Derivative Financial Instruments and Hedging (Details) € in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2015 EUR (€)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 EUR (€)
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					80.00%
Percentage Of Forecasted Natural Gas Usage Hedged for 2017					50.00%
Reclassification of Cash Flow Hedge Gain (Loss) [Abstract]
Cash Flow Hedge Gain Loss To Be Reclassified Within Twelve Months					$ 2.2
Other Comprehensive Income | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net	$ (6.4)			$ 7.9	5.0	$ 13.6
Cost Of Sales | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	1.3			0.3	3.0	(1.0)
Selling And Administrative Expenses | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net	0.0			0.0	0.0	0.0
Nickel and other raw material contracts | Other Comprehensive Income | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net	(3.5)			7.1	(13.1)	10.1
Nickel and other raw material contracts | Cost Of Sales | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	(2.4)			0.9	(4.6)	(0.8)
Nickel and other raw material contracts | Selling And Administrative Expenses | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net	0.0			0.0	0.0	0.0
Natural gas contracts | Other Comprehensive Income | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net	0.2			(1.0)	(5.8)	1.3
Natural gas contracts | Cost Of Sales | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	(2.4)			1.0	(4.8)	2.4
Natural gas contracts | Selling And Administrative Expenses | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net	0.0			0.0	0.0	0.0
Electricity contracts | Other Comprehensive Income | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net	0.0			(0.1)	0.0	0.8
Electricity contracts | Cost Of Sales | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	0.0			0.1	(0.1)	0.5
Electricity contracts | Selling And Administrative Expenses | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net	0.0			0.0	0.0	0.0
Foreign exchange contracts | Other Comprehensive Income | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net	(3.1)			1.9	23.9	1.4
Foreign exchange contracts | Cost Of Sales | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	6.1			(1.7)	12.5	(3.1)
Foreign exchange contracts | Selling And Administrative Expenses | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net	0.0			0.0	0.0	0.0
Designated as Hedging Instrument | Foreign exchange forward | Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivatives net settled | €			€ 126.5
Cash proceeds from settlement of hedge		$ 26.1
Designated as Hedging Instrument | Foreign exchange forward | Cost Of Sales | Fair Value Hedging
Derivative Instruments Gain Loss [Line Items]
Gain on derivative	1.9				7.4
Designated as Hedging Instrument | Foreign exchange forward | Maturity dates Through February 2018
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative | €							€ 334.0
Designated as Hedging Instrument | Foreign exchange forward | Maturity Dates Through 2015
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative | €							103.0
Designated as Hedging Instrument | Foreign exchange forward | Maturity Dates Through 2015 | Fair Value Hedging
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative | €			115.0				69.0
Not Designated as Hedging Instrument | Foreign exchange forward
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivatives net settled | €			€ 40.3
Cash proceeds from settlement of hedge		$ 11.8
Not Designated as Hedging Instrument | Foreign exchange forward | Maturity Dates Through February 2016
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative | €							€ 33.0
Not Designated as Hedging Instrument | Foreign exchange contracts | Cost Of Sales
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Recognized In Income Net	$ (0.5)			$ 0.9	$ 3.0	$ 1.1