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Multiemployer Pension Plans - Multiemployer Pension Plan Description and Contributions (Parenthetical) (Details) | 12 Months Ended
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Dec. 31, 2020 Agreement $ / shares
Multiemployer Pension Plan Disclosure [Line Items] |
Green zone funding percentage | 80.00%
USW Plan |
Multiemployer Pension Plan Disclosure [Line Items] |
Number of collective-bargaining agreements | Agreement | 3
USW Plan | Newark, Ohio and Spokane (Trentwood), Washington Facilities |
Multiemployer Pension Plan Disclosure [Line Items] |
Percentage of employees covered by bargaining agreement | 85.00%
USW Plan | Newark, Ohio and Spokane (Trentwood), Washington Facilities | Starting in July Two Thousand Twenty |
Multiemployer Pension Plan Disclosure [Line Items] |
Monthly contributions per hour worked by each bargaining unit employee | $ / shares | $ 1.75
USW Plan | Richmond (Bellwood), Virginia Facility |
Multiemployer Pension Plan Disclosure [Line Items] |
Percentage of employees covered by bargaining agreement | 12.00%
USW Plan | Florence, Alabama Facility |
Multiemployer Pension Plan Disclosure [Line Items] |
Percentage of employees covered by bargaining agreement | 3.00%

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- Definition Monthly contributions per hour worked by each bargaining unit employee. + References No definition available. + Details
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- Definition Percentage of entity's employees covered by collective-bargaining arrangement (CBA) to all entity's employees in multiemployer pension plan determined to be individually significant. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
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