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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