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Debt - Lines of Credit (Details) - USD ($)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2020
Mar. 31, 2019
Mar. 27, 2020
Mar. 26, 2020
Debt          
Payments to acquire pollution control bond $ 212,760,000 $ 212,760,000 $ 0    
Line of Credit          
Debt          
Maximum borrowing capacity 1,200,000,000 1,200,000,000      
Borrowings under lines of credit   $ 180,000,000      
Line of Credit | JPMorgan Chase          
Debt          
Maximum borrowing capacity       $ 363,000,000 $ 150,000,000
Borrowings under lines of credit $ 213,000,000