Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Amortizable Portion

+ References

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- Definition

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Lives of Underlying Assets

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- Definition

Pre-Tax Inventory Step-Up

+ References

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Segment Information - Additional Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	3
Pre-Tax Inventory Step-Up	$ 1.0	$ 26.5	$ 8.1
Corrugated Packaging [Member]
Segment Reporting Information [Line Items]
Pre-Tax Inventory Step-Up	1.0	1.4	3.4
Corrugated Packaging [Member] \| Grupo Gondi Investment [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	133.9	76.2
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Amortizable Portion	$ 62.1	59.2
Corrugated Packaging [Member] \| Grupo Gondi Investment [Member] \| Minimum [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Lives of Underlying Assets	10 years
Corrugated Packaging [Member] \| Grupo Gondi Investment [Member] \| Maximum [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Lives of Underlying Assets	15 years
Consumer Packaging [Member]
Segment Reporting Information [Line Items]
Pre-Tax Inventory Step-Up		$ 25.1	$ 4.7