152,595 407,300 259,695 Shares granted with a service condition (4) 889,030 682,264 354,512 Shares of restricted stock granted for annual bonus 2,486,249 — — Share of restricted stock assumed in purchase accounting: Shares granted with a service condition (5) — 742,032 — Total restricted stock granted 4,446,175 3,673,445 1,116,111 (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) These shares vest over approximately three to four years. (5) These shares vest over approximately one to three years. The following table represents a summary of restricted stock vested in fiscal 2020, 2019 and 2018 (in millions, except shares): 2020 2019 2018 Shares of restricted stock vested 766,431 2,933,556 697,717 Aggregate fair value of restricted stock vested $ 29.6 $ 115.2 $ 46.1

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted earnings per share under the two-class method (in millions, except per share data): September 30, 2020 2019 2018 Numerator: Net (loss) income attributable to common stockholders $ (690.9 ) $ 862.9 $ 1,906.1 Less: Distributed and undistributed income available to participating securities (0.1 ) (0.1 ) (0.2 ) Distributed and undistributed (loss) income available to common stockholders $ (691.0 ) $ 862.8 $ 1,905.9 Denominator: Basic weighted average shares outstanding 259.2 256.6 255.5 Effect of dilutive stock options and non-participating securities — 2.5 4.3 Diluted weighted average shares outstanding 259.2 259.1 259.8 Basic (loss) earnings per share attributable to common stockholders $ (2.67 ) $ 3.36 $ 7.46 Diluted (loss) earnings per share attributable to common stockholders $ (2.67 ) $ 3.33 $ 7.34

Financial Results by Quarter _2

Financial Results by Quarter (Unaudited) (Tables)	12 Months Ended
	Sep. 30, 2020
Financial Results By Quarter Unaudited [Abstract]
Schedule of Quarterly Financial Information	Fiscal 2020 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 4,423.7 $ 4,447.3 $ 4,236.3 $ 4,471.5 Gross profit $ 809.0 $ 804.8 $ 770.0 $ 813.4 (Gain) loss on disposal of assets $ (1.3 ) $ (5.6 ) $ 1.0 $ (10.4 ) Multiemployer pension withdrawal expense (income) $ — $ 0.9 $ (2.0 ) $ — Restructuring and other costs $ 30.1 $ 16.4 $ 9.7 $ 56.5 Goodwill impairment $ — $ — $ — $ 1,333.2 Loss on extinguishment of debt $ — $ (0.5 ) $ (0.6 ) $ (0.4 ) Income tax expense $ (46.5 ) $ (57.8 ) $ (19.2 ) $ (40.0 ) Consolidated net income (loss) $ 139.5 $ 148.9 $ 180.0 $ (1,154.5 ) Net income (loss) attributable to common stockholders $ 138.5 $ 148.1 $ 178.5 $ (1,156.0 ) Basic earnings (loss) per share attributable to common stockholders $ 0.54 $ 0.57 $ 0.69 $ (4.45 ) Diluted earnings (loss) per share attributable to common stockholders $ 0.53 $ 0.57 $ 0.69 $ (4.45 ) Fiscal 2019 First Quarter Second Quarter Third Quarter Fourth Quarter (In millions, except per share data) Net sales $ 4,327.4 $ 4,620.0 $ 4,690.0 $ 4,651.6 Gross profit $ 781.8 $ 899.6 $ 988.9 $ 1,078.7 (Gain) loss on disposal of assets $ (43.8 ) $ — $ 6.5 $ (3.9 ) Multiemployer pension withdrawal income $ — $ — $ (1.7 ) $ (4.6 ) Land and Development impairments $ — $ 13.0 $ — $ — Restructuring and other costs $ 54.4 $ 34.8 $ 17.9 $ 66.6 (Loss) gain on extinguishment of debt $ (1.9 ) $ 0.4 $ (3.2 ) $ (0.4 ) Income tax expense $ (62.7 ) $ (47.2 ) $ (77.6 ) $ (89.3 ) Consolidated net income $ 139.8 $ 161.9 $ 253.8 $ 312.4 Net income attributable to common stockholders $ 139.1 $ 160.4 $ 252.6 $ 310.8 Basic earnings per share attributable to common stockholders $ 0.55 $ 0.63 $ 0.98 $ 1.21 Diluted earnings per share attributable to common stockholders $ 0.54 $ 0.62 $ 0.98 $ 1.20

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details)	Oct. 01, 2019USD ($)	Dec. 22, 2017	Oct. 31, 2020MachineT	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)MMBTU	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Description of Business and Summary of Significant Accounting Policies [Line Items]
Bad debt expense					$ 19,900,000	$ 10,000,000	$ 4,200,000
Percentage of FIFO Inventory				41.00%	41.00%	39.00%
Interest Costs, Capitalized During Period					$ 24,600,000	$ 23,800,000	8,200,000
Percentage of our mill assets as measured at cost with a life of 25 years or less					90.00%
Increase in discount rate to estimate fair value of reporting unit					1.00%
Goodwill				$ 5,962,200,000	$ 5,962,200,000	$ 7,285,600,000	5,577,600,000	$ 5,528,300,000
Goodwill impairment loss				1,333,200,000	1,333,200,000
Goodwill impairment, after tax					$ 1,314,300,000
Finite-Lived Intangible Assets, Useful Life					15 years 6 months
Notional amount of natural gas commodity derivatives | MMBTU						8.4
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				72,300,000	$ 72,300,000	$ 72,500,000
Deferred maintenance costs				118,200,000	118,200,000	124,300,000
Foreign Currency Transaction Gain, after Tax					6,600,000	18,500,000	12,200,000
ASU 2018-02 [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Reclassification of stranded tax effects from accumulated other comprehensive income to retained earnings	$ 73,400,000
Subsequent Event [Member] | SBS End Markets [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Number of paper machines shut-down | Machine			1
Capacity removed due to shut-down of paper machines | T			200,000
Consumer Packaging [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Goodwill				$ 2,288,700,000	2,288,700,000	3,590,600,000	$ 3,610,900,000	$ 3,586,800,000
Goodwill impairment loss					1,333,200,000
North American Corrugated [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Reporting unit, percentage of fair value in excess of carrying value				10.00%
Goodwill				$ 3,533,000,000	3,533,000,000
Victory Packaging [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Reporting unit, percentage of fair value in excess of carrying value				10.00%
Goodwill				$ 41,100,000	41,100,000
Brazil Corrugated [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Reporting unit, percentage of fair value in excess of carrying value				10.00%
Goodwill				$ 99,400,000	$ 99,400,000
Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Approximate Range Receivables Due, Days					30 days
Reporting unit, discount rate				8.00%
Reporting unit, growth rate				0.50%
Finite-Lived Intangible Assets, Useful Life					1 year
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
Reporting unit, discount rate				14.00%
Reporting unit, growth rate				1.00%
Finite-Lived Intangible Assets, Useful Life					40 years
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				$ 250,200,000	$ 250,200,000	351,000,000
Interest Rate Contract [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Derivative, Notional Amount				600,000,000	600,000,000	$ 600,000,000
Natural Gas Commodity Derivatives [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Derivative, Notional Amount				$ 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, 2020	Sep. 30, 2019	Sep. 30, 2018
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of fiscal year	$ 53.2	$ 49.7	$ 45.8
Reduction in sales and charges to costs and expenses	270.8	259.6	202.8
Deductions	(257.7)	(256.1)	(198.9)
Balance at end of fiscal year	$ 66.3	$ 53.2	$ 49.7

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, 2020
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

Revenue Recognition - Schedule

Revenue Recognition - Schedule of Disaggregates Revenue by Geographical Market and Product Type (Segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Net sales	$ 4,471.5	$ 4,236.3	$ 4,447.3	$ 4,423.7	$ 4,651.6	$ 4,690	$ 4,620	$ 4,327.4	$ 17,578.8	$ 18,289	$ 16,285.1
Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									11,419.2	11,816.7
Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									6,333	6,606
Land and Development [Member]
Disaggregation Of Revenue [Line Items]
Net sales									18.9	23.4
Intersegment Sales [Member]
Disaggregation Of Revenue [Line Items]
Net sales									(192.3)	(157.1)	(167.8)
Intersegment Sales [Member] | Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									(71)	(75.3)	(87.3)
Intersegment Sales [Member] | Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									(121.3)	(81.8)	$ (80.5)
North America [Member]
Disaggregation Of Revenue [Line Items]
Net sales									15,781.5	16,349.2
North America [Member] | Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									10,975.8	11,314.7
North America [Member] | Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									4,978.2	5,166.6
North America [Member] | Land and Development [Member]
Disaggregation Of Revenue [Line Items]
Net sales									18.9	23.4
North America [Member] | Intersegment Sales [Member]
Disaggregation Of Revenue [Line Items]
Net sales									(191.4)	(155.5)
South America [Member]
Disaggregation Of Revenue [Line Items]
Net sales									463.2	510.4
South America [Member] | Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									393.1	437.2
South America [Member] | Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									70.1	73.2
Europe [Member]
Disaggregation Of Revenue [Line Items]
Net sales									1,014	1,066.2
Europe [Member] | Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									7.9	1.6
Europe [Member] | Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									1,006.4	1,064.7
Europe [Member] | Intersegment Sales [Member]
Disaggregation Of Revenue [Line Items]
Net sales									(0.3)	(0.1)
Asia Pacific [Member]
Disaggregation Of Revenue [Line Items]
Net sales									320.1	363.2
Asia Pacific [Member] | Corrugated Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									42.4	63.2
Asia Pacific [Member] | Consumer Packaging [Member]
Disaggregation Of Revenue [Line Items]
Net sales									278.3	301.5
Asia Pacific [Member] | Intersegment Sales [Member]
Disaggregation Of Revenue [Line Items]
Net sales									$ (0.6)	$ (1.5)

Revenue Recognition - Summary o

Revenue Recognition - Summary of Opening and Closing Balances of Contract Assets and Contract Liabilities (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Disaggregation Of Revenue [Abstract]
Short-Term Contract Assets, Beginning balance	$ 188
(Decrease) / Increase in Short-Term Contract Assets	(2.2)
Short-Term Contract Assets, Ending balance	185.8
Short-Term Contract Liabilities, Beginning balance	7.7
(Decrease) / increase in Short-Term Contract Liabilities	4.3
Short-Term Contract Liabilities, Ending balance	$ 12

Acquisitions and Investments -

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

Nov. 02, 2018USD ($)$ / sharesshares

Sep. 04, 2018USD ($)

Jan. 05, 2018USD ($)T

Oct. 20, 2017USD ($)

Apr. 01, 2016USD ($)PackagingFacility

Apr. 01, 2021

Sep. 30, 2020USD ($)$ / shares

Apr. 01, 2020

Sep. 30, 2019USD ($)$ / shares

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)

Apr. 30, 2017

Business Acquisition [Line Items]

Common Stock, Par or Stated Value Per Share | $ / shares

$ 0.01

$ 0.01

$ 0.01

Number of WRKCo Shares to WestRock Shares | shares

1

Finite-Lived Intangible Assets, Useful Life

15 years 6 months

Goodwill

$ 5,962.2

$ 7,285.6

$ 5,577.6

$ 5,528.3

Equity Method Investments

$ 429.6

$ 469.1

$ 457.8

Customer Relationships [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

15 years 6 months

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

KapStone Acquisition [Member]

Business Acquisition [Line Items]

Acquisition date

Nov. 2, 2018

Common Stock, Par or Stated Value Per Share | $ / shares

$ 0.0001

Business Acquisition, Share Price | $ / shares

$ 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

$ 4,900

Consideration paid in cash

$ 3,300

Business acquisition, number of shares issued | shares

1,600,000

Business Combination, Consideration Transferred, Equity Interests Issued and Issuable

$ 70.1

Business acquisition, percentage of equity interest on shares issued and outstanding

0.60%

Fair value of share-based awards issued in business combinations

$ 70.8

Goodwill

1,755

Property, plant and equipment, net

1,910.3

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

2,442.1

Cash and cash equivalents

8.6

Other long-term assets

$ 27.9

KapStone Acquisition [Member] | Minimum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

1 year

KapStone Acquisition [Member] | Maximum [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

20 years

WRKCo Inc. [Member]

Business Acquisition [Line Items]

Common Stock, Par or Stated Value Per Share | $ / shares

$ 0.01

Schluter Acquisition [Member]

Business Acquisition [Line Items]

Acquisition date

Sep. 4, 2018

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

$ 50.6

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

7.5

Goodwill

23.7

Property, plant and equipment, net

26.5

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

$ 21.1

Schluter Acquisition [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Finite-Lived Intangible Assets, Useful Life

10 years 6 months

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

$ 9.1

Plymouth Packaging [Member]

Business Acquisition [Line Items]

Acquisition date

Jan. 5, 2018

Goodwill

$ 59.6

Property, plant and equipment, net

36.2

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

12.6

Business Acquisition, Cost of Acquired Entity, Preliminary Purchase Price

203.9

Cash and cash equivalents

$ 3.1

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]

Finite-Lived Intangible Assets, Useful Life

13 years

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

$ 61.9

Grupo Gondi Investment [Member]

Business Acquisition [Line Items]

Acquisition date

Apr. 1, 2016

Payments to Acquire Interest in Joint Venture

$ 108

$ 175

Number of corrugated packaging facilities | PackagingFacility

3

Equity Method Investment, Ownership Percentage

32.30%

25.00%

27.00%

Equity Method Investments

$ 300

Equity Method Investment, Ownership Percentage to Sell

24.00%

Grupo Gondi Investment [Member] | Forecast [Member]

Business Acquisition [Line Items]

Option to purchase additional equity interest from partners percentage

18.70%

Equity Method Investment, Additional Information

If we exercise our right to purchase the additional 18.7% equity interest, the Partners may elect to sell us the Partners’ remaining interest at fair market value at that time, or a portion thereof in the future in accordance with the terms of the option agreement

Acquisitions and Investments _2

Acquisitions and Investments - Summary of Fair Values of Assets Acquired and Liabilities Assumed by Major Class of Assets and Liabilities and Measurement Period Adjustments (Details) - USD ($) $ in Millions		Sep. 30, 2020	Sep. 30, 2019	Nov. 02, 2018	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Goodwill		$ 5,962.2	$ 7,285.6		$ 5,577.6	$ 5,528.3
KapStone Acquisition [Member]
Business Acquisition [Line Items]
Cash and cash equivalents				$ 8.6
Current assets, excluding cash and cash equivalents				878.9
Property, plant and equipment, net				1,910.3
Goodwill				1,755
Intangible assets				1,336.1
Other long-term assets				27.9
Total assets acquired				5,916.8
Current portion of debt				33.3
Current liabilities				337.5
Long-term debt due after one year				1,333.4
Accrued pension and other long-term benefits				9.8
Deferred income taxes				609.7
Other long-term liabilities				118.4
Total liabilities assumed				2,442.1
Net assets acquired				3,474.7
KapStone Acquisition [Member] | Measurement Period Adjustments [Member]
Business Acquisition [Line Items]
Current assets, excluding cash and cash equivalents	[1]			(30.2)
Property, plant and equipment, net	[1]			11.5
Goodwill	[1]			0.5
Intangible assets	[1]			30.3
Other long-term assets	[1]			(0.1)
Total assets acquired	[1]			12
Current liabilities	[1]			7.9
Accrued pension and other long-term benefits	[1]			2.8
Deferred income taxes	[1]			(1.4)
Other long-term liabilities	[1]			2.7
Total liabilities assumed	[1]			12
KapStone Acquisition [Member] | As Adjusted [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	[2]			8.6
Current assets, excluding cash and cash equivalents	[2]			848.7
Property, plant and equipment, net	[2]			1,921.8
Goodwill	[2]			1,755.5
Intangible assets	[2]			1,366.4
Other long-term assets	[2]			27.8
Total assets acquired	[2]			5,928.8
Current portion of debt	[2]			33.3
Current liabilities	[2]			345.4
Long-term debt due after one year	[2]			1,333.4
Accrued pension and other long-term benefits	[2]			12.6
Deferred income taxes	[2]			608.3
Other long-term liabilities	[2]			121.1
Total liabilities assumed	[2]			2,454.1
Net assets acquired	[2]			$ 3,474.7
[1]
[2]	The measurement period adjustments were primarily due to refinements to third party appraisals and carrying amounts of certain assets and liabilities, as well as adjustments to certain tax accounts based on, among other things, adjustments to deferred tax liabilities. The net impact of the measurement period adjustments to goodwill were essentially flat.

Acquisitions and Investments _3

Acquisitions and Investments - Summary of Weighted Average Life and Fair Value of Intangible Asset Recognized in KapStone Acquisition, Excluding Goodwill (Details) - KapStone Acquisition [Member] $ in Millions	Nov. 02, 2018USD ($)
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	11 years 10 months 24 days
Amounts Recognized as of the Acquisition Date	$ 1,366.4
Customer Relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	11 years 8 months 12 days
Amounts Recognized as of the Acquisition Date	$ 1,303
Trademarks and Tradenames [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	16 years 10 months 24 days
Amounts Recognized as of the Acquisition Date	$ 54.2
Favorable Contracts [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	6 years
Amounts Recognized as of the Acquisition Date	$ 9.2

Restructuring and Other Costs -

Restructuring and Other Costs - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring And Related Activities [Abstract]
Restructuring and other costs	$ 112.7	$ 173.7	$ 105.4
Restructuring and other costs, noncash	$ 29.8	$ 56.5	$ 27

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, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring And Related Activities [Abstract]
Restructuring									$ 93.7	$ 111	$ 39.5
Other									19	62.7	65.9
Restructuring and Other Costs	$ 56.5	$ 9.7	$ 16.4	$ 30.1	$ 66.6	$ 17.9	$ 34.8	$ 54.4	$ 112.7	$ 173.7	$ 105.4

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, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	$ 93.7	$ 111	$ 39.5
Restructuring and Related Cost, Cost Incurred to Date	403
Restructuring and Related Cost, Expected Cost	405.9
Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	25.7	32.6	9.7
Restructuring and Related Cost, Cost Incurred to Date	151.2
Restructuring and Related Cost, Expected Cost	151.2
Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	49.6	60.5	9.9
Restructuring and Related Cost, Cost Incurred to Date	174.7
Restructuring and Related Cost, Expected Cost	174.7
Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	3.6	5.8	5.8
Restructuring and Related Cost, Cost Incurred to Date	17.7
Restructuring and Related Cost, Expected Cost	18.2
Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2.6	4.1	4.2
Restructuring and Related Cost, Cost Incurred to Date	23
Restructuring and Related Cost, Expected Cost	25.1
Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	12.2	8	9.9
Restructuring and Related Cost, Cost Incurred to Date	36.4
Restructuring and Related Cost, Expected Cost	36.7
Corporate, Non-Segment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	22.7	40	5.6
Restructuring and Related Cost, Cost Incurred to Date	68.4
Restructuring and Related Cost, Expected Cost	68.4
Corporate, Non-Segment [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	21.1	37.5	0.8
Restructuring and Related Cost, Cost Incurred to Date	59.4
Restructuring and Related Cost, Expected Cost	59.4
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	1.6	2.5	4.8
Restructuring and Related Cost, Cost Incurred to Date	9
Restructuring and Related Cost, Expected Cost	9
Corrugated Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	13.8	58.9	11.6
Restructuring and Related Cost, Cost Incurred to Date	174.3
Restructuring and Related Cost, Expected Cost	176.9
Corrugated Packaging [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2.2	32.1	2.9
Restructuring and Related Cost, Cost Incurred to Date	96.3
Restructuring and Related Cost, Expected Cost	96.3
Corrugated Packaging [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	8.7	16.9	1.9
Restructuring and Related Cost, Cost Incurred to Date	43.2
Restructuring and Related Cost, Expected Cost	43.2
Corrugated Packaging [Member] | Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2.2	4.8	3.4
Restructuring and Related Cost, Cost Incurred to Date	10.4
Restructuring and Related Cost, Expected Cost	10.9
Corrugated Packaging [Member] | Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2.6	3.9	3.3
Restructuring and Related Cost, Cost Incurred to Date	21.1
Restructuring and Related Cost, Expected Cost	23.2
Corrugated Packaging [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	(1.9)	1.2	0.1
Restructuring and Related Cost, Cost Incurred to Date	3.3
Restructuring and Related Cost, Expected Cost	3.3
Consumer Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	55.2	12	19
Restructuring and Related Cost, Cost Incurred to Date	139.7
Restructuring and Related Cost, Expected Cost	140
Consumer Packaging [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	23.5	0.5	6.8
Restructuring and Related Cost, Cost Incurred to Date	53.1
Restructuring and Related Cost, Expected Cost	53.1
Consumer Packaging [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	19.8	6	6.9
Restructuring and Related Cost, Cost Incurred to Date	58.3
Restructuring and Related Cost, Expected Cost	58.3
Consumer Packaging [Member] | Equipment and Inventory Relocation Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	1.4	1	2.4
Restructuring and Related Cost, Cost Incurred to Date	7.3
Restructuring and Related Cost, Expected Cost	7.3
Consumer Packaging [Member] | Facility Carrying Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		0.2	0.9
Restructuring and Related Cost, Cost Incurred to Date	1.9
Restructuring and Related Cost, Expected Cost	1.9
Consumer Packaging [Member] | Other Costs Related to Restructuring and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	10.5	4.3	2
Restructuring and Related Cost, Cost Incurred to Date	19.1
Restructuring and Related Cost, Expected Cost	19.4
Land and Development [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2	0.1	3.3
Restructuring and Related Cost, Cost Incurred to Date	20.6
Restructuring and Related Cost, Expected Cost	20.6
Land and Development [Member] | Net Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
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		$ 0.1	0.3
Restructuring and Related Cost, Cost Incurred to Date	13.8
Restructuring and Related Cost, Expected Cost	13.8
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	2		$ 3
Restructuring and Related Cost, Cost Incurred to Date	5
Restructuring and Related Cost, Expected Cost	$ 5

Restructuring and Other Costs_4

Restructuring and Other Costs - Schedule of Acquisition, Divestiture and Integration Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Acquisition costs	$ 0.2	$ 28.2	$ 38.2
Integration costs	18.7	34.3	22
Divestiture costs	0.1	0.2	0.3
Other total	19	62.7	65.9
Other Segments [Member]
Restructuring Cost And Reserve [Line Items]
Acquisition costs	0.2	28.2	38.2
Integration costs	18.7	34.3	27.4
Divestiture costs	0.1	0.2	0.3
Other total	$ 19	$ 62.7	$ 65.9

Restructuring and Other Costs_5

Restructuring and Other Costs - Schedule of Changes in Restructuring Accrual Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring And Other Costs [Abstract]
Accrual at beginning of fiscal year	$ 32.3	$ 31.6	$ 47.4
Additional accruals	51.3	60	16.5
Payments	(56.6)	(55.9)	(29.8)
Adjustment to accruals	(6.2)	(3.2)	(1)
Foreign currency rate changes and other	(3.6)	(0.2)	(1.5)
Accrual at end of fiscal year	$ 17.2	$ 32.3	$ 31.6

Restructuring and Other Costs_6

Restructuring and Other Costs - Schedule of Reconciliation of Accruals and Charges (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring And Other Costs [Abstract]
Additional accruals and adjustments to accruals (see table above)										$ 45.1	$ 56.8	$ 15.5
Acquisition costs										0.2	28.2	38.2
Integration costs										18.7	34.3	22
Divestiture costs										0.1	0.2	0.3
Net property, plant and equipment										25.7	32.6	9.7
Severance and other employee costs										1.6	6.8	1.3
Equipment and inventory relocation costs										3.6	5.8	5.8
Facility carrying costs										2.6	4.1	4.2
Other costs	[1]									15.1	4.9	8.4
Restructuring and Other Costs		$ 56.5	$ 9.7	$ 16.4	$ 30.1	$ 66.6	$ 17.9	$ 34.8	$ 54.4	$ 112.7	$ 173.7	$ 105.4
[1]	Other costs primarily includes lease and contract termination costs.

Retirement Plans - Schedule of

Retirement Plans - Schedule of Allocation of Plan Assets - (Details) - Pension Plan [Member]	Sep. 30, 2020	Sep. 30, 2019
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	19.00%	15.00%
Defined Benefit Plan, Actual Plan Asset Allocations	22.00%	13.00%
Equity Securities [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	20.00%	20.00%
Defined Benefit Plan, Actual Plan Asset Allocations	21.00%	22.00%
Fixed Income Investments [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	75.00%	75.00%
Defined Benefit Plan, Actual Plan Asset Allocations	72.00%	70.00%
Fixed Income Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	72.00%	72.00%
Defined Benefit Plan, Actual Plan Asset Allocations	72.00%	71.00%
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%	9.00%
Short-term Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	2.00%	1.00%
Defined Benefit Plan, Actual Plan Asset Allocations	2.00%	2.00%
Other Investments [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	5.00%	9.00%
Defined Benefit Plan, Actual Plan Asset Allocations	3.00%	8.00%
Other Investments [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets	6.00%	7.00%
Defined Benefit Plan, Actual Plan Asset Allocations	5.00%	5.00%

Retirement Plans - Additional I

Retirement Plans - Additional Information (Details) $ in Millions	1 Months Ended		12 Months Ended
	Oct. 31, 2019USD ($)Letter	Sep. 30, 2019USD ($)	Sep. 30, 2021	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Apr. 30, 2020USD ($)	Feb. 29, 2020USD ($)
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
Defined benefit plan, accumulated benefit obligation		$ 6,438.9		6,682.2	$ 6,438.9
Defined benefit plan, effect of one percentage point increase on accumulated postretirement benefit obligation				10
Defined benefit plan, effect of one percentage point increase on service and interest cost components				1
Defined benefit plan, effect of one percentage point decrease on accumulated postretirement benefit obligation				8
Defined benefit plan, effect of one percentage point decrease on service and interest cost components				1
Multiemployer Plans, Withdrawal Obligation		237.2		$ 252	237.2
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%
Percentage of Employees Covered by Collective Bargaining Agreements				56.00%
Percentage of Employees Working Under Expired Collective Bargaining Agreement				15.00%
Percentage of Employees Covered By Collective Bargaining Agreements Expiring in One Year				21.00%
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				$ 150.1	150.9	$ 113.7
Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation		$ 170.3			$ 170.3
Periods of Payments Used to Calculate Withdrawal Liability in Connection with PIUMPF Withdrawal		20 years
Withdrawal obligation, per month		$ 0.7
Withdrawal obligation accumulated funding deficiency								$ 51.2
Subsidiary [Member] | Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation	$ 2.3
Periods of Payments Used to Calculate Withdrawal Liability in Connection with PIUMPF Withdrawal	20 years
Number of additional demand letters | Letter	2
Withdrawal obligation accumulated funding deficiency	$ 2						$ 1.3
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 Pension Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation						$ 4.2
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Adjustment to Pri-2012 mortality tables with specific gender and job classification				5.00%	6.00%
Adjustment to Rp2014 tables with specific gender and job classification						10.00%
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Adjustment to Pri-2012 mortality tables with specific gender and job classification				12.00%	12.00%
Adjustment to Rp2014 tables with specific gender and job classification						14.00%
Defined Contribution Plan Employer Contribution on Basic Salary, Matching Contribution				5.00%
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				$ 23
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				6.25%	6.50%	6.50%
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				$ 222.3
Defined benefit plan, pension plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation				222.2
Defined benefit plan, plan with benefit obligation in excess of plan assets, fair value of plan assets				$ 36.8
Pension Plan [Member] | United States [Member] | Forecast [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			6.00%
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 Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets				4.26%	4.69%	4.98%
Pension Plan [Member] | Foreign Plan [Member] | Forecast [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			3.73%
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				$ 168.9
Pension and other postretirement plans, liabilities				$ 176.1

Retirement Plans - Schedule o_2

Retirement Plans - Schedule of Weighted-Average Assumptions Used to Measure Benefit Plan Obligations (Details)	Sep. 30, 2020	Sep. 30, 2019
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	3.01%	3.35%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	2.50%	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	2.16%	2.42%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	2.68%	2.65%
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	3.00%	3.34%
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	4.84%	5.64%

Retirement Plans - Schedule o_3

Retirement Plans - Schedule of Changes in Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Prepaid pension asset	$ 368.7	$ 224.7
Pension liabilities, net of current portion	(305.2)	(294)
Postretirement benefit liabilities, net of current portion	(145.4)	(162.1)
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	52.6	42.8	$ 44.8
Interest cost	198.6	232.6	204.6
Pension Plan [Member] | United States [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year	5,048.9	3,783.5
Service cost	44.2	36
Interest cost	165	189.2
Amendments	25.2	0.4
Actuarial (gain) loss	214.3	694.4
Plan participant contributions	0	0
Benefits paid	(233.1)	(216.8)
Business combinations	0	561.2
Curtailments	0	1
Settlements	0	0
Foreign currency rate changes	0	0
Benefit obligation at end of fiscal year	5,264.5	5,048.9	3,783.5
Fair value of plan assets at beginning of fiscal year	5,005.3	3,921.2
Actual gain on plan assets	582.6	731.7
Employer contributions	14.9	13
Plan participant contributions	0	0
Benefits paid	(233.1)	(216.8)
Business combinations	0	556.2
Settlements	0	0
Foreign currency rate changes	0	0
Fair value of plan assets at end of fiscal year	5,369.7	5,005.3	3,921.2
Funded status	105.2	(43.6)
Prepaid pension asset	290.6	143.3
Other current liabilities	(10.7)	(14.6)
Pension liabilities, net of current portion	(174.7)	(172.3)
Over (under) funded status at end of fiscal year	105.2	(43.6)
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year	1,443.1	1,340.2
Service cost	8.4	6.8
Interest cost	33.6	43.4
Amendments	(0.2)	3.1
Actuarial (gain) loss	41.9	181
Plan participant contributions	2	2.2
Benefits paid	(72)	(78.3)
Business combinations	0	0.7
Curtailments	3.2	0
Settlements	(9)	(1.7)
Foreign currency rate changes	20.5	(54.3)
Benefit obligation at end of fiscal year	1,471.5	1,443.1	1,340.2
Fair value of plan assets at beginning of fiscal year	1,400.9	1,350.2
Actual gain on plan assets	65.4	172.9
Employer contributions	7.6	12.1
Plan participant contributions	2	2.2
Benefits paid	(72)	(78.3)
Business combinations	0	0
Settlements	(9)	(1.7)
Foreign currency rate changes	23.1	(56.5)
Fair value of plan assets at end of fiscal year	1,418	1,400.9	1,350.2
Funded status	(53.5)	(42.2)
Prepaid pension asset	78.1	81.4
Other current liabilities	(1.1)	(1.9)
Pension liabilities, net of current portion	(130.5)	(121.7)
Over (under) funded status at end of fiscal year	(53.5)	(42.2)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	1.3	1.2	1.5
Interest cost	6.9	7.7	7.9
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year	98.3	91
Service cost	0.6	0.7
Interest cost	3.2	4.1
Amendments	(0.1)	0.4
Actuarial (gain) loss	(3.1)	1.6
Benefits paid	(5.3)	(6.6)
Business combinations	0	7.1
Foreign currency rate changes	0	0
Benefit obligation at end of fiscal year	93.6	98.3	91
Fair value of plan assets at beginning of fiscal year	0	0
Employer contributions	5.3	6.6
Benefits paid	(5.3)	(6.6)
Fair value of plan assets at end of fiscal year	0	0	0
Funded status	(93.6)	(98.3)
Other current liabilities	(8)	(8.9)
Postretirement benefit liabilities, net of current portion	(85.6)	(89.4)
Over (under) funded status at end of fiscal year	(93.6)	(98.3)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of fiscal year	75.7	55.5
Service cost	0.7	0.5
Interest cost	3.7	3.6
Amendments	2	0
Actuarial (gain) loss	(5.3)	22.2
Benefits paid	(2.9)	(2.9)
Business combinations	0	0
Foreign currency rate changes	(11.4)	(3.2)
Benefit obligation at end of fiscal year	62.5	75.7	55.5
Fair value of plan assets at beginning of fiscal year	0	0
Employer contributions	2.9	2.9
Benefits paid	(2.9)	(2.9)
Fair value of plan assets at end of fiscal year	0	0	$ 0
Funded status	(62.5)	(75.7)
Other current liabilities	(2.7)	(3)
Postretirement benefit liabilities, net of current portion	(59.8)	(72.7)
Over (under) funded status at end of fiscal year	$ (62.5)	$ (75.7)

Retirement Plans - Schedule o_4

Retirement Plans - Schedule of Amounts in Accumulated Other Comprehensive (Income) Loss (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 753.2	$ 854.7
Prior service cost (credit)	45.6	27.6
Total accumulated other comprehensive loss (income)	798.8	882.3
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	188.6	168.8
Prior service cost (credit)	2.4	3.4
Total accumulated other comprehensive loss (income)	191	172.2
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(10.6)	(8)
Prior service cost (credit)	(5.7)	(8.3)
Total accumulated other comprehensive loss (income)	(16.3)	(16.3)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	13	18.8
Prior service cost (credit)	1.2	(0.9)
Total accumulated other comprehensive loss (income)	$ 14.2	$ 17.9

Retirement Plans - Schedule o_5

Retirement Plans - Schedule of Amounts Recognized in Other Comprehensive Loss (Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during period	$ (34.6)	$ 335.9	$ 29
Amortization and settlement recognition of net actuarial (loss) gain	(48.3)	(23.3)	(20.9)
Prior service cost (credit) arising during period	26.9	3.9	7.8
Amortization of prior service (cost) credit	(5.1)	(2.4)	(0.3)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during period	(26.2)	312	38.7
Amortization and settlement recognition of net actuarial (loss) gain	(48.2)	(25.3)	(20.6)
Prior service cost (credit) arising during period	25	3.5	9.3
Amortization of prior service (cost) credit	(7.8)	(5.2)	(4.7)
Net other comprehensive (income) loss recognized	(57.2)	285	22.7
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during period	(8.4)	23.9	(9.7)
Amortization and settlement recognition of net actuarial (loss) gain	(0.1)	2	(0.3)
Prior service cost (credit) arising during period	1.9	0.4	(1.5)
Amortization of prior service (cost) credit	2.7	2.8	4.4
Net other comprehensive (income) loss recognized	$ (3.9)	$ 29.1	$ (7.1)

Retirement Plans - Summary of C

Retirement Plans - Summary of Components of Net Pension Income and Summary of Components of Postretirement Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 52.6	$ 42.8	$ 44.8
Interest cost	198.6	232.6	204.6
Expected return on plan assets	(362.3)	(340.2)	(328.4)
Amortization of net actuarial loss (gain)	46.8	24.5	21.2
Amortization of prior service cost (credit)	7.5	5.2	4.7
Curtailment loss (gain)	0.4	1	(0.6)
Settlement loss (gain)	1.4	(0.2)	(0.5)
Company defined benefit plan (income) cost	(55)	(34.3)	(54.2)
Multiemployer and other plans	2	1.4	1.4
Net pension (income) cost	(53)	(32.9)	(52.8)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.3	1.2	1.5
Interest cost	6.9	7.7	7.9
Amortization of net actuarial loss (gain)	0.1	(2)	0.3
Amortization of prior service cost (credit)	(2.7)	(2.8)	(4.4)
Curtailment loss (gain)	0	0	(0.1)
Net pension (income) cost	$ 5.6	$ 4.1	$ 5.2

Retirement Plans - Schedule o_6

Retirement Plans - Schedule of Weighted-Average Assumptions Used in Calculation of Benefit Plan Expense (Details)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.35%	4.50%	4.09%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Cost, Rate of Compensation Increase	3.00%	3.00%	3.00%
Expected long-term rate of return on plan assets	6.25%	6.50%	6.50%
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.42%	3.42%	3.26%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Cost, Rate of Compensation Increase	2.65%	2.67%	2.65%
Expected long-term rate of return on plan assets	4.26%	4.69%	4.98%
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	3.34%	4.50%	4.09%
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	5.64%	6.61%	6.51%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Cost, Rate of Compensation Increase			7.37%

Retirement Plans - Schedule o_7

Retirement Plans - Schedule of Estimated Losses Gains Amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost (Details) $ in Millions	Sep. 30, 2020USD ($)
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of (Gain) Loss, Next Fiscal Year	$ 20.9
Expected Amortization of Prior Service (Credit) Cost, Next Fiscal Year	7.8
Expected Amortization, Next Fiscal Year	28.7
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of (Gain) Loss, Next Fiscal Year	10.4
Expected Amortization of Prior Service (Credit) Cost, Next Fiscal Year	0.2
Expected Amortization, Next Fiscal Year	10.6
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of (Gain) Loss, Next Fiscal Year	(1.3)
Expected Amortization of Prior Service (Credit) Cost, Next Fiscal Year	(2.5)
Expected Amortization, Next Fiscal Year	(3.8)
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Amortization of (Gain) Loss, Next Fiscal Year	0.1
Expected Amortization of Prior Service (Credit) Cost, Next Fiscal Year	0.1
Expected Amortization, Next Fiscal Year	$ 0.2

Retirement Plans - Schedule o_8

Retirement Plans - Schedule of Estimated Benefit Payments (Details) $ in Millions	Sep. 30, 2020USD ($)
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2021	$ 264.6
Fiscal 2022	273.5
Fiscal 2023	277.6
Fiscal 2024	282
Fiscal 2025	278
Fiscal Years 2026 – 2030	1,422
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2021	71.9
Fiscal 2022	71.5
Fiscal 2023	71.7
Fiscal 2024	71
Fiscal 2025	71.3
Fiscal Years 2026 – 2030	350
Other Postretirement Benefits Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2021	8.6
Fiscal 2022	7.6
Fiscal 2023	7.2
Fiscal 2024	6.9
Fiscal 2025	6.6
Fiscal Years 2026 – 2030	29.2
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2021	2.7
Fiscal 2022	2.7
Fiscal 2023	2.8
Fiscal 2024	2.9
Fiscal 2025	3
Fiscal Years 2026 – 2030	$ 16.7

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, 2020	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at NAV		$ 2,123.2	$ 2,054.8
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		6,787.7	6,406.2
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value Investments		4,664.5	4,351.4
Assets measured at NAV	[1]	2,123.2	2,054.8
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		550.6	813
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		4,113.9	3,538.4
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]	253	184.2
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]	253	183.5
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]		0.7
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]	4	6.5
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]	4	6.5
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	[3]	103.1	125.6
Fair Value, Measurements, Recurring [Member] | Non-US government 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	[3]		0.2
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	[3]	103.1	125.4
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	[3]	2,875.3	2,156
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	[3]	124.9	137.6
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	[3]	2,750.4	2,018.4
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	[3]	540.7	432.9
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	[3]		5.7
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	[3]	540.7	427.2
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	[4]	388	379.3
Fair Value, Measurements, Recurring [Member] | Other Fixed Income 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	[4]		10.8
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	[4]	388	368.5
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	[5]	168.7	468.7
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	[5]	168.7	468.7
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	[6]	331.7	598.2
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	[6]	$ 331.7	$ 598.2
[1]	Investments that are measured at net asset value (“ NAV
[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]	The level 1 non-U.S. government securities investment is an exchange cleared swap 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]	U.S. government securities include treasury and agency debt. These investments are valued using broker quotes in an active market.

Retirement Plans - Summary of_2

Retirement Plans - Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis (Parenthetical) (Details) - $ / Unit	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Retirement Plans [Abstract]
Short-term investments per units	1	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, 2020	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Defined Benefit Plans, Fair Value of Plan Assets		$ 2,123.2	$ 2,054.8
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments		228.9	113.1
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]	$ 39.2	$ 42.9
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	30 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	[2]	$ 1,416.9	$ 1,188.6
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	[2]	$ 228.9	$ 113.1
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	[2]	60 days	60 days
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]	$ 667.1	$ 823.3
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.
[2]	Commingled fund investments are valued at the NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques.
[3]	Fixed income and fixed income related instruments consist of commingled debt funds, which are valued at their NAV per share multiplied by the number of shares held. The determination of NAV for the commingled funds includes market pricing of the underlying assets as well as broker quotes and other valuation techniques.

Retirement Plans - Schedule o_9

Retirement Plans - Schedule of Health Care Cost Trend Rates (Details) - Other Postretirement Benefits Plan [Member]	12 Months Ended
	Sep. 30, 2020
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	5.57%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.42%
Year the rate reaches the ultimate trend rate	2038
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	5.25%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	5.25%
Year the rate reaches the ultimate trend rate	2020

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
United States									$ (440.7)	$ 891.6	$ 736.7
Foreign									(81.9)	253.1	298.1
(Loss) income before income taxes									(522.6)	1,144.7	1,034.8
Deferred income taxes:
Total deferred expense (benefit)									43	37.1	(1,069.4)
Total income tax expense (benefit)	$ 40	$ 19.2	$ 57.8	$ 46.5	$ 89.3	$ 77.6	$ 47.2	$ 62.7	163.5	276.8	(874.5)
Continuing Operations [Member]
Current income taxes:
Federal									31.6	134.7	83
State									23.5	34.9	26.8
Foreign									66.8	69.5	86.6
Total current expense									121.9	239.1	196.4
Deferred income taxes:
Federal									42.4	44.1	(1,108.6)
State									6.2	6.1	53.2
Foreign									(7)	(12.5)	(15.5)
Total deferred expense (benefit)									41.6	37.7	(1,070.9)
Total income tax expense (benefit)									$ 163.5	$ 276.8	$ (874.5)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	Dec. 22, 2017	Jun. 30, 2020	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Line Items]
Statutory tax rate	21.00%
Tax cuts and jobs act, accounting complete			true
Income tax expense from revaluation of deferred tax assets and liabilities			$ 0.4
Additional income tax expense from transition tax provisional liability			$ 3.7
Decrease in transition tax reserve based on adjustments to expected post-1986 deferred foreign income		$ 16.4
Operating Loss Carryforwards				$ 2.6	$ 4
Deferred income tax assets:
Federal and foreign net operating loss carryforwards				188.3	173.5
Deferred income tax liabilities:
Operating Loss Carryforwards				2.6	4
Undistributed Foreign Earnings				1,700
Balance at end of fiscal year				206.7	224.3	$ 127.1	$ 148.9
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				189.5	207.5
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued				72.4	80
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense				6.6	9.7	$ 5.8
Decrease in Unrecognized Tax Benefits is Reasonably Possible				21.9
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards				1,795	1,638
Deferred income tax assets:
State net operating loss carryforwards				67	57.6
Tax Credit Carryforward, Deferred Tax Asset				79.4	69.5
Tax credit carryforward, valuation allowance				71.9	56.8
Deferred income tax liabilities:
Operating Loss Carryforwards				1,795	1,638
Operating Loss Carryforwards, Valuation Allowance				12.7	10.2
Foreign Country [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards				765.1	663.2
Deferred income tax assets:
Federal and foreign net operating loss carryforwards				187.7	172.5
Deferred income tax liabilities:
Operating Loss Carryforwards				765.1	663.2
Operating Loss Carryforwards, Valuation Allowance				$ 165.9	$ 144.1
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, 2022
Tax Credit Carryforward, Years to Expiration				5 years
Minimum [Member] | Foreign Country [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Oct. 1, 2022
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, 2040
Tax Credit Carryforward, Years to Expiration				10 years
Maximum [Member] | Foreign Country [Member]
Deferred income tax liabilities:
Operating loss carryforward expiration				Sep. 30, 2040

Income Taxes Effective Tax Rate

Income Taxes Effective Tax Rate Reconciliation (Details)		Dec. 22, 2017	Sep. 30, 2020		Sep. 30, 2019	Sep. 30, 2018
Statutory federal tax rate		21.00%
Continuing Operations [Member]
Statutory federal tax rate			21.00%	[1]	21.00%	24.50%
Foreign rate differential			(1.10%)	[1]	1.30%	0.60%
Adjustment and resolution of federal, state and foreign tax uncertainties			2.70%	[1]	1.20%	0.90%
State taxes, net of federal benefit			(1.30%)	[1]	2.50%	4.30%
Tax Act	[2]					(109.10%)
Excess tax benefit related to stock compensation			(0.50%)	[1]	(0.30%)	(0.80%)
Research and development and other tax credits, net of valuation allowances and reserves			3.70%	[1]	(0.70%)	(0.50%)
Income attributable to noncontrolling interest			0.10%	[1]	(0.10%)	(0.10%)
Domestic manufacturer’s deduction						(1.80%)
Change in valuation allowance			(4.10%)	[1]	0.20%	(1.80%)
Nondeductible transaction costs					1.00%
Goodwill impairment	[1]		(51.20%)
Nontaxable increased cash surrender value			1.30%	[1]	(0.60%)	(0.80%)
Withholding taxes			(0.70%)	[1]	0.60%	0.50%
Brazilian net worth deduction			1.70%	[1]	(0.90%)	(0.90%)
Other, net			(2.90%)	[1]	(1.00%)	0.50%
Effective tax rate			(31.30%)	[1]	24.20%	(84.50%)
[1]	The negative tax rate for fiscal year 2020 is the result of applying total income tax expense to the loss before income taxes. The signs within the table are consequently the opposite compared to prior year.
[2]	For the year ended September 30, 2018, 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, 2020	Sep. 30, 2019
Deferred income tax assets:
Accruals and allowances		$ 5.3	$ 10.7
Employee related accruals and allowances		121.3	125.1
Pension		60.5	96.8
State net operating loss carryforwards, net of federal benefit		67	57.6
State credit carryforwards, net of federal benefit		79.4	69.5
Federal and foreign net operating loss carryforwards		188.3	173.5
Restricted stock and options		33.7	39.3
Lease liabilities		179.1
Other		52.8	52.8
Deferred Tax Assets, Gross		787.4	625.3
Deferred income tax liabilities:
Property, plant and equipment		1,885.5	1,840.5
Deductible intangibles and goodwill		841.5	914.7
Inventory reserves		216.2	188.3
Deferred gain		272.2	275.2
Basis difference in joint ventures		33.8	33.1
Right-of-use assets		163.8
Deferred Tax Liabilities, Gross		3,413	3,251.8
Valuation allowances		257.5	218
Net deferred income tax liability		2,883.1	2,844.5
Long-term deferred tax asset	[1]	33.8	33.5
Long-term deferred tax liability		2,916.9	2,878
Net deferred income tax liability		$ 2,883.1	$ 2,844.5
[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, 2020	Sep. 30, 2019	Sep. 30, 2018
Movement in Deferred Tax Asset Valuation Allowance [Roll Forward]
Balance at beginning of fiscal year		$ 218	$ 229.4	$ 219.1
Increases		46.2	25.4	50.8
Allowances related to purchase accounting	[1]		0.8	0.1
Reductions		(6.7)	(37.6)	(40.6)
Balance at end of fiscal year		$ 257.5	$ 218	$ 229.4
[1]	Amounts in fiscal 2019 relate to the KapStone Acquisition. Amounts in fiscal 2018 relate to the MPS Acquisition.

Income Taxes Unrecognized Tax B

Income Taxes Unrecognized Tax Benefit (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of fiscal year		$ 224.3	$ 127.1	$ 148.9
Additions related to purchase accounting	[1]		1	3.4
Additions for tax positions taken in current year	[2]	5	103.8	3.1
Additions for tax positions taken in prior fiscal years		11.7	1.8	18
Reductions for tax positions taken in prior fiscal years	[2]	(16.7)	(0.5)	(5.3)
Reductions due to settlement	[3]		(4)	(29.4)
Reductions for currency translation adjustments		(8.8)	(1.7)	(9.6)
Reductions as a result of a lapse of the applicable statute of limitations		(8.8)	(3.2)	(2)
Balance at end of fiscal year		$ 206.7	$ 224.3	$ 127.1
[1]
[2]
[3]	Amounts in fiscal 2019 relate to the settlements of state and foreign audit examinations. 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 there was a reserve.

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2020USD ($)segment	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment				3
Insurance proceeds received, net cash used for investing activities				$ 6.5	$ 25.5	$ 7.9
Goodwill impairment loss	$ 1,333.2			1,333.2
Hurricane Michael [Member]
Segment Reporting Information [Line Items]
Insurance proceeds received		$ 70	$ 20
Corrugated Packaging [Member]
Segment Reporting Information [Line Items]
Pre-Tax Inventory Step-Up					24.7	$ 1
Corrugated Packaging [Member] | Grupo Gondi Investment [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	101.7	121.4		101.7	121.4
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Amortizable Portion	$ 41.9	$ 53.1		$ 41.9	53.1
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
Corrugated Packaging [Member] | Hurricane Michael [Member]
Segment Reporting Information [Line Items]
Insurance proceeds from business interruption recoveries				$ 11.7	55.3
Insurance proceeds for direct costs and property damage				20.6	124.7
Insurance proceeds received, net cash provided by operating activities				30.9	154.5
Insurance proceeds received, net cash used for investing activities				1.4	25.5
Corrugated Packaging [Member] | Hurricane Michael [Member] | Cost of Goods Sold [Member]
Segment Reporting Information [Line Items]
Insurance proceeds received				32.3	$ 180
Consumer Packaging [Member]
Segment Reporting Information [Line Items]
Goodwill impairment loss				$ 1,333.2

Segment Information - Schedule

Segment Information - Schedule of Revenue from External Customers, Segment Income and Long-Lived Assets, by Geographical Areas (Details) - Foreign Operations [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers, Segment Income and Long-Lived Assets [Line Items]
Net sales	$ 3,105.6	$ 3,332.4	$ 3,236.7
Segment income	298.2	392.3	360.7
Long-Lived Assets	$ 1,390.6	$ 1,466.4	$ 1,400.2
Percentage of Net Sales to Unaffiliated Customers	17.70%	18.20%	19.90%
Percentage of Segment Income	21.90%	21.90%	21.10%
Percentage of Long-Lived Assets	12.90%	13.10%	15.40%

Segment Information - Certain O

Segment Information - Certain Operating Data for Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net sales	$ 4,471.5	$ 4,236.3	$ 4,447.3	$ 4,423.7	$ 4,651.6	$ 4,690	$ 4,620	$ 4,327.4	$ 17,578.8	$ 18,289	$ 16,285.1
Gain on sale of certain closed facilities									15.6	52.6
Multiemployer pension withdrawal income (expense)		2	(0.9)		4.6	1.7			1.1	6.3	(184.2)
Land and Development impairments							(13)			(13)	(31.9)
Restructuring and other costs	(56.5)	(9.7)	(16.4)	$ (30.1)	(66.6)	(17.9)	(34.8)	(54.4)	(112.7)	(173.7)	(105.4)
Goodwill impairment	(1,333.2)								(1,333.2)
Interest expense, net									(393.5)	(431.3)	(293.8)
Loss on extinguishment of debt	(0.4)	$ (0.6)	$ (0.5)		(0.4)	$ (3.2)	$ 0.4	$ (1.9)	(1.5)	(5.1)	(0.1)
Other income, net									9.5	2.4	12.7
(Loss) income before income taxes									(522.6)	1,144.7	1,034.8
Depreciation, depletion and amortization									1,487	1,511.2	1,252.2
Identifiable assets	28,779.7				30,156.7				28,779.7	30,156.7	25,360.5
Goodwill	5,962.2				7,285.6				5,962.2	7,285.6	5,577.6	$ 5,528.3
Intangibles, net	3,667.2				4,059.5				3,667.2	4,059.5	3,122
Capital expenditures									978.1	1,369.1	999.9
Equity method investments	429.6				469.1				429.6	469.1	457.8
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									17,771.1	18,446.1	16,452.9
Segment income									1,362.8	1,790.2	1,707.6
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales									(192.3)	(157.1)	(167.8)
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Non-allocated expenses									(70.7)	(83.7)	(70.1)
Interest expense, net									(393.5)	(431.3)	(293.8)
Corrugated Packaging [Member]
Segment Reporting Information [Line Items]
Net sales									11,419.2	11,816.7
Depreciation, depletion and amortization									951.4	950.6	700.5
Identifiable assets	16,507				16,681.1				16,507	16,681.1	11,069.6
Goodwill	3,673.5				3,695				3,673.5	3,695	1,966.7	1,941.5
Intangibles, net	1,423				1,655.1				1,423	1,655.1	506.2
Capital expenditures									731.1	961.4	657.3
Equity method investments	414.3				457.1				414.3	457.1	455.6
Corrugated Packaging [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									11,419.2	11,816.7	9,693
Segment income									1,037.7	1,399.6	1,240
Corrugated Packaging [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales									(71)	(75.3)	(87.3)
Corrugated Packaging [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									11,348.2	11,741.4	9,605.7
Consumer Packaging [Member]
Segment Reporting Information [Line Items]
Net sales									6,333	6,606
Goodwill impairment									(1,333.2)
Depreciation, depletion and amortization									529.5	552.1	546.5
Identifiable assets	9,584.9				11,038.7				9,584.9	11,038.7	11,511.1
Goodwill	2,288.7				3,590.6				2,288.7	3,590.6	3,610.9	$ 3,586.8
Intangibles, net	2,244.2				2,404.4				2,244.2	2,404.4	2,615.8
Capital expenditures									217.1	365.9	308.3
Equity method investments	14.9				11.6				14.9	11.6	1.8
Consumer Packaging [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									6,333	6,606	6,617.5
Segment income									323.7	388.1	445.1
Consumer Packaging [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales									(121.3)	(81.8)	(80.5)
Consumer Packaging [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									6,211.7	6,524.2	6,537
Land and Development [Member]
Segment Reporting Information [Line Items]
Net sales									18.9	23.4
Depreciation, depletion and amortization											0.7
Identifiable assets					28.3					28.3	49.1
Land and Development [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									18.9	23.4	142.4
Segment income									1.4	2.5	22.5
Land and Development [Member] | Unaffiliated Customers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									18.9	23.4	142.4
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization									6.1	8.5	4.5
Identifiable assets	2,680.8				2,382.8				2,680.8	2,382.8	2,671.2
Capital expenditures									29.9	41.8	34.3
Equity method investments	0.4				0.4				0.4	0.4	0.4
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 7				$ 25.8				$ 7	$ 25.8	$ 59.5

Segment Information - Changes i

Segment Information - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year		$ 7,328.4	$ 5,620.4	$ 5,571.1
Accumulated impairment losses, beginning of period		(42.8)	(42.8)	(42.8)
Goodwill, beginning of fiscal year		7,285.6	5,577.6	5,528.3
Goodwill acquired			1,750.2	89.2
Goodwill impairment	$ (1,333.2)	(1,333.2)
Goodwill disposed of		(0.3)		(4.2)
Purchase price allocation adjustments		13.7	(0.5)	20.7
Translation adjustments		(3.6)		(56.4)
Translation and other adjustments			(41.7)
Goodwill, Gross end of fiscal year	7,338.2	7,338.2	7,328.4	5,620.4
Accumulated impairment losses, end of period	(1,376)	(1,376)	(42.8)	(42.8)
Goodwill, end of fiscal year	5,962.2	5,962.2	7,285.6	5,577.6
Corrugated Packaging [Member]
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year		3,695.1	1,966.8	1,941.6
Accumulated impairment losses, beginning of period		(0.1)	(0.1)	(0.1)
Goodwill, beginning of fiscal year		3,695	1,966.7	1,941.5
Goodwill acquired			1,746.4	65.4
Goodwill disposed of				(4.2)
Purchase price allocation adjustments		14.3	0.9	2.3
Translation adjustments		(35.8)		(38.3)
Translation and other adjustments			(19)
Goodwill, Gross end of fiscal year	3,673.6	3,673.6	3,695.1	1,966.8
Accumulated impairment losses, end of period	(0.1)	(0.1)	(0.1)	(0.1)
Goodwill, end of fiscal year	3,673.5	3,673.5	3,695	1,966.7
Consumer Packaging [Member]
Goodwill [Roll Forward]
Goodwill, Gross beginning of fiscal year		3,633.3	3,653.6	3,629.5
Accumulated impairment losses, beginning of period		(42.7)	(42.7)	(42.7)
Goodwill, beginning of fiscal year		3,590.6	3,610.9	3,586.8
Goodwill acquired			3.8	23.8
Goodwill impairment		(1,333.2)
Goodwill disposed of		(0.3)
Purchase price allocation adjustments		(0.6)	(1.4)	18.4
Translation adjustments		32.2		(18.1)
Translation and other adjustments			(22.7)
Goodwill, Gross end of fiscal year	3,664.6	3,664.6	3,633.3	3,653.6
Accumulated impairment losses, end of period	(1,375.9)	(1,375.9)	(42.7)	(42.7)
Goodwill, end of fiscal year	$ 2,288.7	$ 2,288.7	$ 3,590.6	$ 3,610.9

Interest Expense, Net - Summary

Interest Expense, Net - Summary of Components of Interest Expense, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Interest Income Expense Net [Abstract]
Interest expense	$ (465.5)	$ (489.4)	$ (352.8)
Interest income	72	58.1	59
Interest expense, net	$ (393.5)	$ (431.3)	$ (293.8)

Inventories - Schedule of Inven

Inventories - Schedule of Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Inventories [Abstract]
Finished goods and work in process	$ 844.2	$ 938.9
Raw materials	772.7	818.8
Supplies and spare parts	500.3	479.7
Inventories at FIFO cost	2,117.2	2,237.4
LIFO reserve	(93.8)	(129.9)
Net inventories	$ 2,023.4	$ 2,107.5

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 17,915.5	$ 17,461.3
Less: accumulated depreciation, depletion and amortization	(7,136.6)	(6,271.8)
Property, plant and equipment, net	10,778.9	11,189.5
Land and Buildings [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	2,524.7	2,442.3
Machinery and Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	15,147.3	14,743.6
Forestlands and Mineral Rights [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	110.8	144
Transportation Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	29.1	31.2
Leasehold Improvements [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 103.6	$ 100.2

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation	$ 1,054.9	$ 1,074.6	$ 923.8

Other Intangible Assets - Sched

Other Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	15 years 6 months
Gross Carrying Amount	$ 5,663.7	$ 5,654.3
Accumulated Amortization	$ (1,996.5)	(1,594.8)
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	15 years 6 months
Gross Carrying Amount	$ 5,418.1	5,395.5
Accumulated Amortization	$ (1,841.2)	(1,452.1)
Trademarks and Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	21 years 7 months 6 days
Gross Carrying Amount	$ 130.5	129.9
Accumulated Amortization	$ (65.7)	(55.3)
Favorable Contracts [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	7 years 2 months 12 days
Gross Carrying Amount	$ 44	57
Accumulated Amortization	$ (41.6)	(42.6)
Technology and Patents [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	11 years 4 months 24 days
Gross Carrying Amount	$ 37.5	39.2
Accumulated Amortization	$ (21.6)	(21.2)
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	8 years
Gross Carrying Amount	$ 26.5	25.7
Accumulated Amortization	$ (22.8)	(20.5)
Noncompete Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	2 years
Gross Carrying Amount	$ 3.4	3.4
Accumulated Amortization	$ (3.3)	(2.9)
Other [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Avg. Life (in years)	29 years 6 months
Gross Carrying Amount	$ 3.7	3.6
Accumulated Amortization	$ (0.3)	$ (0.2)

Other Intangible Assets - Estim

Other Intangible Assets - Estimated Intangible Asset Future Amortization Expense (Details) $ in Millions	Sep. 30, 2020USD ($)
Other Intangible Assets [Abstract]
Fiscal 2021	$ 356.8
Fiscal 2022	349.3
Fiscal 2023	343.1
Fiscal 2024	322.6
Fiscal 2025	$ 308

Other Intangible Assets - Addit

Other Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Other Intangible Assets [Abstract]
Intangible Assets Amortization Expense	$ 405.4	$ 408	$ 300.8
Other Intangible Assets Amortization Expense	$ 26.7	$ 28.6	$ 27.6

Fair Value - Additional Informa

Fair Value - Additional Information (Details) - USD ($) $ in Millions	Sep. 25, 2018	Sep. 30, 2020	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 17, 2020	Sep. 19, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Maximum eligible receivables that may be sold	$ 550						$ 700	$ 650
Non-cash transaction to repurchase receivables previously sold to financial institution	$ 424.8
Receivables sold under A/R Sales Agreement		$ 589.4		$ 589.4	$ 592.6
Estimated loss on sale of accounts receivable in a fiscal year				12.7	17.3	$ 11.2
Goodwill impairment loss		$ 1,333.2		1,333.2
Land and Development impairments			$ 13		13	31.9
Mineral Rights [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Land and Development impairments					$ 13	23.6
Real Estate [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Land and Development impairments						8.3
Real Estate [Member] | Mineral Rights [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Land and Development impairments						$ 31.9
Consumer Packaging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Goodwill impairment loss				$ 1,333.2

Fair Value - Summary of Activit

Fair Value - Summary of Activity Under A/R Sales Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Receivables sold to the financial institution and derecognized	$ 2,446.2	$ 2,051.6
Receivables collected by financial institution	(2,449.4)	(1,971.1)
Cash proceeds from financial institution	$ 3.2	$ (80.5)

Debt - Additional Information (

Debt - Additional Information (Details)

Jun. 01, 2020USD ($)

Nov. 21, 2019USD ($)

Oct. 25, 2019

Sep. 27, 2019USD ($)

Jun. 07, 2019USD ($)

May 16, 2019USD ($)

May 02, 2019USD ($)

Apr. 10, 2019BRL (R$)Drawdown

Feb. 26, 2019

Dec. 07, 2018USD ($)

Dec. 03, 2018USD ($)

Oct. 29, 2018

Apr. 27, 2018EUR (€)

Mar. 07, 2018USD ($)

Mar. 06, 2018USD ($)

Aug. 24, 2017USD ($)

Mar. 31, 2018USD ($)

Oct. 31, 2017USD ($)

Sep. 30, 2020USD ($)

Sep. 30, 2019USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2020BRL (R$)

Nov. 20, 2019USD ($)

Oct. 01, 2019USD ($)Mill

Sep. 30, 2019BRL (R$)

Jul. 01, 2015USD ($)

Debt Instrument [Line Items]

Weighted average interest rate excluding fair value step-up

3.90%

3.90%

Unamortized fair market value step-up

$ 208,900,000

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

11 years 6 months

Letters of credit outstanding, amount

$ 62,900,000

Fair value of debt

10,400,000,000

$ 10,600,000,000

Amortization of debt issuance costs

8,200,000

7,800,000

$ 6,300,000

Repayment of debt

$ 1,449,200,000

$ 5,631,600,000

$ 2,032,900,000

Debt, Weighted Average Interest Rate

3.80%

4.00%

3.80%

4.00%

DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 3,800,000,000

Debt instrument, interest rate description

On February 26, 2019, we amended the Delayed Draw Credit Agreement. The applicable interest rate margin for the 5-year term loan is now 1.000% to 1.950% for LIBOR rate loans and 0.000% to 0.950% for alternate base rate loans.

Foreign Exchange Contract [Member]

Debt Instrument [Line Items]

Amount of foreign exchange contracts

$ 250,200,000

$ 351,000,000

Unsecured Debt [Member]

Debt Instrument [Line Items]

Prepayment of outstanding principal amount

$ 600,000,000

Chip Mills [Member]

Debt Instrument [Line Items]

Number of mills recharacterized short-term and long-term liability | Mill

2

Finance lease obligation reclassified from short term and long term liability

$ 100,300,000

Receivables Securitization Facility [Member]

Debt Instrument [Line Items]

Repayment of debt

$ 100,000,000

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

Debt Instrument [Line Items]

Long-term debt

0

0

Debt instrument, maximum borrowing capacity, amount

700,000,000

592,100,000

Receivables backed financing, maximum borrowing amount

$ 700,000,000

Debt instrument, maturity date

Jul. 22, 2019

Loans and Leases Receivable, Collateral for Secured Borrowings

$ 1,128,300,000

$ 959,300,000

Debt instrument, amended maturity date

May 2, 2022

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%

0.25%

0.25%

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

Debt Instrument [Line Items]

Applicable margin

0.80%

Variable rate basis

one month LIBOR

Public Bond Obligations [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

$ 7,000,000,000

$ 6,500,000,000

Revolving Credit Facility [Member] | Non-U.S. Dollar Currencies [Member]

Debt Instrument [Line Items]

Capacity available for special purpose

$ 400,000,000

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

$ 2,300,000,000

$ 2,000,000,000

Credit facility, maturity date

Nov. 21, 2024

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

Debt Instrument [Line Items]

Applicable margin

1.125%

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

Debt Instrument [Line Items]

Applicable margin

0.125%

Revolving Credit Facility [Member] | Unsecured Debt [Member] | Non-U.S. Dollar Currencies [Member]

Debt Instrument [Line Items]

Capacity available for special purpose

$ 500,000,000

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

Debt Instrument [Line Items]

Credit facility, maximum permitted debt to capitalization ratio

0.65

0.60

Facility commitment

0.30%

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

Debt Instrument [Line Items]

Applicable margin

1.75%

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

Debt Instrument [Line Items]

Applicable margin

0.75%

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

Debt Instrument [Line Items]

Facility commitment

0.125%

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

Debt Instrument [Line Items]

Applicable margin

1.00%

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

Debt Instrument [Line Items]

Applicable margin

0.00%

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

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 200,000,000

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

Debt Instrument [Line Items]

Capacity available for special purpose

$ 150,000,000

Long-Term Committed Credit Facilities [Member] | Cash and Cash Equivalents [Member]

Debt Instrument [Line Items]

Line of credit facility, remaining borrowing capacity

$ 3,600,000,000

Senior Notes due 2033 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.00%

Debt instrument, aggregate principal amount

$ 600,000,000

Debt instrument, maturity year

2033

Debt instrument, transaction closing date

Jun. 3, 2020

Notes due June 2020 [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

9.75%

Prepayment of outstanding principal amount

$ 100,000,000

Senior Notes due June 2028 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.90%

Debt instrument, aggregate principal amount

$ 500,000,000

Debt instrument, maturity year

2028

Senior Notes due 2032 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

4.20%

Debt instrument, aggregate principal amount

$ 500,000,000

Debt instrument, maturity year

2032

Senior Notes due 2026 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

4.65%

Debt instrument, aggregate principal amount

$ 750,000,000

Debt instrument, maturity year

2026

Senior Notes due 2026 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

749,300,000

Senior Notes due 2029 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

4.90%

Debt instrument, aggregate principal amount

$ 750,000,000

Debt instrument, maturity year

2029

Senior Notes due 2029 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

750,000,000

Senior Notes due 2025 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.75%

Debt instrument, aggregate principal amount

$ 600,000,000

Debt instrument, maturity year

2025

Senior Notes due 2025 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

600,000,000

Senior Notes due 2028 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

4.00%

Debt instrument, aggregate principal amount

$ 600,000,000

Debt instrument, maturity year

2028

Senior Notes due 2028 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

$ 590,000,000

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

1.90%

3.30%

1.90%

3.30%

Commercial Paper [Member]

Debt Instrument [Line Items]

Repayment of debt

445,000,000

Commercial Paper [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term debt

$ 250,000,000

Debt, Weighted Average Interest Rate

2.39%

2.39%

Borrowings outstanding

$ 0

$ 339,200,000

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

$ 1,000,000,000

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

Other Credit Facility [Member]

Debt Instrument [Line Items]

Repayment of debt

$ 104,700,000

Senior Notes due 2024 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.00%

Debt instrument, aggregate principal amount

$ 500,000,000

Debt instrument, maturity year

2024

Senior Notes due 2024 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

490,000,000

Senior Notes due 2027 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate

3.375%

Debt instrument, aggregate principal amount

$ 500,000,000

Debt instrument, maturity year

2027

Senior Notes due 2027 [Member] | Tendered and Exchanged Notes [Member]

Debt Instrument [Line Items]

Debt instrument, aggregate principal amount

491,000,000

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

Debt Instrument [Line Items]

Long-term debt

598,700,000

598,600,000

Debt Instrument, Term, in Years

7 years

Credit Facility, maximum borrowing capacity

$ 600,000,000

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

Debt Instrument [Line Items]

Credit facility, amount of potential increase to the principal amount

$ 300,000,000

Bank of America Five Year Term Loan [Member]

Debt Instrument [Line Items]

Long-term debt

$ 300,000,000

300,000,000

Credit Facility, maximum borrowing capacity

$ 300,000,000

Credit facility, maturity date

Jun. 7, 2024

Debt instrument, maturity period

5 years

Debt instrument, interest rate description

The applicable interest rate margin was initially 0.825% to 1.750% per annum for LIBOR rate loans and 0.000% to 0.750% per annum for alternate base rate loans, in each case depending on the Leverage Ratio (as defined in the credit agreement) or our corporate credit ratings, whichever yields a lower applicable interest rate margin, at such time.

Bank of America Five Year Term Loan [Member] | Maximum [Member] | LIBOR [Member]

Debt Instrument [Line Items]

Applicable margin

1.75%

Bank of America Five Year Term Loan [Member] | Maximum [Member] | Base Rate [Member]

Debt Instrument [Line Items]

Applicable margin

0.75%

Bank of America Five Year Term Loan [Member] | Minimum [Member] | LIBOR [Member]

Debt Instrument [Line Items]

Applicable margin

0.825%

Bank of America Five Year Term Loan [Member] | Minimum [Member] | Base Rate [Member]

Debt Instrument [Line Items]

Applicable margin

0.00%

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

Debt Instrument [Line Items]

Long-term debt

$ 250,000,000

350,000,000

Credit Facility, maximum borrowing capacity | €

€ 500,000,000

Credit facility, maturity date

Nov. 21, 2022

Apr. 27, 2021

Debt instrument, maturity period

3 years

Incremental line of credit | €

€ 100,000,000

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

€ 500,000,000

Current portion of long-term debt

$ 175,000,000

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

Debt Instrument [Line Items]

Amount of foreign exchange contracts

250,200,000

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

Debt Instrument [Line Items]

Credit Facility, maximum borrowing capacity

$ 450,000,000

Debt instrument, maturity period

364 days

364 days

364 days

Debt, Weighted Average Interest Rate

3.17%

3.17%

Borrowings outstanding

$ 0

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

Debt Instrument [Line Items]

Long-term debt

$ 0

Credit Facility, maximum borrowing capacity

$ 300,000,000

Debt instrument, maturity period

364 days

364 days

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

Debt Instrument [Line Items]

Long-term debt

$ 0

Credit Facility, maximum borrowing capacity

$ 1,750,000,000

Debt instrument, maturity period

3 years

3 years

Five Year Term Loan | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Long-term debt

648,900,000

$ 1,396,900,000

Credit Facility, maximum borrowing capacity

$ 1,750,000,000

Prepayment of outstanding principal amount

$ 750,000,000

Debt instrument, maturity period

5 years

5 years

5 years

5 years

Five Year Term Loan | Maximum [Member] | LIBOR [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

1.95%

Five Year Term Loan | Maximum [Member] | Base Rate [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

0.95%

Five Year Term Loan | Minimum [Member] | LIBOR [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

1.00%

Five Year Term Loan | Minimum [Member] | Base Rate [Member] | DDTL Credit Agreement [Member]

Debt Instrument [Line Items]

Applicable margin

0.00%

Brazil Delayed Draw Credit Facilities [Member] | Unsecured Debt [Member]

Debt Instrument [Line Items]

Long-term debt | R$

R$ 695100000

R$ 199500000

Credit Facility, maximum borrowing capacity | R$

R$ 750000000.0

Credit facility, maturity date

Apr. 10, 2024

Incremental line of credit | R$

R$ 250000000.0

Credit facility initial drowdowns period

18 months

Number of drawdowns under credit facility | Drawdown

10

Amount of incremental drawdowns | R$

R$ 50000000.0

Credit facility semiannual installments repayment beginning date

Apr. 10, 2021

Credit facility basis spread on floating rate

1.50%

Percentage of fee paid on unused credit facility

0.45%

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, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Total debt	$ 9,430.6	$ 10,063.4
Less: current portion of debt	222.9	561.1
Long-term debt due after one year	$ 9,207.7	$ 9,502.3
Debt, Weighted Average Interest Rate	3.80%	4.00%
Notes Due Fiscal 2020 to 2022 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 399.3	$ 507.8
Debt, Weighted Average Interest Rate	5.00%	4.90%
Notes Due Fiscal 2023 to 2028 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 3,773.6	$ 3,769.1
Debt, Weighted Average Interest Rate	4.00%	4.00%
Notes Due Fiscal 2029 to 2033 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 2,778.9	$ 2,197.6
Debt, Weighted Average Interest Rate	4.50%	4.90%
Notes Due Fiscal 2037 to 2047 [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 178.6	$ 179
Debt, Weighted Average Interest Rate	6.20%	6.20%
Term Loan Facilities [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 1,547.6	$ 2,295.5
Debt, Weighted Average Interest Rate	1.90%	3.30%
Revolving Credit and Swing Facilities [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 250	$ 396
Debt, Weighted Average Interest Rate	1.10%	2.90%
Commercial Paper [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt		$ 339.2
Debt, Weighted Average Interest Rate		2.39%
Finance Lease Obligations [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 274.8	$ 185.8
Debt, Weighted Average Interest Rate	4.00%	4.30%
Vendor Financing and Commercial Card Programs [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 89.8	$ 123.2
International and Other Debt [Member]
Debt Instrument [Line Items]
Total debt	$ 138	$ 70.2
Debt, Weighted Average Interest Rate	3.10%	6.60%

Debt - Schedule of Aggregate Ma

Debt - Schedule of Aggregate Maturities of Debt (Details) - Long-term Debt, Excluding Finance Lease Obligations [Member] $ in Millions	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
Fiscal 2021	$ 214.2
Fiscal 2022	438.7
Fiscal 2023	639.1
Fiscal 2024	1,386.8
Fiscal 2025	600
Thereafter	5,729.1
Fair value of debt step-up, deferred financing costs and unamortized bond discounts	147.9
Total	$ 9,155.8

Selected Condensed Consolidat_3

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Condensed Consolidating Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Condensed Income Statements Captions [Line Items]
Net sales	$ 4,471.5	$ 4,236.3	$ 4,447.3	$ 4,423.7	$ 4,651.6	$ 4,690	$ 4,620	$ 4,327.4	$ 17,578.8	$ 18,289	$ 16,285.1
Cost of goods sold									14,381.6	14,540	12,923.1
Gross profit	813.4	770	804.8	809	1,078.7	988.9	899.6	781.8	3,197.2	3,749	3,362
Selling, general and administrative, excluding intangible amortization									1,624.4	1,715.2	1,546.6
Selling, general and administrative intangible amortization									400.5	400.2	296.6
Loss (gain) on disposal of assets	(10.4)	1	(5.6)	(1.3)	(3.9)	6.5		(43.8)	(16.3)	(41.2)	10.1
Multiemployer pension withdrawal (income) expense		(2)	0.9		(4.6)	(1.7)			(1.1)	(6.3)	184.2
Land and Development impairments							13			13	31.9
Restructuring and other costs	56.5	9.7	16.4	30.1	66.6	17.9	34.8	54.4	112.7	173.7	105.4
Goodwill impairment	1,333.2								1,333.2
Operating (loss) profit									(256.2)	1,494.4	1,187.2
Interest expense, net									(393.5)	(431.3)	(293.8)
(Loss) gain on extinguishment of debt	(0.4)	(0.6)	(0.5)		(0.4)	(3.2)	0.4	(1.9)	(1.5)	(5.1)	(0.1)
Pension and other postretirement non-service (expense) income									103.3	74.2	95.3
Other income (expense), net									9.5	2.4	12.7
Equity in income of unconsolidated entities									15.8	10.1	33.5
(Loss) income before income taxes									(522.6)	1,144.7	1,034.8
Income tax benefit (expense)	(40)	(19.2)	(57.8)	(46.5)	(89.3)	(77.6)	(47.2)	(62.7)	(163.5)	(276.8)	874.5
Consolidated net (loss) income	(1,154.5)	180	148.9	139.5	312.4	253.8	161.9	139.8	(686.1)	867.9	1,909.3
Less: Net income attributable to noncontrolling interests									(4.8)	(5)	(3.2)
Net (loss) income attributable to common stockholders	$ (1,156)	$ 178.5	$ 148.1	$ 138.5	$ 310.8	$ 252.6	$ 160.4	$ 139.1	(690.9)	862.9	1,906.1
Comprehensive (loss) income attributable to common stockholders									(868.2)	489	1,668.1
Parent [Member]
Condensed Income Statements Captions [Line Items]
Interest expense, net											(12.5)
(Loss) gain on extinguishment of debt											(0.2)
Other income (expense), net									0.1
Equity in (loss) income of consolidated entities									(691)	862.9
(Loss) income before income taxes									(690.9)	862.9	(12.7)
Income tax benefit (expense)											3.1
Consolidated net (loss) income									(690.9)	862.9	(9.6)
Net (loss) income attributable to common stockholders									(690.9)	862.9	(9.6)
Comprehensive (loss) income attributable to common stockholders									(868.2)	489	(9.6)
Issuer [Member]
Condensed Income Statements Captions [Line Items]
Selling, general and administrative, excluding intangible amortization									2.8	(0.9)	1.5
Multiemployer pension withdrawal (income) expense										(0.2)	6.5
Restructuring and other costs									4.6	7.6	8.7
Operating (loss) profit									(7.4)	(6.5)	(16.7)
Interest expense, net									(250.1)	(246.8)	(76.9)
Intercompany interest (expense) income, net									(10.2)	(3.2)	28.1
(Loss) gain on extinguishment of debt									(1.4)	(3)	(1.4)
Other income (expense), net									0.2	(5.1)	0.7
Equity in (loss) income of consolidated entities									(343.2)	1,157.3	1,962
(Loss) income before income taxes									(612.1)	892.7	1,895.8
Income tax benefit (expense)									77.7	67.9	19.9
Consolidated net (loss) income									(534.4)	960.6	1,915.7
Net (loss) income attributable to common stockholders									(534.4)	960.6	1,915.7
Comprehensive (loss) income attributable to common stockholders									(711)	588	1,677.7
Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales									2,430.9	2,543.8	2,593
Cost of goods sold									1,916.7	2,026	2,004.2
Gross profit									514.2	517.8	588.8
Selling, general and administrative, excluding intangible amortization									101.2	120	94.1
Selling, general and administrative intangible amortization									99.5	104.4	104.2
Loss (gain) on disposal of assets									(0.1)	0.1	0.2
Multiemployer pension withdrawal (income) expense									(1.9)	(0.3)	12.5
Restructuring and other costs										0.3	5.6
Goodwill impairment									746.9
Operating (loss) profit									(431.4)	293.3	372.2
Interest expense, net									(137.9)	(163.4)	(173.5)
Intercompany interest (expense) income, net									(80.7)	(115.3)	(87.6)
(Loss) gain on extinguishment of debt										(1.9)	1.9
Pension and other postretirement non-service (expense) income									(6.9)	(6.5)	(6.9)
Other income (expense), net									(82.6)	3.4	(22.5)
Equity in income of unconsolidated entities											7.5
Equity in (loss) income of consolidated entities									228.6	736.5	1,343.8
(Loss) income before income taxes									(510.9)	746.1	1,434.9
Income tax benefit (expense)									11.4	7.2	131.8
Consolidated net (loss) income									(499.5)	753.3	1,566.7
Net (loss) income attributable to common stockholders									(499.5)	753.3	1,566.7
Comprehensive (loss) income attributable to common stockholders									(677.1)	389.4	1,351.4
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements Captions [Line Items]
Net sales									17,740.7	18,364.4	16,345.4
Cost of goods sold									15,026.1	15,114.2	13,572.2
Gross profit									2,714.6	3,250.2	2,773.2
Selling, general and administrative, excluding intangible amortization									1,520.4	1,596.1	1,451
Selling, general and administrative intangible amortization									301	295.8	192.4
Loss (gain) on disposal of assets									(16.2)	(41.3)	9.9
Multiemployer pension withdrawal (income) expense									0.8	(5.8)	165.2
Land and Development impairments										13	31.9
Restructuring and other costs									108.1	165.8	91.1
Goodwill impairment									586.3
Operating (loss) profit									214.2	1,226.6	831.7
Interest expense, net									(5.5)	(21.1)	(30.9)
Intercompany interest (expense) income, net									59.3	99.5	59.5
(Loss) gain on extinguishment of debt									(0.1)	(0.2)	(0.4)
Pension and other postretirement non-service (expense) income									110.2	80.7	102.2
Other income (expense), net									91.8	4.1	34.5
Equity in income of unconsolidated entities									15.8	10.1	26
(Loss) income before income taxes									485.7	1,399.7	1,022.6
Income tax benefit (expense)									(252.6)	(351.9)	719.7
Consolidated net (loss) income									233.1	1,047.8	1,742.3
Less: Net income attributable to noncontrolling interests									(4.8)	(5)	(3.2)
Net (loss) income attributable to common stockholders									228.3	1,042.8	1,739.1
Comprehensive (loss) income attributable to common stockholders									51.4	682.4	1,498.6
Eliminations [Member]
Condensed Income Statements Captions [Line Items]
Net sales									(2,592.8)	(2,619.2)	(2,653.3)
Cost of goods sold									(2,561.2)	(2,600.2)	(2,653.3)
Gross profit									(31.6)	(19)
Operating (loss) profit									(31.6)	(19)
Intercompany interest (expense) income, net									31.6	19
Equity in (loss) income of consolidated entities									805.6	(2,756.7)	(3,305.8)
(Loss) income before income taxes									805.6	(2,756.7)	(3,305.8)
Consolidated net (loss) income									805.6	(2,756.7)	(3,305.8)
Net (loss) income attributable to common stockholders									805.6	(2,756.7)	(3,305.8)
Comprehensive (loss) income attributable to common stockholders									$ 1,336.7	$ (1,659.8)	$ (2,850)

Selected Condensed Consolidat_4

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 251.1	$ 151.6
Accounts receivable	2,142.7	2,193.2
Inventories	2,023.4	2,107.5
Other current assets	520.5	496.2
Assets held for sale	7	25.8
Total current assets	4,944.7	4,974.3
Accounts receivable (net of allowances of $66.3 and $53.2)	2,142.7	2,193.2
Property, plant and equipment, net	10,778.9	11,189.5
Goodwill	5,962.2	7,285.6	$ 5,577.6	$ 5,528.3
Intangibles, net	3,667.2	4,059.5	3,122
Restricted assets held by special purpose entities	1,267.5	1,274.3
Prepaid pension asset	368.7	224.7
Other assets	1,790.5	1,148.8
Total assets	28,779.7	30,156.7	25,360.5
Current liabilities:
Current portion of debt	222.9	561.1
Accounts payable	1,674.2	1,831.8
Accrued compensation and benefits	386.7	470.4
Other current liabilities	645.1	571.8
Total current liabilities	2,928.9	3,435.1
Long-term debt due after one year	9,207.7	9,502.3
Pension liabilities, net of current portion	305.2	294
Postretirement benefit liabilities, net of current portion	145.4	162.1
Non-recourse liabilities held by special purpose entities	1,136.5	1,145.2
Deferred income taxes	2,916.9	2,878
Other long-term liabilities	1,490.3	1,053.9
Redeemable noncontrolling interests	1.3	1.9
Total stockholders’ equity	10,630.6	11,669.9	11,469.4
Noncontrolling interests	16.9	14.3
Total equity	10,647.5	11,684.2	$ 11,482.4
Total liabilities and equity	28,779.7	30,156.7
Parent [Member]
Current assets:
Other current assets	0.5
Total current assets	0.5
Investments in consolidated subsidiaries	11,070.4	11,973.6
Total assets	11,070.9	11,973.6
Current liabilities:
Accrued compensation and benefits	0.1	0.3
Intercompany payables	440.2	303.4
Total current liabilities	440.3	303.7
Total stockholders’ equity	10,630.6	11,669.9
Total equity	10,630.6	11,669.9
Total liabilities and equity	11,070.9	11,973.6
Issuer [Member]
Current assets:
Other current assets		1.2
Intercompany receivables	3	227.7
Total current assets	3	228.9
Intercompany notes receivable	168.8	155
Investments in consolidated subsidiaries	17,829.4	18,524.2
Other assets	63.6	67.8
Total assets	18,064.8	18,975.9
Current liabilities:
Current portion of debt	99.8	135.3
Accounts payable	1.9	0.7
Other current liabilities	27.1	18.6
Intercompany payables	643.6
Total current liabilities	772.4	154.6
Long-term debt due after one year	6,108.3	6,608
Intercompany notes payable	753.3	636.3
Other long-term liabilities	13	12.9
Total stockholders’ equity	10,417.8	11,564.1
Total equity	10,417.8	11,564.1
Total liabilities and equity	18,064.8	18,975.9
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	105.7	17.8
Accounts receivable	41.6	31.1
Inventories	175.3	254.3
Other current assets	11.6	11.8
Intercompany receivables	1.5
Total current assets	335.7	315
Accounts receivable (net of allowances of $66.3 and $53.2)	41.6	31.1
Property, plant and equipment, net	15.2	18.9
Goodwill	411.7	1,158.6
Intangibles, net	1,385.5	1,485
Intercompany notes receivable	141.1	156.9
Investments in consolidated subsidiaries	19,685.2	20,103.6
Other assets	220.8	185.3
Total assets	22,195.2	23,423.3
Current liabilities:
Current portion of debt		108.9
Accounts payable	27.7	31.3
Accrued compensation and benefits	10.2	14.5
Other current liabilities	71	83.8
Intercompany payables	440.8	1,052.9
Total current liabilities	549.7	1,291.4
Long-term debt due after one year	1,968.3	1,982.9
Intercompany notes payable	2,068	2,390.5
Pension liabilities, net of current portion	149.7	147.6
Postretirement benefit liabilities, net of current portion	25.9	25.7
Deferred income taxes	221.1	278.9
Other long-term liabilities	147.1	131.2
Total stockholders’ equity	17,065.4	17,175.1
Total equity	17,065.4	17,175.1
Total liabilities and equity	22,195.2	23,423.3
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	145.4	133.8
Accounts receivable	2,152	2,201.7
Inventories	1,848.1	1,853.2
Other current assets	508.4	483.2
Intercompany receivables	1,798.6	1,128.6
Assets held for sale	7	25.8
Total current assets	6,459.5	5,826.3
Accounts receivable (net of allowances of $66.3 and $53.2)	2,152	2,201.7
Property, plant and equipment, net	10,763.7	11,170.6
Goodwill	5,550.5	6,127
Intangibles, net	2,281.7	2,574.5
Restricted assets held by special purpose entities	1,267.5	1,274.3
Prepaid pension asset	368.7	224.7
Intercompany notes receivable	2,821.3	3,026.8
Other assets	1,565.5	971.8
Total assets	31,078.4	31,196
Current liabilities:
Current portion of debt	123.1	316.9
Accounts payable	1,695.5	1,839.4
Accrued compensation and benefits	376.4	455.6
Other current liabilities	547	469.4
Intercompany payables	278.5
Total current liabilities	3,020.5	3,081.3
Long-term debt due after one year	1,131.1	911.4
Intercompany notes payable	309.9	311.9
Pension liabilities, net of current portion	155.5	146.4
Postretirement benefit liabilities, net of current portion	119.5	136.4
Non-recourse liabilities held by special purpose entities	1,136.5	1,145.2
Deferred income taxes	2,755.2	2,675.2
Other long-term liabilities	1,330.2	909.8
Redeemable noncontrolling interests	1.3	1.9
Total stockholders’ equity	21,101.8	21,862.2
Noncontrolling interests	16.9	14.3
Total equity	21,118.7	21,876.5
Total liabilities and equity	31,078.4	31,196
Eliminations [Member]
Current assets:
Accounts receivable	(50.9)	(39.6)
Intercompany receivables	(1,803.1)	(1,356.3)
Total current assets	(1,854)	(1,395.9)
Accounts receivable (net of allowances of $66.3 and $53.2)	(50.9)	(39.6)
Intercompany notes receivable	(3,131.2)	(3,338.7)
Investments in consolidated subsidiaries	(48,585)	(50,601.4)
Other assets	(59.4)	(76.1)
Total assets	(53,629.6)	(55,412.1)
Current liabilities:
Accounts payable	(50.9)	(39.6)
Intercompany payables	(1,803.1)	(1,356.3)
Total current liabilities	(1,854)	(1,395.9)
Intercompany notes payable	(3,131.2)	(3,338.7)
Deferred income taxes	(59.4)	(76.1)
Total stockholders’ equity	(48,585)	(50,601.4)
Total equity	(48,585)	(50,601.4)
Total liabilities and equity	$ (53,629.6)	$ (55,412.1)

Selected Condensed Consolidat_5

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Condensed Consolidating Statements of Cash Flows (Details) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net cash provided by (used for) operating activities	$ 2,070,700,000	$ 2,310,200,000	$ 1,931,200,000
Investing activities:
Capital expenditures	(978,100,000)	(1,369,100,000)	(999,900,000)
Cash paid for purchase of businesses, net of cash acquired		(3,374,200,000)	(239,900,000)
Cash receipts on sold trade receivables			461,600,000
Investment in unconsolidated entities	(1,300,000)	(11,200,000)	(114,300,000)
Proceeds from sale of property, plant and equipment	35,000,000	119,100,000	23,300,000
Proceeds from property, plant and equipment insurance settlement	6,500,000	25,500,000	7,900,000
Other	16,400,000	30,300,000	46,200,000
Net cash used for investing activities	(921,500,000)	(4,579,600,000)	(815,100,000)
Financing activities:
Proceeds from issuance of notes	598,600,000	2,498,200,000	1,197,300,000
Additions to revolving credit facilities	428,000,000	222,200,000	702,400,000
Repayments of revolving credit facilities	(528,200,000)	(227,200,000)	(572,200,000)
Additions to debt	696,400,000	5,061,600,000	855,200,000
Repayments of debt	(1,449,200,000)	(5,631,600,000)	(2,032,900,000)
Changes in commercial paper, net	(339,200,000)	339,200,000
Other financing (repayments) additions	(80,300,000)	52,200,000	(269,900,000)
Issuances of common stock, net of related minimum tax withholdings	22,200,000	18,300,000	26,600,000
Purchases of common stock	0	(88,600,000)	(195,100,000)
Cash dividends paid to stockholders	(344,500,000)	(467,900,000)	(440,900,000)
Cash distributions paid to noncontrolling interests	(2,400,000)	(4,300,000)	(33,300,000)
Other	(22,500,000)	8,100,000	7,700,000
Net cash (used for) provided by financing activities	(1,021,100,000)	1,780,200,000	(755,100,000)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(28,600,000)	4,000,000	(28,200,000)
Increase (decrease) in cash, cash equivalents and restricted cash	99,500,000	(485,200,000)	332,800,000
Cash, cash equivalents and restricted cash at beginning of period	151,600,000	636,800,000	304,000,000
Cash, cash equivalents and restricted cash at end of period	251,100,000	151,600,000	636,800,000
Parent [Member]
Operating activities:
Net cash provided by (used for) operating activities	322,300,000	538,200,000	4,100,000
Investing activities:
Intercompany capital investment		(563,000,000)
Net cash used for investing activities		(563,000,000)
Financing activities:
Repayments of debt			(100,000)
Issuances of common stock, net of related minimum tax withholdings	22,200,000	18,300,000
Purchases of common stock		(88,600,000)
Cash dividends paid to stockholders	(344,500,000)	(467,900,000)
Intercompany capital receipt		563,000,000
Other			(4,000,000)
Net cash (used for) provided by financing activities	(322,300,000)	24,800,000	(4,100,000)
Issuer [Member]
Operating activities:
Net cash provided by (used for) operating activities	540,500,000	(203,800,000)	563,400,000
Investing activities:
Proceeds from property, plant and equipment insurance settlement	1,500,000
Intercompany notes proceeds		9,300,000
Intercompany capital investment		(563,000,000)	(2,000,000)
Net cash used for investing activities	1,500,000	(553,700,000)	(2,000,000)
Financing activities:
Proceeds from issuance of notes	598,600,000	2,498,200,000	1,197,300,000
Additions to revolving credit facilities	350,000,000	67,200,000
Repayments of revolving credit facilities	(350,000,000)	(67,200,000)
Additions to debt		4,101,800,000	2,700,000
Repayments of debt	(750,000,000)	(2,400,000,000)	(1,025,200,000)
Changes in commercial paper, net	(339,200,000)	339,200,000
Other financing (repayments) additions	(46,000,000)	46,000,000	(106,700,000)
Issuances of common stock, net of related minimum tax withholdings			26,600,000
Purchases of common stock			(195,100,000)
Cash dividends paid to stockholders			(440,900,000)
Intercompany notes payments		(3,800,000,000)
Other	(5,400,000)	(27,900,000)	(19,900,000)
Net cash (used for) provided by financing activities	(542,000,000)	757,300,000	(561,200,000)
Increase (decrease) in cash, cash equivalents and restricted cash		(200,000)	200,000
Cash, cash equivalents and restricted cash at beginning of period		200,000
Cash, cash equivalents and restricted cash at end of period			200,000
Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided by (used for) operating activities	171,100,000	442,100,000	375,800,000
Investing activities:
Capital expenditures			(1,200,000)
Proceeds from sale of property, plant and equipment	100,000
Proceeds from property, plant and equipment insurance settlement	1,300,000
Intercompany notes issued		(100,000)	(1,400,000)
Intercompany notes proceeds	5,700,000	6,700,000	4,500,000
Intercompany return of capital			82,600,000
Other	14,700,000	30,200,000	18,600,000
Net cash used for investing activities	21,800,000	36,800,000	103,100,000
Financing activities:
Repayments of debt	(105,000,000)	(957,500,000)	(22,500,000)
Other financing (repayments) additions			(8,900,000)
Intercompany notes borrowing		75,700,000
Intercompany notes payments		(70,100,000)
Net cash (used for) provided by financing activities	(105,000,000)	(951,900,000)	(31,400,000)
Increase (decrease) in cash, cash equivalents and restricted cash	87,900,000	(473,000,000)	447,500,000
Cash, cash equivalents and restricted cash at beginning of period	17,800,000	490,800,000	43,300,000
Cash, cash equivalents and restricted cash at end of period	105,700,000	17,800,000	490,800,000
Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided by (used for) operating activities	1,036,800,000	1,533,700,000	1,016,300,000
Investing activities:
Capital expenditures	(978,100,000)	(1,369,100,000)	(998,700,000)
Cash paid for purchase of businesses, net of cash acquired		(3,374,200,000)	(239,900,000)
Cash receipts on sold trade receivables			461,600,000
Investment in unconsolidated entities	(1,300,000)	(11,200,000)	(114,300,000)
Proceeds from sale of property, plant and equipment	34,900,000	119,100,000	23,300,000
Proceeds from property, plant and equipment insurance settlement	3,700,000	25,500,000	7,900,000
Intercompany notes issued		(75,700,000)
Intercompany notes proceeds		3,870,100,000
Other	1,700,000	100,000	27,600,000
Net cash used for investing activities	(939,100,000)	(815,400,000)	(832,500,000)
Financing activities:
Additions to revolving credit facilities	78,000,000	155,000,000	702,400,000
Repayments of revolving credit facilities	(178,200,000)	(160,000,000)	(572,200,000)
Additions to debt	696,400,000	959,800,000	852,500,000
Repayments of debt	(594,200,000)	(2,274,100,000)	(985,100,000)
Other financing (repayments) additions	(34,300,000)	6,200,000	(154,300,000)
Cash distributions paid to noncontrolling interests	(2,400,000)	(4,300,000)	(33,300,000)
Intercompany notes borrowing		100,000	1,400,000
Intercompany notes payments	(5,700,000)	(16,000,000)	(4,500,000)
Intercompany capital receipt		563,000,000	2,000,000
Intercompany capital distribution			(82,600,000)
Intercompany dividends			(28,400,000)
Other	(17,100,000)	36,000,000	31,600,000
Net cash (used for) provided by financing activities	(57,500,000)	(734,300,000)	(270,500,000)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(28,600,000)	4,000,000	(28,200,000)
Increase (decrease) in cash, cash equivalents and restricted cash	11,600,000	(12,000,000)	(114,900,000)
Cash, cash equivalents and restricted cash at beginning of period	133,800,000	145,800,000	260,700,000
Cash, cash equivalents and restricted cash at end of period	145,400,000	133,800,000	145,800,000
Eliminations [Member]
Operating activities:
Net cash provided by (used for) operating activities			(28,400,000)
Investing activities:
Intercompany notes issued		75,800,000	1,400,000
Intercompany notes proceeds	(5,700,000)	(3,886,100,000)	(4,500,000)
Intercompany capital investment		1,126,000,000	2,000,000
Intercompany return of capital			(82,600,000)
Net cash used for investing activities	(5,700,000)	(2,684,300,000)	(83,700,000)
Financing activities:
Intercompany notes borrowing		(75,800,000)	(1,400,000)
Intercompany notes payments	5,700,000	3,886,100,000	4,500,000
Intercompany capital receipt		(1,126,000,000)	(2,000,000)
Intercompany capital distribution			82,600,000
Intercompany dividends			28,400,000
Net cash (used for) provided by financing activities	$ 5,700,000	$ 2,684,300,000	$ 112,100,000

Selected Condensed Consolidat_6

Selected Condensed Consolidating Financial Statements of Parent, Issuer, Guarantors and Non-Guarantors - Noncash Operating, Investing and Financing Activities (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Parent [Member]
Operating activities:
Intercompany receivables		$ (140.9)
Investing activities:
Intercompany capital investment	$ (407.3)	(10,396.2)
Intercompany return of capital	442	606.7
Financing activities:
Intercompany capital distribution		(563)
Issuer [Member]
Investing activities:
Intercompany notes issued	(13.9)	(3,800)
Intercompany notes proceeds		4,519.8
Intercompany capital investment	(625.6)	(5,895.5)	$ (755.3)
Intercompany return of capital	35.6	1,479.6	1,356.3
Financing activities:
Intercompany notes borrowing	117	4,436.3
Intercompany notes payments			(69)
Intercompany capital receipt		10,396.2
Intercompany capital distribution	(442)	(606.7)
Guarantor Subsidiaries [Member]
Investing activities:
Intercompany notes issued	(70.4)	(4,667.2)
Intercompany notes proceeds	80.6	4,536.8
Intercompany capital investment	(990.2)	(6,889.3)	(335.3)
Intercompany return of capital	727	1,032.7	766
Financing activities:
Intercompany notes borrowing		2,541.5	392.1
Intercompany notes payments	(322.5)	(3,022)	(14)
Intercompany capital receipt	625.2	5,413.7	736.9
Intercompany capital distribution	(21.2)	(457.5)	(1,356.3)
Intercompany dividends paid	(48.3)	(302.2)
Non-Guarantor Subsidiaries [Member]
Operating activities:
Intercompany payables		140.9
Investing activities:
Intercompany notes issued	(117)	(10,777.8)	(392.1)
Intercompany notes proceeds	322.5	6,822	83
Financing activities:
Intercompany notes borrowing	84.3	12,267.2
Intercompany notes payments	(80.6)	(12,856.6)
Intercompany capital receipt	1,397.9	7,371.1	353.7
Intercompany capital distribution	(741.4)	(1,491.8)	(766)
Intercompany dividends paid	(1,287.3)	(1,435)	(285.9)
Eliminations [Member]
Operating activities:
Intercompany receivables		140.9
Intercompany payables		(140.9)
Investing activities:
Intercompany notes issued	201.3	19,245	392.1
Intercompany notes proceeds	(403.1)	(15,878.6)	(83)
Intercompany capital investment	2,023.1	23,181	1,090.6
Intercompany return of capital	(1,204.6)	(3,119)	(2,122.3)
Financing activities:
Intercompany notes borrowing	(201.3)	(19,245)	(392.1)
Intercompany notes payments	403.1	15,878.6	83
Intercompany capital receipt	(2,023.1)	(23,181)	(1,090.6)
Intercompany capital distribution	1,204.6	3,119	2,122.3
Intercompany dividends paid	$ 1,335.6	$ 1,737.2	$ 285.9

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2020	Oct. 01, 2019
Lessee Lease Description [Line Items]
ROU assets			$ 658.6
Operating lease liabilities			$ 718.5
Rental expense	$ 346.7	$ 243.7
ASC 842 [Member]
Lessee Lease Description [Line Items]
ROU assets				$ 731.1
Operating lease liabilities				$ 783.9

Leases - Schedule of Components

Leases - Schedule of Components of Lease Costs (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Lease Cost [Abstract]
Operating lease costs	$ 201.2
Variable and short-term lease costs	105.5
Sublease income	(6.7)
Finance lease cost:
Amortization of lease assets	10.5
Interest on lease liabilities	7.9
Total lease cost, net	$ 318.4

Leases - Summary of Supplementa

Leases - Summary of Supplemental Balance Sheet Information Related to Leases (Details) $ in Millions	Sep. 30, 2020USD ($)
Supplementary Information Balance Sheets [Abstract]
Operating lease right-of-use asset	$ 658.6
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseRightOfUseAsset
Current operating lease liabilities	$ 172.7
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiabilityCurrent
Noncurrent operating lease liabilities	$ 545.8
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiabilityNoncurrent
Total operating lease liabilities	$ 718.5
Property, plant and equipment	143.2
Accumulated depreciation	(19.1)
Property, plant and equipment, net	124.1
Current finance lease liabilities	$ 9
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:FinanceLeaseLiabilityCurrent
Noncurrent finance lease liabilities	$ 265.8
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:FinanceLeaseLiabilityNoncurrent
Total finance lease liabilities	$ 274.8

Leases - Summary of Lease Term

Leases - Summary of Lease Term and Discount Rate (Details)	Sep. 30, 2020
Weighted average remaining lease term:
Operating leases	5 years 10 months 24 days
Finance leases	9 years
Weighted average discount rate:
Operating leases	2.60%
Finance leases	4.00%

Leases - Summary of Supplemen_2

Leases - Summary of Supplemental Cash Flow Information Related to Leases (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows related to operating leases	$ 204.1
Operating cash flows related to finance leases	7.8
Financing cash flows related to finance leases	10.1
ROU assets obtained in exchange for lease liabilities:
Operating leases	$ 124.4

Leases - Summary of Maturity of

Leases - Summary of Maturity of Lease Liabilities (Details) $ in Millions	Sep. 30, 2020USD ($)
Maturity Of Lease Liabilities [Abstract]
Operating Leases, Fiscal 2021	$ 188.7
Operating Leases, Fiscal 2022	151.4
Operating Leases, Fiscal 2023	119.1
Operating Leases, Fiscal 2024	94.1
Operating Leases, Fiscal 2025	63.2
Operating Leases, Thereafter	164.4
Operating Leases, Total lease payments	780.9
Operating Leases, Less: Interest	(62.4)	[1]
Operating Leases, Present value of future lease payments	718.5
Finance Leases, Fiscal 2021	16.3
Finance Leases, Fiscal 2022	15.3
Finance Leases, Fiscal 2023	13.2
Finance Leases, Fiscal 2024	12
Finance Leases, Fiscal 2025	12
Finance Leases, Thereafter	288.3
Finance Leases, Total lease payments	357.1
Finance Leases, Less: Interest	(82.3)	[1]
Finance Leases, Present value of future lease payments	274.8
Fiscal 2021	205
Fiscal 2022	166.7
Fiscal 2023	132.3
Fiscal 2024	106.1
Fiscal 2025	75.2
Thereafter	452.7
Total lease payments	1,138
Less: Interest	(144.7)	[1]
Present value of future lease payments	$ 993.3
[1]

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments Under All Noncancelable Operating Leases (Details) $ in Millions	Sep. 30, 2019USD ($)
Leases [Abstract]
Fiscal 2020	$ 214.3
Fiscal 2021	180.1
Fiscal 2022	136.3
Fiscal 2023	108.3
Fiscal 2024	85.3
Thereafter	206.1
Total future minimum lease payments	$ 930.4

Special Purpose Entities (Detai

Special Purpose Entities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Dec. 06, 2013	Dec. 31, 2007
Debt Instrument [Line Items]
Restricted assets held by special purpose entities	$ 1,267.5	$ 1,274.3
Non-recourse liabilities held by special purpose entities	$ 1,136.5	$ 1,145.2
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	$ 372.4			$ 398
MeadWestvaco [Member] | Secured Financing Liability, Maturity in October 2027 [Member]
Debt Instrument [Line Items]
Non-recourse liabilities held by special purpose entities	326.2			$ 338.3
MeadWestvaco [Member] | Installment Note [Member]
Debt Instrument [Line Items]
Restricted assets held by special purpose entities	895.1		$ 860
MeadWestvaco [Member] | Secured Financing Liability, Maturity in December 2023 [Member]
Debt Instrument [Line Items]
Non-recourse liabilities held by special purpose entities	$ 810.3		$ 774

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Related Party Transaction [Line Items]
Net sales to affiliated companies	$ 311.5	$ 368.4	$ 418.8
Accounts receivable due from affiliated companies	$ 23.3	$ 23

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) T in Millions, R$ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)CountrylawsuitSubsidiaryT	Sep. 30, 2020BRL (R$)SubsidiaryT	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 5,700,000
Approximate tons of paper diverted | T	8	8
Number of countries | Country	170
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 6,600,000		$ 9,700,000	$ 5,800,000
Guarantor Obligations, Estimated Exposure, Undiscounted	50,000,000
Guarantor Obligations, Current Carrying Value	9,600,000
Indirect tax claim - receivable for expected recovery and interest	51,900,000		$ 12,200,000
Indirect tax claim - reduction of cost of goods sold	32,100,000
Indirect tax claim - reduction of interest expense, net	20,500,000
Brazil Administrative Council of Tax Appeals [Member]
Commitments and Contingencies [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 123,000,000	R$ 693
Tax claim and conversion description	The matter has proceeded through the Brazil Administrative Council of Tax Appeals (“CARF”) principally in two proceedings, covering tax years 2003 to 2008 and 2009 to 2012.	The matter has proceeded through the Brazil Administrative Council of Tax Appeals (“CARF”) principally in two proceedings, covering tax years 2003 to 2008 and 2009 to 2012.
Income tax settlement claim liability	$ 0
Tax claim and conversion, tax dispute related to tax years description	2003 to 2008	2003 to 2008
Tax claim and conversion, tax penalties relating to tax years description	2009 to 2012	2009 to 2012
Tax claim and conversion proceedings covering tax years description	2003 to 2008 and 2009 to 2012	2003 to 2008 and 2009 to 2012
Brazil [Member]
Commitments and Contingencies [Line Items]
Number of subsidiaries | Subsidiary	2	2
Asbestos Litigation [Member]
Commitments and Contingencies [Line Items]
Number of Lawsuits the Company Has Been Named a Defendant in Asbestos-related Personal Injury Litigation | lawsuit	1,200
Amount reserved for litigation	$ 15,200,000
Other Long Term Liabilities [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	3,000,000
Other Current Liabilities [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2,700,000
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment, Estimated Amount	$ 310,000,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss and Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]	$ (1,069.2)		$ (695.3)
Other comprehensive income (loss) before reclassifications	[1]	(219.5)		(392.3)
Amounts reclassified from accumulated other comprehensive (income) loss	[1]	42.2		18.4
Net current period other comprehensive income (loss)		(177.3)	[1]	(373.9)	[1]	$ (238)
Reclassification of stranded tax effects	[1]	(73.4)
Balance at end of period	[1]	(1,319.9)		(1,069.2)		(695.3)
Accumulated Net Gain (Loss) from Designated or Quality Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		0.7		(0.2)
Other comprehensive income (loss) before reclassifications		(9.9)		1.1
Amounts reclassified from accumulated other comprehensive (income) loss		3.6		(0.2)
Net current period other comprehensive income (loss)		(6.3)		0.9
Reclassification of stranded tax effects		0
Balance at end of period		(5.6)		0.7		(0.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(698)		(465.9)
Other comprehensive income (loss) before reclassifications		5.1		(250.7)
Amounts reclassified from accumulated other comprehensive (income) loss		38.6		18.6
Net current period other comprehensive income (loss)		43.7		(232.1)
Reclassification of stranded tax effects		(73.4)
Balance at end of period		(727.7)		(698)		(465.9)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(371.9)		(229.2)
Other comprehensive income (loss) before reclassifications		(214.7)		(142.7)
Amounts reclassified from accumulated other comprehensive (income) loss		0		0
Net current period other comprehensive income (loss)		(214.7)		(142.7)
Reclassification of stranded tax effects		0
Balance at end of period		$ (586.6)		$ (371.9)		$ (229.2)
[1]	All amounts are net of tax and noncontrolling interest.

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss and Other Comprehensive Loss - Summary of Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount		$ 48.3	$ 23.3	$ 20.9
Amortization of net actuarial loss, Tax		12.9	6.1	5.9
Amortization and settlement recognition of net actuarial loss, included in pension cost		35.4	17.2	15
Amortization of prior service credits (costs), Pre-Tax Amount		5.1	2.4	0.3
Amortization of prior service credits (costs), Tax		(1.3)	(0.6)	(0.1)
Amortization of prior service credits (costs), Net of Tax		3.8	1.8	0.2
Reclassification of stranded tax effects net	[1]	73.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax		4.9	(0.3)	0.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		1.3	(0.1)	0.2
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		3.6	(0.2)	$ 0.5
Parent [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net actuarial loss, Pre-Tax Amount	[2],[3]	(47.7)	(22.7)
Amortization of net actuarial loss, Tax	[2],[3]	12.8	5.9
Amortization and settlement recognition of net actuarial loss, included in pension cost	[2],[3]	(34.9)	(16.8)
Amortization of prior service credits (costs), Pre-Tax Amount	[2],[3]	(5)	(2.4)
Amortization of prior service credits (costs), Tax	[2],[3]	1.3	0.6
Amortization of prior service credits (costs), Net of Tax	[2],[3]	(3.7)	(1.8)
Defined Benefit Plans, before Tax	[2]	(52.7)	25.1
Defined Benefit Plans, Tax	[2]	87.5	6.5
Defined Benefit Plans, Net of Tax	[2]	34.8	18.6
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax		(4.9)	0.3
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		1.3	(0.1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		(3.6)	0.2
Total Reclassifications From Other Comprehensive Income Before Tax	[2]	(57.6)	(24.8)
Total Reclassifications From Other Comprehensive Income Tax Portion	[2]	88.8	6.4
Total Reclassifications From Other Comprehensive Income Net of Tax	[2]	31.2	(18.4)
Parent [Member] | Interest Rate 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],[4]	(2.3)	0.3
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[4]	0.6	(0.1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[4]	(1.7)	$ 0.2
Parent [Member] | Natural Gas Commodity Hedge [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]	(2.6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	[2],[5]	0.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[2],[5]	(1.9)
Parent [Member] | ASU 2018-02 [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification of stranded tax effects	[6]	73.4
Reclassification of stranded tax effects net	[6]	$ 73.4
[1]	All amounts are net of tax and noncontrolling interest.
[2]	Amounts in parentheses indicate charges to earnings. Amounts pertaining to noncontrolling interests are excluded.
[3]	These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See “ Note 5. Retirement Plans
[4]	These accumulated other comprehensive income components are included in Interest expense, net.
[5]	These accumulated other comprehensive income components are included in Cost of goods sold.
[6]	Amount reclassified to retained earnings as a result of the adoption of ASU 2018-02.

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Loss and Other Comprehensive Loss - Schedule of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018
Other Comprehensive Income Loss [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation (Loss) Gain, before Tax	$ (215)		$ (143.4)		$ (234.4)
Net deferred gain (loss) on cash flow hedges, Pre-Tax Amount	(13.3)		1.5
Reclassification adjustment of net (gain) loss on cash flow hedges included in earnings, Pre-Tax Amount	4.9		(0.3)		0.7
Net actuarial gain (loss) arising during period, Pre-Tax Amount	34.6		(335.9)		(29)
Amortization of net actuarial loss, Pre-Tax Amount	48.3		23.3		20.9
Prior service cost arising during the period, Pre-Tax Amount	(26.9)		(3.9)		(7.8)
Amortization of prior service cost (credits), Pre-Tax Amount	5.1		2.4		0.3
Unrealized gain on available for sale security, before tax					0.8
Reclassification adjustment of net gain on available for sale security included in earnings, Pre-Tax					(1.5)
Consolidated other comprehensive loss	(162.3)		(456.3)		(250)
Less: Other comprehensive (income) loss attributable to noncontrolling interests	0.3		1.5		0
Other comprehensive loss attributable to common stockholders	(162)		(454.8)		(250)
Foreign currency translation (loss) gain, Tax	0		0		0
Net deferred gain (loss) on cash flow hedges, Tax	3.3		(0.4)
Reclassification adjustment of net (gain) loss on cash flow hedges included in earnings, Tax	(1.3)		0.1		(0.2)
Net actuarial gain (loss) arising during period, Tax	(10.4)		87.4		15.9
Amortization of net actuarial loss, Tax	(12.9)		(6.1)		(5.9)
Other Comprehensive Income (Loss), Pension and Other Postretirement Plans, Net Prior Service Credit Arising During Period, Tax	7.3		0.6		2.3
Amortization of prior service cost (credit), Tax	(1.3)		(0.6)		(0.1)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax					0
Reclassification adjustment of net gain on available for sale security included in earnings, Tax					0
Consolidated other comprehensive loss	(15.3)		81		12
Less: Other comprehensive income (loss) attributable to noncontrolling interests, Tax	0		(0.1)		0
Other comprehensive loss attributable to common stockholders	(15.3)		80.9		12
Foreign currency translation (loss) gain, Net of Tax Amount	(215)		(143.4)		(234.4)
Deferred (loss) gain on cash flow hedges	(10)		1.1		0
Reclassification adjustment of net (gain) loss on cash flow hedges included in earnings, Net of Tax Amount	3.6		(0.2)		0.5
Net actuarial gain (loss) arising during period	24.2		(248.5)		(13.1)
Amortization and settlement recognition of net actuarial loss, included in pension and postretirement cost	35.4		17.2		15
Prior service cost arising during period	(19.6)		(3.3)		(5.5)
Amortization and curtailment recognition of prior service (credit) cost, included in pension and postretirement cost	3.8		1.8		0.2
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax					0.8
Reclassification adjustment of net gain on available for sale security included in earnings, Net of Tax	0		0		(1.5)
Other comprehensive (loss) income, net of tax	(177.6)		(375.3)		(238)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0.3		1.4		0
Net current period other comprehensive income (loss)	(177.3)	[1]	(373.9)	[1]	(238)
Net deferred gain on cash flow hedges, Net of Tax Amount	(10)		1.1		0
Net actuarial loss arising during period, Net of Tax Amount	$ 24.2		$ (248.5)		$ (13.1)
[1]	All amounts are net of tax and noncontrolling interest.

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Jul. 31, 2015
Equity [Abstract]
Stock repurchase program, number of shares authorized to be repurchased				40,000,000
Authorized share repurchase as a percentage of common stock outstanding				15.00%
Treasury stock, shares, acquired	0	2,100,000	3,400,000
Purchases of common stock	$ 0	$ 88,600,000	$ 195,100,000
Stock repurchase program, remaining number of shares authorized to be repurchased	19,100,000

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) - USD ($)	Nov. 02, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Feb. 02, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 130,300,000	$ 64,200,000	$ 66,800,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		33,200,000	16,300,000	19,400,000
Proceeds from Stock Options Exercised		$ 32,400,000	$ 61,500,000	$ 44,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Stock options granted during period		0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Stock Appreciation Rights, Exercises in Period, Intrinsic Value		$ 200,000	$ 0	$ 500,000
KapStone [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ratio of KapStone Shares to WestRock Shares	0.83%
Fair value of share-based awards issued in business combinations	$ 70,800,000
Granted	2,665,462
Weighted average grant date fair value, granted	$ 20.99
Amended and Restated 2016 Incentive Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for Issuance					11,700,000
Number of shares available for grant		1,200,000
Prior Plans Assumed in Mergers and Acquisitions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant		18,100,000
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
Aggregate intrinsic value of options exercised		$ 11,800,000	$ 44,500,000	$ 67,400,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition		2 months 12 days
Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized		$ 100,000

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Details) - Stock Options [Member] - KapStone [Member]	Nov. 02, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term in years	3 years 1 month 6 days
Expected volatility	27.70%
Risk-free interest rate	3.00%
Dividend yield	4.10%

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Changes in Stock Options (Details) - Stock Options [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding | shares	4,396,177
Exercised | shares	(840,433)
Expired | shares	(93,691)
Forfeited | shares	(5,756)
Outstanding | shares	3,456,297
Exercisable at September 30, 2020 | shares	3,455,580
Vested and expected to vest at September 30, 2020 | shares	3,456,297
Weighted Average Exercise Price, Outstanding | $ / shares	$ 33.32
Weighted Average Exercise Price, Exercised | $ / shares	24.84
Weighted Average Exercise Price, Expired | $ / shares	38.21
Weighted Average Exercise Price, Forfeited | $ / shares	26.59
Weighted Average Exercise Price, outstanding, end of period | $ / shares	35.26
Weighted Average Exercise Price, exercisable at end of period | $ / shares	35.27
Weighted Average Exercise Price, Vested and expected to vest at September 30, 2020 | $ / shares	$ 35.26
Weighted Average Remaining Contractual Term (in years), Outstanding	3 years
Weighted Average Remaining Contractual Term (in years), Exercisable at September 30, 2020	3 years
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest at September 30, 2020	3 years
Aggregate Intrinsic Value, Outstanding | $	$ 12.9
Aggregate Intrinsic Value, Exercisable at September 30, 2020 | $	12.9
Aggregate Intrinsic Value,, Vested and expected to vest at September 30, 2020 | $	$ 12.9

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Changes in SARs (Details) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding | shares	34,972
Exercised | shares	(15,343)
Expired | shares	(2,647)
Outstanding | shares	16,982
Exercisable at September 30, 2020 | shares	16,982
Weighted Average Exercise Price, Outstanding | $ / shares	$ 28.41
Weighted Average Exercise Price, Exercised | $ / shares	27
Weighted Average Exercise Price, Expired | $ / shares	23.65
Weighted Average Exercise Price, outstanding, end of period | $ / shares	30.42
Weighted Average Exercise Price, Vested and expected to vest at September 30, 2020 | $ / shares	$ 30.42
Weighted Average Remaining Contractual Term (in years), Outstanding	1 year 1 month 6 days
Weighted Average Remaining Contractual Term (in years), Exercisable at September 30, 2020	1 year 1 month 6 days
Aggregate Intrinsic Value, Outstanding | $	$ 0.1
Aggregate Intrinsic Value, Exercisable at September 30, 2020 | $	$ 0.1

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
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%
Percentage of Award Based on Level of Performance Attained, Minimum		0.00%
Restricted Stock, Target Awards [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of awards vested	105.00%
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		$ 81.6
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition		1 year
Restricted Stock, Total Shareholder Return Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		3 years	2 years 10 months 24 days	2 years 10 months 24 days
Expected volatility		27.50%	27.20%	29.70%
Risk-free rate		1.30%	2.40%	2.30%
Stock Options [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 45.14	$ 42.64	$ 66.28
Restricted Stock, Target Awards, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved		98.80%
Restricted Stock, Target Awards, 2016 [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, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved				103.70%

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Changes in Unvested Restricted Stock (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Sep. 30, 2020		Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units, Unvested	3,645,538
Shares/Units, Granted	4,446,175		3,673,445	1,116,111
Shares/Units, Vested	(766,431)		(2,933,556)	(697,717)
Shares/Units, Forfeited	(709,915)
Shares/Units, Unvested	6,615,367		3,645,538
Weighted Average Grant Date Fair Value, Unvested	$ 51.94
Weighted Average Grant Date Fair Value, Granted	31.53
Weighted Average Grant Date Fair Value, Vested	51.39
Weighted Average Grant Date Fair Value, Forfeited	51.27
Weighted Average Grant Date Fair Value, Unvested	$ 38.36	[1]	$ 51.94
[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 aggregate outstanding grants to be attained at levels less than target. However, it is possible that the performance attained may vary.

Share-Based Compensation - Su_4

Share-Based Compensation - Summary of Changes in Unvested Restricted Stock (Parenthetical) (Details)	12 Months Ended
	Sep. 30, 2020
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%
Percentage of Award Based on Level of Performance Attained, Minimum	0.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Performance Based Awards Reflected	100.00%

Share-Based Compensation - Su_5

Share-Based Compensation - Summary of Restricted Stock Shares Granted (Details) - shares		Nov. 02, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
KapStone [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		2,665,462
Restricted Stock, Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[1]		49,236	39,792	23,285
Restricted Stock, Attainment of Performance Condition in Excess of Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[2]			1,149,592	45,964
Restricted Stock Service Condition and Cash Flow per Share Performance Condition at Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[3]		869,065	652,465	432,655
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	[3]		152,595	407,300	259,695
Restricted Stock with Service Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[4]		889,030	682,264	354,512
Restricted Stock For Annual Bonus [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			2,486,249
Restricted Stock with Service Condition Assumed in Purchase Accounting [Member] | KapStone [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[5]	742,032
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			4,446,175	3,673,445	1,116,111
[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 2020 for the fiscal 2017 Cash Flow Per Share were at 98.8% of target, therefore, the remainder of the grant was forfeited. Shares issued in fiscal 2019 for the fiscal 2016 Cash Flow Per Share were at 200% of target. Shares issued in fiscal 2018 for the fiscal 2015 Cash Flow Per Share were at 103.7% of target.
[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]	These shares vest over approximately three to four years.
[5]	These shares vest over approximately one to three years.

Share-Based Compensation - Su_6

Share-Based Compensation - Summary of Restricted Stock Shares Granted (Parenthetical) (Details)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
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, Target Awards, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Awarded Based on Performance Level Achieved	98.80%
Restricted Stock, Target Awards, 2016 [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, 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 [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%
Percentage of Award Based on Level of Performance Attained, Minimum	0.00%
Restricted Stock with Service Condition [Member] | Minimum [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
Restricted Stock with Service Condition [Member] | Maximum [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
Restricted Stock with Service Condition Assumed in Purchase Accounting [Member] | Minimum [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 with Service Condition Assumed in Purchase Accounting [Member] | Maximum [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_7

Share-Based Compensation - Summary of Restricted Stock Awards - Vested, Granted and Changes (Details) - Restricted Stock [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of restricted stock vested	766,431	2,933,556	697,717
Aggregate fair value of restricted stock vested	$ 29.6	$ 115.2	$ 46.1

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, 2020	Sep. 30, 2019	Sep. 30, 2018	Feb. 02, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 130.3	$ 64.2	$ 66.8
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	0.4	0.4	0.2
Share-based compensation expense	$ 2.1	$ 1.2	$ 1.6
Shares Available For Future Grant	1.6			2.5

Earnings per Share - Schedule o

Earnings per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net (loss) income attributable to common stockholders	$ (1,156)	$ 178.5	$ 148.1	$ 138.5	$ 310.8	$ 252.6	$ 160.4	$ 139.1	$ (690.9)	$ 862.9	$ 1,906.1
Less: Distributed and undistributed income available to participating securities, Basic									(0.1)	(0.1)	(0.2)
Distributed and undistributed (loss) income available to common stockholders, Basic									(691)	862.8	1,905.9
Less: Distributed and undistributed income available to participating securities, Diluted									(0.1)	(0.1)	(0.2)
Distributed and undistributed (loss) income available to common stockholders, Diluted									$ (691)	$ 862.8	$ 1,905.9
Basic weighted average shares outstanding									259.2	256.6	255.5
Effect of dilutive stock options and non-participating securities										2.5	4.3
Diluted weighted average shares outstanding									259.2	259.1	259.8
Basic (loss) earnings per share attributable to common stockholders	$ (4.45)	$ 0.69	$ 0.57	$ 0.54	$ 1.21	$ 0.98	$ 0.63	$ 0.55	$ (2.67)	$ 3.36	$ 7.46
Diluted (loss) earnings per share attributable to common stockholders	$ (4.45)	$ 0.69	$ 0.57	$ 0.53	$ 1.20	$ 0.98	$ 0.62	$ 0.54	$ (2.67)	$ 3.33	$ 7.34

Earnings per Share - Additional

Earnings per Share - Additional Information (Details) - shares shares in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4.2	1.3	0.2

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, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Data [Abstract]
Net sales	$ 4,471.5	$ 4,236.3	$ 4,447.3	$ 4,423.7	$ 4,651.6	$ 4,690	$ 4,620	$ 4,327.4	$ 17,578.8	$ 18,289	$ 16,285.1
Gross profit	813.4	770	804.8	809	1,078.7	988.9	899.6	781.8	3,197.2	3,749	3,362
(Gain) loss on disposal of assets	(10.4)	1	(5.6)	(1.3)	(3.9)	6.5		(43.8)	(16.3)	(41.2)	10.1
Multiemployer pension withdrawal (income) expense		(2)	0.9		(4.6)	(1.7)			(1.1)	(6.3)	184.2
Land and Development impairments							13			13	31.9
Restructuring and other costs	56.5	9.7	16.4	30.1	66.6	17.9	34.8	54.4	112.7	173.7	105.4
Goodwill impairment	1,333.2								1,333.2
(Loss) gain on extinguishment of debt	(0.4)	(0.6)	(0.5)		(0.4)	(3.2)	0.4	(1.9)	(1.5)	(5.1)	(0.1)
Income tax (expense) benefit	(40)	(19.2)	(57.8)	(46.5)	(89.3)	(77.6)	(47.2)	(62.7)	(163.5)	(276.8)	874.5
Consolidated net income (loss)	(1,154.5)	180	148.9	139.5	312.4	253.8	161.9	139.8	(686.1)	867.9	1,909.3
Net income (loss) attributable to common stockholders	$ (1,156)	$ 178.5	$ 148.1	$ 138.5	$ 310.8	$ 252.6	$ 160.4	$ 139.1	$ (690.9)	$ 862.9	$ 1,906.1
Basic earnings (loss) per share attributable to common stockholders	$ (4.45)	$ 0.69	$ 0.57	$ 0.54	$ 1.21	$ 0.98	$ 0.63	$ 0.55	$ (2.67)	$ 3.36	$ 7.46
Diluted earnings (loss) per share attributable to common stockholders	$ (4.45)	$ 0.69	$ 0.57	$ 0.53	$ 1.20	$ 0.98	$ 0.62	$ 0.54	$ (2.67)	$ 3.33	$ 7.34

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, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2020
Quarterly Financial Data [Line Items]
Basic Earnings Per Share, Estimated Increase (Decrease) Due to Specific Items Occurring During Quarter		$ (0.09)	$ 0.18	$ 0.19	$ (0.14)
Diluted Earnings Per Share, Estimated Increase (Decrease) Due to Specific Items Occurring During Quarter		$ (0.09)	$ 0.17	$ 0.18	$ (0.14)
Goodwill impairment	$ 1,333.2					$ 1,333.2
Goodwill impairment, after tax						$ 1,314.3
Atlanta Beverage Facility [Member]
Quarterly Financial Data [Line Items]
Pre-tax gain on sale of business					$ 48.5
KapStone [Member]
Quarterly Financial Data [Line Items]
Pre-tax expense for inventory stepped-up in purchase accounting					24.7
Hurricane Michael [Member]
Quarterly Financial Data [Line Items]
Unusual or infrequent item, net income (increase) decrease pretax				$ (63.4)
Pre-tax of direct expenses				6.6	39.8
Insurance proceeds received				$ 70	20
Estimated pre-tax lost of production and sales					$ 31.4
Goodwill Impairment [Member]
Quarterly Financial Data [Line Items]
Goodwill impairment	1,333.2
Goodwill impairment, after tax	$ 1,314.3
Basic loss per share due to goodwill impairment	$ (5.06)
Diluted loss per share due to goodwill impairment	$ (5.06)
Expected Recovery and Interest Related to Indirect Tax Claim [Member]
Quarterly Financial Data [Line Items]
Unusual or infrequent item, net income (increase) decrease pretax			$ (33.8)
Hurricane Michael Insurance Proceeds Received [Member]
Quarterly Financial Data [Line Items]
Unusual or infrequent item, net income (increase) decrease pretax			$ (29.5)
One-time COVID-19 Recognition Awards [Member]
Quarterly Financial Data [Line Items]
Unusual or infrequent item, net income (increase) decrease pretax		$ 31.6