Property, Plant, and Equipment - Components of property, plant, and equipment (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost		$ 1,406.2	$ 1,328.7
Less: accumulated depreciation and depletion		(590.0)	(525.7)
Property, plant, and equipment, net		816.2	803.0
Productive Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost		211.0	201.9
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	[1]	331.4	316.5
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost		280.5	267.5
Machinery and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost		755.7	715.9
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost		$ 38.6	$ 28.8

[1] Includes depletable land of $211.0 million as of December 31, 2019 and $201.9 million as of December 31, 2018.