Revenues - Trade Accounts And Allowance for Doubtful Accounts (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 67
Current-period provision for expected credit losses	10
Write-offs charged against the allowance	(2)
Ending Balance	74
Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ (1)