General Information - Business Combinations and Shutdown and Other Special Charges, Net (Details) $ in Millions			3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 01, 2020 facility	Aug. 01, 2019 facility mill	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) mill	Jun. 30, 2019 USD ($)	Dec. 31, 2022 USD ($) mill	Dec. 31, 2019
Business Acquisition [Line Items]
Charges Associated with Business Combinations			$ (5.5)	$ 0.5	$ (4.0)	$ 2.6
Shutdown and Other Special Charges			22.0	9.4	26.2	13.5
Exit Activities			4.0	0.0	17.0	0.0
Total			20.5	$ 9.9	$ 39.2	$ 16.1
Number of converting facilities | facility	7
Increase in multi-employer plan withdrawal obligation			12.2
Number of mills to be closed | mill					2
Number of facilities acquired | facility		2
Length of program to dismantle and dispose of abandoned assets								3 years
Artistic Carton Company
Business Acquisition [Line Items]
Number of mills acquired | mill		1
Quad/Graphics, Inc.
Business Acquisition [Line Items]
Bargain purchase gain			6.6
Paperboard Mills
Business Acquisition [Line Items]
Expected costs associated with closures			$ 40.0		$ 40.0
Forecast | Facility Closing
Business Acquisition [Line Items]
Number of mills to be closed | mill							2
Forecast | Construction in Progress
Business Acquisition [Line Items]
Investment in new CRB Mill							$ 600.0