Exit Activities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) employee	Mar. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of mills to be closed | employee	2
Exit activities charges incurred	$ 13.0	$ 0.0
One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Recorded exit costs to date	17.6
One-time Termination Benefits | Minimum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	15.0
One-time Termination Benefits | Minimum | White Pigeon and West Monroe
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	4.0
One-time Termination Benefits | Maximum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Expected costs associated with closures	20.0
Facility Closing | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	11.8
Exit activities charges incurred	9.3
Facility Closing | White Pigeon and West Monroe
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	8.5
Exit activities charges incurred	2.9
Facility Closing | Minimum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	50.0
Facility Closing | Minimum | White Pigeon and West Monroe
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	13.0
Facility Closing | Maximum | Two CRB Mills
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	60.0
Facility Closing | Maximum | White Pigeon and West Monroe
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation related to plant closure	$ 18.0