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Derivative Financial Instruments and Hedging - Narrative (Details) € in Millions, lb in Millions, $ in Millions | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2019 USD ($) | Dec. 31, 2019 USD ($) lb | Dec. 31, 2017 USD ($) | Dec. 31, 2015 EUR (€) | Dec. 31, 2019 EUR (€)
Derivative Instruments and Hedging Activities Disclosure [Abstract] |  |  |  |  |
Percentage of estimated annual nickel requirements |  | 7.00% |  |  |
Derivative [Line Items] |  |  |  |  |
Tax expense for the recognition of a stranded deferred tax balance arising from deferred tax valuation allowances that was associated with a cash flow hedge portfolio | $ 6.0 |  |  |  |
Pre-tax cash flow hedge gain (loss) to be reclassified within twelve months |  | $ (0.9) |  |  |
Nickel [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative notional amount (in pounds of nickel) | lb |  | 7 |  |  |
Cash Flow Hedging [Member] | Natural gas contracts [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Percentage of forecasted natural gas usage hedged for 2021 |  | 50.00% |  |  |
Percentage Of Forecasted Natural Gas Usage Hedged for 2020 |  | 70.00% |  |  |
Cash Flow Hedging [Member] | Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Maturity Dates Through 2020 [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative notional amount | € |  |  |  |  | € 2.0
Fair Value Hedging [Member] | Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Maturity Dates Through 2017 [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional amount of derivatives entered during period | € |  |  |  | € 244.7 |
Cost of Sales [Member] | Fair Value Hedging [Member] | Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Gain (loss) on derivatives |  |  | $ 2.7 |  |
Term Loan due 2024 |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 4.21% | 4.21% |  |  | 4.21%
Term Loan due 2024 | Interest Rate Swap [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative notional amount | $ 50.0 | $ 50.0 |  |  |

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