Derivative Financial Instruments and Hedging (Details) In Millions, unless otherwise specified	3 Months Ended																																					3 Months Ended			3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 31, 2015 Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2014 Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2015 Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2014 Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2015 Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2014 Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2015 Nickel and other raw material contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2014 Nickel and other raw material contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2015 Nickel and other raw material contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2014 Nickel and other raw material contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2015 Nickel and other raw material contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2014 Nickel and other raw material contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2015 Natural gas contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2014 Natural gas contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2015 Natural gas contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2014 Natural gas contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2015 Natural gas contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2014 Natural gas contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2015 Electricity contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2014 Electricity contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2015 Electricity contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2014 Electricity contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2015 Electricity contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2014 Electricity contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2015 Foreign exchange contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2014 Foreign exchange contracts Other Comprehensive Income Cash Flow Hedging USD ($)	Mar. 31, 2015 Foreign exchange contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2014 Foreign exchange contracts Cost Of Sales Cash Flow Hedging USD ($)	Mar. 31, 2015 Foreign exchange contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2014 Foreign exchange contracts Selling And Administrative Expenses Cash Flow Hedging USD ($)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Cash Flow Hedging USD ($)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Cash Flow Hedging EUR (€)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Cost Of Sales Fair Value Hedging USD ($)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Maturity dates Through February 2018 EUR (€)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Maturity Dates Through 2015 EUR (€)	Mar. 31, 2015 Designated as Hedging Instrument Foreign exchange forward Maturity Dates Through 2015 Fair Value Hedging EUR (€)	Mar. 31, 2015 Not Designated as Hedging Instrument Foreign exchange forward USD ($)	Mar. 31, 2015 Not Designated as Hedging Instrument Foreign exchange forward EUR (€)	Mar. 31, 2015 Not Designated as Hedging Instrument Foreign exchange forward Maturity Dates Through February 2016 EUR (€)	Mar. 31, 2015 Not Designated as Hedging Instrument Foreign exchange contracts Cost Of Sales USD ($)	Mar. 31, 2014 Not Designated as Hedging Instrument Foreign exchange contracts Cost Of Sales USD ($)
Notional Disclosures [Abstract]
Percentage of estimated annual nickel requirements	20.00%
Percentage of forecasted natural gas usage hedged for 2015	80.00%
Percentage Of Forecasted Natural Gas Usage Hedged for 2016	75.00%
Percentage Of Forecasted Natural Gas Usage Hedged for 2017	45.00%
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative																																			€ 375	€ 157	€ 115			€ 30
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net		11.4	5.7					(9.6)	3.0					(6.0)	2.3					0	0.9					27.0	(0.5)
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net				1.7	(1.3)					(2.2)	(1.7)					(2.4)	1.4					(0.1)	0.4					6.4	(1.4)
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net						0	0					0	0					0	0					0	0					0	0
Derivative Instruments Gain Loss Recognized In Income Net																																									3.5	0.2
Notional amount of derivatives net settled																																	126.5						40.3
Cash proceeds from settlement of hedge																																26.1						11.8
Gain on derivative																																		5.0
Reclassification of Cash Flow Hedge Gain (Loss) [Abstract]
Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months	$ 0.7