Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 16.1	$ 16.1	$ 9.7
Goodwill, Additions during period	0.0	6.4
Acquired Intangible Assets, including Goodwill	0.0	17.4
Amortization of Intangible Assets	(3.7)	(3.6)
Intangible Assets, Net (Including Goodwill)	66.9	70.6	56.8
Payments to Acquire Businesses, Gross	22.0
Future Amortization Expense, Year One	3.8
Future Amortization Expense, Year Two	3.8
Future Amortization Expense, Year Three	3.8
Future Amortization Expense, Year Four	3.8
Future Amortization Expense, Year Five	3.8
Timber licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	40.7	43.9	47.1
Amortization of Intangible Assets	(3.2)	(3.2)
Timber Licenses, Initial Value	91.3
Technology-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	10.1	10.6	$ 0.0
Finite-lived Intangible Assets Additions during period	0.0	11.0
Amortization of Intangible Assets	$ 0.5	$ 0.4