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Multiemployer Pension Plans - Multiemployer Pension Plan Description and Contributions (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Multiemployer Pension Plan Disclosure [Line Items] |  |  |
Entity Tax Identification Number | 94-3030279 |  |
Contributions of the Company | $ 4.9 | $ 5.0 | $ 4.7
USW Plan |  |  |
Multiemployer Pension Plan Disclosure [Line Items] |  |  |
Entity Tax Identification Number | 23-6648508 |  |
Pension Protection Act Zone Status | Green | Green |
FIP/RP Status Pending/Implemented in 2020 | No |  |
Contributions of the Company | $ 3.8 | $ 3.8 | 3.6
Surcharge Imposed in 2020 | No |  |
USW Plan | Minimum |  |  |
Multiemployer Pension Plan Disclosure [Line Items] |  |  |
Expiration Date of Collective-Bargaining Agreement | Mar. 31, 2021 |  |
USW Plan | Maximum |  |  |
Multiemployer Pension Plan Disclosure [Line Items] |  |  |
Expiration Date of Collective-Bargaining Agreement | Sep. 30, 2025 |  |
Other Funds |  |  |
Multiemployer Pension Plan Disclosure [Line Items] |  |  |
Contributions of the Company | $ 1.1 | $ 1.2 | $ 1.1

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- Definition Expiration date of collective-bargaining arrangement (CBA) requiring contribution to multiemployer pension plan determined to be individually significant, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=35742348&loc=SL14450788-114948 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -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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- 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 -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=35742348&loc=SL14450788-114948 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (f)(1) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
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