Summary of Significant Accounting Policies, Narrative, Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment
Interest expense capitalized as construction in progress	$ 1.6	$ 1.7	$ 2.2
Depreciation expense	46.3	42.1	38.3
Non-cash asset impairment charges	26.1	1.4	19.2
Fabricated Products | Idled equipment
Property, Plant and Equipment
Non-cash asset impairment charges	$ 0.9	$ 1.4	$ 0.8
Minimum | Land improvements
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	3 years
Minimum | Buildings and leasehold improvements
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	5 years
Minimum | Machinery and equipment
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	1 year
Minimum | Finance lease assets
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	2 years
Maximum | Land improvements
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	25 years
Maximum | Buildings and leasehold improvements
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	45 years
Maximum | Machinery and equipment
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	22 years
Maximum | Finance lease assets
Property, Plant and Equipment
Property, plant and equipment useful lives (in years)	15 years