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Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Document Period End Date Dec. 31, 2020  
Carrying Value $ 171 $ 170
Equity Securities, FV-NI and without Readily Determinable Fair Value 0 0
Insurance contracts in nonqualified pension trusts, carrying amount 30 35
Insurance contracts in nonqualified pension trusts, fair value 31 35
Long-term debt, including current installments of long-term debt, carrying amount 3,671 3,455
Long-term debt, including current installments of long-term debt, fair value 3,845 3,599
Significant Other Observable Inputs (Level 2) [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity Securities, FV-NI and without Readily Determinable Fair Value 0 0
Insurance contracts in nonqualified pension trusts, fair value 31 35
Long-term debt, including current installments of long-term debt, fair value 3,644 3,456
Unobservable Inputs (Level 3) [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity Securities, FV-NI and without Readily Determinable Fair Value 0 0
Insurance contracts in nonqualified pension trusts, fair value 0 0
Long-term debt, including current installments of long-term debt, fair value $ 201 $ 143