Goodwill and Intangible Assets - Details (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 35.1
Net proceeds from divested assets			$ 70.9
Goodwill, Impairment Loss	0.0	$ 0.0	(195.1)
Goodwill and intangible assets, net	48.8	52.0	59.2
Amortization of Intangible Assets	(3.2)	(7.2)
Finite-Lived Intangible Assets, Accumulated Amortization	$ 50.1	46.9	39.7
Minimum [Member]
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum [Member]
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Consumer Products [Member]
Goodwill [Line Items]
Goodwill, Written off Related to Sale of Business Unit			(14.0)
Intangible Assets, Net (Excluding Goodwill)	$ 0.0	0.3	4.6
Amortization of Intangible Assets	(0.3)	(4.3)
Pulp And Paperboard [Member]
Goodwill [Line Items]
Goodwill	35.1	35.1	35.1
Intangible Assets, Net (Excluding Goodwill)	13.7	16.6	$ 19.5
Amortization of Intangible Assets	(2.9)	(2.9)
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Net (Excluding Goodwill)	12.8	15.0
Trademarks and Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Net (Excluding Goodwill)	0.7	1.7
Other Intangible Assets [Member]
Goodwill [Line Items]
Intangible Assets, Net (Excluding Goodwill)	$ 0.2	$ 0.2

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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