Income Taxes Reconciliation of deferred taxes (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance [Line Items]
Accrued liabilities	$ 21.4	$ 26.6
Pension and post-retirement benefits	8.3	19.9
Share-based compensation	5.3	6.9
Benefit of capital loss and NOL carryovers	15.8	38.9
Other	13.1	10.2
Inventory	7.7	6.6
Market value write down of ARS	3.3	4.9
Benefit of tax credit carryovers	0.4	3.5
Valuation Allowance, Amount	(12.0)	(13.6)
Deferred Tax Assets, Net	63.3	103.9
Property, plant and equipment	(111.8)	(118.2)
Timber and timberlands	9.8	11.4
Installment sale gain deferral	0.0	5.2
Total Deferred Tax Liabilities	(121.6)	(134.8)
Deferred Tax Liabilities, Net	(58.3)	(30.9)
Long-term deferred tax asset	(3.9)	(2.5)
Long-term deferred tax liability	$ (62.2)	$ (33.4)