High performance of virgin kraft linerboard machine percentage.

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

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The amount of insurance-related assessment liability that is expected to be recovered through policy surcharges applied to in-force policies.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Segment Information - Selected Financial Information by Reportable Segment (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Charges for disposal of fixed assets				$ (6.7)	$ (4.9)
Wallula, Washington Mill
Segment Reporting Information [Line Items]
High-performance of virgin kraft linerboard machine percentage			100.00%
DeRidder, Louisiana Mill
Segment Reporting Information [Line Items]
Charges for disposal of fixed assets	$ 3.0			3.0
Paper \| Wallula, Washington Mill
Segment Reporting Information [Line Items]
Restructuring charges		$ 4.0		$ 0.6	26.4
High-performance of virgin kraft linerboard machine percentage		100.00%		100.00%
Packaging And Corporate And Other
Segment Reporting Information [Line Items]
Restructuring charges		$ 1.3			1.8
Packaging
Segment Reporting Information [Line Items]
Property damage and business interruption insurance		0.5			0.5
Acquisition-related costs		$ 0.1			$ 0.1