Other Operating Charges, net (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Gain on divested assets	$ 0.0		$ (1.4)	$ 0.0			$ (1.4)	$ 0.0
Other operating charges, net	0.3	$ (3.0)	(8.5)	1.9			11.9	2.1
Net income	21.4	22.8	10.3	(11.0)	$ (0.4)	$ 3.8	54.5	(7.6)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax	(1.8)			(1.3)			(5.5)	(3.9)
Other Comprehensive Income (Loss), Net of Tax	1.8			1.3			5.5	3.9
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	23.2			(9.7)			60.0	(3.7)
Director [Member]
Share based compensation expense	0.3	1.9	0.2	0.4			2.5	0.1
Reorganization Expenses [Member]
Other Cost and Expense, Operating	0.0	$ 0.6	2.8	0.9			3.4	1.0
Union settlement [Member]
Other Cost and Expense, Operating	0.0		6.6	0.0			6.6	0.0
Other Expense [Member]
Other Cost and Expense, Operating	$ 0.0			$ 0.6			$ 0.8	$ 1.0
Consumer Products | Union settlement [Member]
Other Cost and Expense, Operating			2.6
Pulp And Paperboard [Member] | Union settlement [Member]
Other Cost and Expense, Operating			$ 4.0