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Long-Term Debt (Revenue Bonds) (Details) - Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] - Senior Notes [Member] - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 11 $ 11
Debt Instrument, Interest Rate, Effective Percentage 0.14% 1.78%