Exit Activities (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) mill	Sep. 30, 2019 USD ($)	Dec. 31, 2022 USD ($) mill
Restructuring Cost and Reserve [Line Items]
Number of mills to be closed | mill			2
Exit activities charges incurred	$ 4.4	$ 3.0	$ 21.4	$ 3.0
Construction in Progress | Forecast
Restructuring Cost and Reserve [Line Items]
Investment in new CRB Mill					$ 600.0
One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Recorded exit costs to date	42.1		42.1
One-time Termination Benefits | Burlington, North Carolina Facility
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	1.4		1.4
One-time Termination Benefits | Minimum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	15.0		15.0
One-time Termination Benefits | Maximum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	$ 20.0		20.0
Facility Closing | Forecast
Restructuring Cost and Reserve [Line Items]
Number of mills to be closed | mill					2
Facility Closing | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure			21.6
Exit activities charges incurred			11.4
Facility Closing | White Pigeon and West Monroe
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure			15.8
Exit activities charges incurred			2.3
Facility Closing | Minimum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure			50.0
Facility Closing | Minimum | Burlington, North Carolina Facility
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure			3.6
Facility Closing | Maximum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure			$ 60.0