Percentage Of Forecasted Natural Gas Usage Hedged for Year 1

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Aggregate notional amount of price risk derivatives for instruments with notional amounts expressed in percentage of estimated annual domestic (U.S.) usage

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Aggregate notional amount of price risk derivatives for instruments with notional amounts expressed in percentage of annual estimated usage in production

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The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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Nominal mass used to calculate payments on a derivative instrument.

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Nominal or face amount used to calculate payment on derivative.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Derivative Financial Instruments and Hedging (Details) € in Millions, lb in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) lb	Mar. 31, 2019 USD ($)	Mar. 31, 2020 EUR (€)
Derivative Instruments Gain Loss [Line Items]
Percentage of estimated annual nickel requirements	6.00%
Percentage Of Forecasted Natural Gas Usage Hedged for 2020	70.00%
Percentage Of Forecasted Natural Gas Usage Hedged for 2021	50.00%
Net derivatives (loss) gain on hedge transactions	$ (12.3)	$ 10.5
Reclassification of Cash Flow Hedge Gain (Loss) [Abstract]
Cash Flow Hedge Gain (Loss) To Be Reclassified Within Twelve Months	(8.1)
Other Comprehensive Income (Loss) [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Net derivatives (loss) gain on hedge transactions	(9.4)	8.0
Cost of Sales and Interest Expense [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	$ (1.4)	(0.7)
Nickel
Derivative Instruments Gain Loss [Line Items]
Notional amount of nickel hedge (in pounds of nickel) \| lb	6
Interest Rate Swap \| Other Comprehensive Income (Loss) [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Net derivatives (loss) gain on hedge transactions	$ (1.9)	(0.2)
Interest Rate Swap \| Interest Expense [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	(0.2)	(0.1)
Nickel and other raw material contracts \| Other Comprehensive Income (Loss) [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Net derivatives (loss) gain on hedge transactions	(6.2)	8.3
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	(0.2)	(0.4)
Natural gas contracts \| Other Comprehensive Income (Loss) [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Net derivatives (loss) gain on hedge transactions	(1.2)	(0.4)
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	(1.0)	0.1
Foreign exchange contracts \| Other Comprehensive Income (Loss) [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Net derivatives (loss) gain on hedge transactions	(0.1)	0.3
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	0.0	(0.3)
Designated as Hedging Instrument \| Foreign exchange forward \| Maturity Dates Through 2020 [Member] \| Cash Flow Hedging
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative \| €			€ 2
Not Designated as Hedging Instrument \| Foreign exchange forward
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative \| €			€ 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	$ 0.0	$ 0.1
2024 Term Loan
Derivative Instruments Gain Loss [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.21%		4.21%
2024 Term Loan \| Interest Rate Swap
Derivative Instruments Gain Loss [Line Items]
Notional amount of derivative	$ 50.0