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Pension and Other Postretirement Benefits - Participation in Multi-Employer Pension Plans (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Retirement Benefits [Abstract] |  |  |
EIN | 236648508 |  |
PN | 499 |  |
Pension protection act zone status |  | Green | Green
Subject to financial improvement/rehabilitation plan | No |  |
Contributions of century aluminum company | $ 0.2 | $ 1.6 | $ 1.7
Withdrawal from Plan Probable | No |  |
Surcharge Imposed | No |  |
Expiration date of collective bargaining agreement | Mar. 31, 2026 |  |

X
- Definition Whether withdrawal from the multi-employer pension plan is probable. + References No definition available. + Details
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- Definition Indicates certified zone status of multiemployer pension plan determined to be individually significant. Acceptable values are "Green", "Yellow", "Orange", "Red", "Other", and "NA". + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Expiration date of collective-bargaining arrangement (CBA) requiring contribution to multiemployer pension plan determined to be individually significant, in YYYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Amount of cost for employer contribution to multiemployer pension plan determined to be individually significant. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Employer Identification Number (EIN) or Tax Identification Number (TIN) assigned by Internal Revenue Service (IRS) for multiemployer pension plan determined to be individually significant, in nine-digit numeric format. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Indicates whether funding improvement plan or rehabilitation plan was implemented or pending for multiemployer pension plan, determined to be individually significant. Acceptable values are "No", "Pending", "Implemented", "Other", and "NA". + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (f)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Plan number for multiemployer pension plan determined to be individually significant, in three-digit numeric format. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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- Definition Indicates whether employer paid surcharge to multiemployer pension plan determined to be individually significant. Acceptable values are "No", "Yes" and "NA". + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480547/715-80-55-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (f)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480576/715-80-50-5 + Details
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