Derivative Instruments and Hedging Activities (Details) € in Millions, $ in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) MMBTU MW t lb	Jun. 30, 2018 CAD ($) MMBTU MW t lb	Jun. 30, 2018 EUR (€) MMBTU MW t lb	Dec. 31, 2017 CAD ($) MMBTU MW t lb	Dec. 31, 2017 EUR (€) MMBTU MW t lb
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 0.0
Commodity Contract [Member] | Nickel [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Derivatives | lb	300,000	300,000	300,000	500,000	500,000
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Aug. 31, 2018
Commodity Contract [Member] | Natural Gas [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Derivatives | MMBTU	39,868,000	39,868,000	39,868,000	41,338,000	41,338,000
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Jun. 30, 2020
Gains (losses) expected to be reclassified into cost of products sold within the next twelve months	$ 0.7
Commodity Contract [Member] | Zinc [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Derivatives | lb	46,150,000	46,150,000	46,150,000	50,350,000	50,350,000
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Jun. 30, 2020
Gains (losses) expected to be reclassified into cost of products sold within the next twelve months	$ (2.1)
Commodity Contract [Member] | Iron Ore [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Derivatives | t	2,210,000	2,210,000	2,210,000	2,340,000	2,340,000
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	May 31, 2020
Commodity Contract [Member] | Electricity [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Derivatives | MW	1,676,000	1,676,000	1,676,000	1,553,000	1,553,000
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Jun. 20, 2020
Gains (losses) expected to be reclassified into cost of products sold within the next twelve months	$ 2.5
Foreign Exchange Contract [Member] | Euro Member Countries, Euro
Derivative [Line Items]
Derivative, Notional Amount | €			€ 9.0		€ 26.0
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Dec. 31, 2018
Foreign Exchange Contract [Member] | Canada, Dollars
Derivative [Line Items]
Derivative, Notional Amount		$ 147.7		$ 148.1
Beginning Settlement Date	Jul. 01, 2018
Ending Settlement Date	Dec. 31, 2021
Gains (losses) expected to be reclassified into cost of products sold within the next twelve months	$ (0.9)