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Supplemental Data (Summary of Accounts Receivable, Net) (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Supplemental Data (Millions of dollars) [Abstract]    
From customers $ 2,131 $ 2,050
Other 181 167
Less allowance for doubtful accounts and sales discounts (49) (53)
Total $ 2,263 $ 2,164