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Debt - Activity (Details) - USD ($) | Dec. 31, 2023 | Dec. 31, 2022 | Apr. 14, 2021 | Apr. 09, 2021
--- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |
Total | $ 479,200,000 | $ 527,700,000 |  |
Industrial Revenue Bonds, Variable |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum variable interest rate | 12.00% |  |  |
Industrial revenue bonds due 2028 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Hancock County industrial revenue bonds ("IRBs") due April 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) | $ 7,800,000 | 7,800,000 |  |
Stated interest rate | 4.00% |  |  |
Senior Notes | Senior Secured Notes, 7.5% |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Financing fees | $ 2,600,000 |  |  |
Stated interest rate | 7.50% |  | 7.50% |
7.5% senior secured notes due April 1, 2028, net of financing fees of $2.6 million at December 31, 2023, interest payable semiannually | $ 247,400,000 | 246,600,000 |  |
Senior Notes | Senior Convertible Notes, 2.75% |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Financing fees | 1,500,000 |  |  |
Stated interest rate |  |  |  | 2.75%
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.5 million at December 31, 2023, interest payable semiannually | 84,700,000 | 84,400,000 |  |
U.S revolving credit facility | Revolving Credit Facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Revolving credit facility | $ 23,700,000 | 90,000,000.0 |  |
Stated interest rate | 9.25% |  |  |
Foreign line of credit | Revolving Credit Facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Revolving credit facility | $ 0 | 35,000,000.0 |  |
Foreign line of credit | Casthouse Facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Revolving credit facility | 5,500,000 | 0 |  |
Financing fees | 700,000 |  |  |
Secured debt | $ 98,800,000 | 49,400,000 |  |
Stated interest rate | 8.86% |  |  |
Foreign line of credit | Iceland Term Facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Revolving credit facility | $ 1,300,000 | 13,300,000 |  |
Financing fees | 0 |  |  |
Secured debt | $ 0 | 1,200,000 |  |
Stated interest rate | 3.20% |  |  |
Effective interest rate (percent) | 7.05% |  |  |
Foreign line of credit | Vlissingen Facility Agreement |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Revolving credit facility | $ 10,000,000.0 | $ 0 |  |
Secured debt | $ 10,000,000.0 |  |  |
Stated interest rate | 8.75% |  |  |

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