Income Taxes - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) country	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Total Gross Unrecognized Tax Benefits
Valuation allowances	$ 2,342	$ 1,835
Deferred tax assets, operating loss carryforwards, foreign	319
Deferred tax liability not provided for temporary difference	6,000
Tax liabilities for gross unrecognized tax benefits	(454)	$ (451)	$ (472)
Interest accrued on income taxes for unrecognized tax benefits	95
Penalties accrued on income taxes for unrecognized tax benefits	23
Uncertain tax positions	572
Unrecognized tax benefits that would impact effective tax rate	523
Deferred tax asset that we did not prevail on all uncertain tax position	48
Deferred tax asset that we did not prevail on all uncertain tax position, foreign taxing jurisdiction	24
Deferred tax asset that we did not prevail on all uncertain tax position, increased valuation allowances	24
Uncertain tax positions, liabilities	$ 57
Number of countries in which entity operates (more than) | country	120
Foreign Net Operating Loss
Total Gross Unrecognized Tax Benefits
Valuation allowances	$ 1,657
US And Foreign Tax Credit Carryforward
Total Gross Unrecognized Tax Benefits
Valuation allowances	402
Other United States Net Operating Loss Tax Credit Carryforward
Total Gross Unrecognized Tax Benefits
Valuation allowances	55
Other US And Foreign Deferred Tax Assets
Total Gross Unrecognized Tax Benefits
Valuation allowances	228
Five year carryforward
Total Gross Unrecognized Tax Benefits
Operating loss carryforwards	$ 347
Expiration of operation loss carryforwards over the next 5 years	5 years
Six to twenty year carryforward
Total Gross Unrecognized Tax Benefits
Operating loss carryforwards	$ 960
Six to twenty year carryforward | Minimum
Total Gross Unrecognized Tax Benefits
Expiration of operation loss carryforwards over the next six to 20 years	6 years
Six to twenty year carryforward | Maximum
Total Gross Unrecognized Tax Benefits
Expiration of operation loss carryforwards over the next six to 20 years	20 years
Indefinite Foreign Tax
Total Gross Unrecognized Tax Benefits
Deferred tax assets, tax credit carryforwards, foreign	$ 402
Other Tax
Total Gross Unrecognized Tax Benefits
Deferred tax assets, tax credit carryforwards	$ 35