Derivative Financial Instruments and Hedging (Details2) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	$ 58.1	$ 59.9
Derivative Fair Value Of Derivative Liability	42.2	27.0
Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	58.1	53.5
Derivative Fair Value Of Derivative Liability	41.0	27.0
Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0	6.4
Derivative Fair Value Of Derivative Liability	1.2	0.0
Prepaid expenses and other current assets | Nickel and other raw material contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0	1.1
Prepaid expenses and other current assets | Foreign exchange contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	25.2	23.6
Prepaid expenses and other current assets | Foreign exchange contracts | Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0	6.4
Other assets | Nickel and other raw material contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0	0.5
Other assets | Foreign exchange contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	32.9	28.3
Accrued liabilities | Nickel and other raw material contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	10.7	5.8
Accrued liabilities | Natural gas contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	10.9	10.2
Accrued liabilities | Electricity contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	0.0	0.1
Accrued liabilities | Foreign exchange contracts | Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	1.2	0.0
Other long-term liabilities | Nickel and other raw material contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	10.5	3.0
Other long-term liabilities | Natural gas contracts | Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	$ 8.9	$ 7.9