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Contingencies - Additional Information (Detail) - USD ($)
9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Site Contingency [Line Items]      
Environmental losses accrual $ 22,448,000   $ 25,905,000
Cash expenditures related to legal and environmental matters $ 3,781,000 $ 2,826,000  
Contribution for future response costs 5.00%    
Wilmington Site [Member]      
Site Contingency [Line Items]      
Payment of environmental response costs $ 2,965,000    
Minimum [Member]      
Site Contingency [Line Items]      
Environmental and legal losses 22,448,000    
Maximum [Member]      
Site Contingency [Line Items]      
Environmental and legal losses $ 41,146,000