Other Expense, Net - Components of Other Expense, Net (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset disposals and write-offs		$ (14.7)	$ (6.0)
Facilities closure and other costs	[1]	(2.1)	(0.4)
Other		(3.1)	(3.6)
Total		(20.4)	$ (10.0)
Jackson, Alabama Mill
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Conversion	[2]	$ (0.5)

[1] Includes charges consisting of closure costs related to corrugated products facilities.

[2] Includes charges related to the announced discontinuation of production of uncoated freesheet paper grades on the No. 3 machine at the Jackson, Alabama mill in the first quarter of 2021 associated with the permanent conversion of the machine to produce linerboard.