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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. 28, 2019
USD ($)
Dec. 29, 2018
USD ($)
Dec. 30, 2017
USD ($)
Dec. 28, 2019
USD ($)
Dec. 29, 2018
USD ($)
Dec. 28, 2019
potentially_responsible_party
Dec. 28, 2019
smelter_site
Site Contingency [Line Items]                  
Environmental expense     $ 1.7 $ 2.0 $ 7.5        
Environmental reserves     20.9 $ 23.6   $ 20.9 $ 23.6    
Expected environmental expenditures for 2020     0.8     0.8      
Expected environmental expenditures for 2021     0.7     0.7      
Expected environmental expenditures for 2022     0.6     0.6      
Expected environmental expenditures for 2023     0.8     0.8      
Expected environmental expenditures for 2024     0.7     0.7      
Expected environmental expenditures after 2024     17.3     17.3      
Lead Refinery Site [Member]                  
Lead Refinery Site [Abstract]                  
Site contingency, financial guarantee     1.0     1.0      
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     0.4     7.0      
Non-Operating Properties [Member] | Southeast Kansas Sites [Member]                  
Site Contingency [Line Items]                  
Environmental reserves     $ 5.6     $ 5.6      
Number of parties involved in settlement negotiations               2 3
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member]                  
Site Contingency [Line Items]                  
Period of permit, implementation of Best Management Practices     10 years            
Environmental remediation expense spending             1.9    
Estimated number of years until mitigation resolution     30 years            
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member] | Minimum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     $ 12.7            
Non-Operating Properties [Member] | Shasta Area Mine Sites [Member] | Maximum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     $ 17.7            
Non-Operating Properties [Member] | Lead Refinery Site [Member]                  
Site Contingency [Line Items]                  
Environmental expense             $ 0.7    
Estimated number of years until mitigation resolution     17 years            
Lead Refinery Site [Abstract]                  
EPA's estimated cost of site remediation   $ 26.0              
Number of surrounding properties | property   300              
Non-Operating Properties [Member] | Lead Refinery Site [Member] | Minimum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     $ 1.8            
Non-Operating Properties [Member] | Lead Refinery Site [Member] | Maximum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     2.3            
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member]                  
Site Contingency [Line Items]                  
Estimated number of years until mitigation resolution             6 years    
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member] | Minimum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     0.6            
Operating Properties [Member] | Mueller Copper Tube Products, Inc. [Member] | Maximum [Member]                  
Site Contingency [Line Items]                  
Mitigation estimates     $ 0.9