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Schedule Of Valuation And Qualifying Accounts (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Presented in Consolidated Statements of Financial Position [Abstract]      
Allowance for doubtful accounts - current $ 17 $ 4  
Allowance for doubtful accounts - long-term 51 35  
Accrued casualty costs, current 177 190  
Accrued Casualty Costs [Member]      
Schedule Of Valuation And Qualifying Accounts [Line Items]      
Balance, beginning of period 657 709 $ 684
Charges/(reduction) to expense 231 215 202
Net recoveries/(write-offs), cash payments and other reductions (244) (267) (177)
Balance, end of period 644 657 709
Presented in Consolidated Statements of Financial Position [Abstract]      
Accrued casualty costs, current 177 190 211
Accrued casualty costs, long-term 467 467 498
Balance, end of period $ 644 $ 657 $ 709