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Commitments and Contingencies - Environmental (Details) $ in Millions | 1 Months Ended | 12 Months Ended | 24 Months Ended | 36 Months Ended |
--- | --- | --- | --- | --- | ---
Jan. 31, 2018 USD ($) unilateral_administrative_order | Sep. 30, 2014 USD ($) property | Dec. 26, 2020 USD ($) | Dec. 28, 2019 USD ($) | Dec. 29, 2018 USD ($) | Dec. 28, 2019 USD ($) | Dec. 26, 2020 USD ($) | Dec. 28, 2019 USD ($) | Dec. 26, 2020 smelter_site | Dec. 26, 2020 potentially_responsible_party
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Environmental expense |  |  | $ 4.2 | $ 1.7 | $ 2.0 |  |  |  |  |
Environmental reserves |  |  | 24.0 | $ 20.9 |  | $ 20.9 | $ 24.0 | $ 20.9 |  |
Expected environmental expenditures for 2021 |  |  | 2.7 |  |  |  | 2.7 |  |  |
Expected environmental expenditures for 2022 |  |  | 0.8 |  |  |  | 0.8 |  |  |
Expected environmental expenditures for 2023 |  |  | 0.8 |  |  |  | 0.8 |  |  |
Expected environmental expenditures for 2024 |  |  | 0.9 |  |  |  | 0.9 |  |  |
Expected environmental expenditures for 2025 |  |  | 0.8 |  |  |  | 0.8 |  |  |
Expected environmental expenditures after 2025 |  |  | 18.0 |  |  |  | 18.0 |  |  |
East La Harpe [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Number of parties involved in settlement negotiations |  |  |  |  |  |  |  |  | 3 | 2
Southeast Kansas Sites [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Environmental reserves |  |  | $ 5.6 |  |  |  | 5.6 |  |  |
Number of parties involved in settlement negotiations | smelter_site |  |  |  |  |  |  |  |  | 3 |
Shasta Area Mine Sites [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Period of permit, implementation of Best Management Practices |  |  | 10 years |  |  |  |  |  |  |
Environmental remediation expense spending |  |  |  |  |  |  |  | $ 1.7 |  |
Estimated number of years until mitigation resolution |  |  | 30 years |  |  |  |  |  |  |
Shasta Area Mine Sites [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | $ 13.9 |  |  |  |  |  |  |
Shasta Area Mine Sites [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | 18.0 |  |  |  |  |  |  |
Lead Refinery Site [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Environmental expense |  |  |  |  |  |  | 0.6 |  |  |
Lead Refinery Site [Abstract] |  |  |  |  |  |  |  |  |  |
EPA's estimated cost of site remediation |  | $ 26.0 |  |  |  |  |  |  |  |
Number of surrounding properties | property |  | 300 |  |  |  |  |  |  |  |
Site contingency, financial guarantee |  |  | 1.0 |  |  |  | $ 1.0 |  |  |
Lead Refinery Site [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | 1.7 |  |  |  |  |  |  |
Lead Refinery Site [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | 2.4 |  |  |  |  |  |  |
Lead Refinery NPL Site [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Environmental reserves | $ 4.5 |  |  |  |  |  |  |  |  |
Lead Refinery Site [Abstract] |  |  |  |  |  |  |  |  |  |
Number of UAOs issued | unilateral_administrative_order | 2 |  |  |  |  |  |  |  |  |
Site contingency, total costs | $ 25.0 |  |  |  |  |  |  |  |  |
Site contingency, amount agreed upon to pay PRPs for past costs | $ 2.0 |  |  |  |  |  |  |  |  |
Possible further payments for ongoing work by PRPs |  |  | 0.7 |  |  |  |  |  |  |
Payments for unilateral administrative orders |  |  |  |  |  | $ 7.2 |  |  |  |
Mueller Copper Tube Products, Inc. [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | 0.9 |  |  |  |  |  |  |
Mueller Copper Tube Products, Inc. [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Site Contingency [Line Items] |  |  |  |  |  |  |  |  |  |
Mitigation estimates |  |  | $ 1.1 |  |  |  |  |  |  |

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