Derivative Financial Instruments and Related Hedging Programs, Narrative (Details) mmlbs in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) mmlbs	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016 EUR (€) mmlbs	Mar. 31, 2010 USD ($)
Derivative [Line Items]
Non-cash impairment charge	10 months
Derivative Instruments in Hedges, at Fair Value, Net	$ 4,000,000	$ (14,600,000)
Derivative Asset	5,800,000	1,600,000
Margin deposits with counterparties	0
Customer Deposits, Current	0
Aggregate fair value of derivative instruments that contain credit-risk-related contingency features that were in a net liability position	100,000	14,600,000
Convertible Notes | Convertible Notes Payable
Derivative [Line Items]
Principal amount of notes								$ 175,000,000
Foreign Exchange Contract | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	0	(300,000)	$ 0
Foreign Exchange Contract | Designated as Hedging Instrument | Purchase
Derivative [Line Items]
Derivative, Notional Amount	$ 2,200,000						€ 1,593,700
Derivative, Average Forward Exchange Rate	1.08						1.08
Alloy Metal Hedge | Designated as Hedging Instrument
Derivative [Line Items]
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	$ 0
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (100,000)	0	0
Alloy Metal Hedge | Designated as Hedging Instrument | Purchase
Derivative [Line Items]
Derivative notional amount | mmlbs	4.0						4.0
Minimum | Foreign Exchange Contract | Designated as Hedging Instrument | Purchase
Derivative [Line Items]
Derivative, Remaining Maturity	1 month
Maximum | Foreign Exchange Contract | Designated as Hedging Instrument | Purchase
Derivative [Line Items]
Derivative, Remaining Maturity	8 months
Maximum | Alloy Metal Hedge | Designated as Hedging Instrument | Purchase
Derivative [Line Items]
Derivative, Remaining Maturity	12 months
Scenario, Forecast | Natural Gas Member
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage				49.00%	72.00%	73.00%
Scenario, Forecast | Electricity Member
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage				36.00%	54.00%	54.00%
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Foreign Exchange Contract
Derivative [Line Items]
OCI, before Reclassifications, before Tax, Attributable to Parent	$ 0	(300,000)	0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Alloy Metal Hedge
Derivative [Line Items]
OCI, before Reclassifications, before Tax, Attributable to Parent	$ (100,000)	$ 0	$ 0