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Income And Other Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income And Other Taxes [Abstract]
Reconciliation between income tax expense and theoretical U.S. tax rate, statutory rate	21.00%	21.00%	21.00%
Potential percentage decrease in unrecognized tax benefits	10.00%
Potential percentage increase in unrecognized tax benefits	10.00%
Interest expense on income tax reserves	$ (6)	$ 0	$ 3
Interest payable on income tax reserves	61	71
Valuation Allowance [Abstract]
Asset valuation allowances	2,731	1,924
Valuation allowance change from 2019 to 2020	807
US Tax Reform [Member]
Income And Other Taxes [Abstract]
Net deferred income tax expense (credits)/charges for tax rate and law changes	0	0	(291)
Total US and Non US
Income And Other Taxes [Abstract]
Net deferred income tax expense (credits)/charges for tax rate and law changes	(25)	$ (740)	$ (289)
AssetImpairments [Member]
Income And Other Taxes [Abstract]
Net deferred income tax expense (credits)/charges for tax rate and law changes	(6,300)
Change in net provisions [Member]
Valuation Allowance [Abstract]
Valuation allowance change from 2019 to 2020	762
Effects of foreign currency translation [Member]
Valuation Allowance [Abstract]
Valuation allowance change from 2019 to 2020	$ 41