Income Taxes - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) country	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Total Gross Unrecognized Tax Benefits
Tax Cuts and Jobs Act, tax expense (benefit)	$ (107)
Operating loss carryforwards	1,525	$ 1,376
Valuation allowances	2,372	2,484
Deferred tax assets, operating loss carryforwards, foreign	206
Tax Cuts and Jobs Act, accrued foreign withholding taxes	9
Deferred tax liability not provided for temporary difference	6,300
Tax liabilities for gross unrecognized tax benefits	472	$ 395	$ 94
Interest accrued on income taxes for unrecognized tax benefits	91
Penalties accrued on income taxes for unrecognized tax benefits	34
Uncertain tax positions	597
Unrecognized tax benefits that would impact effective tax rate	516
Deferred tax asset that we did not prevail on all uncertain tax position	81
Deferred tax asset that we did not prevail on all uncertain tax position, foreign taxing jurisdiction	21
Deferred tax asset that we did not prevail on all uncertain tax position, increased valuation allowances	60
Uncertain tax positions, liabilities	96
Uncertain tax positions, assets	$ 1
Number of countries in which entity operates (more than) | country	120
Foreign Net Operating Loss
Total Gross Unrecognized Tax Benefits
Valuation allowances	$ 1,253
US And Foreign Tax Credit Carryforward
Total Gross Unrecognized Tax Benefits
Valuation allowances	607
Other United States Net Operating Loss Tax Credit Carryforward
Total Gross Unrecognized Tax Benefits
Valuation allowances	84
Other US And Foreign Deferred Tax Assets
Total Gross Unrecognized Tax Benefits
Valuation allowances	428
Five year carryforward
Total Gross Unrecognized Tax Benefits
Operating loss carryforwards	$ 319
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	$ 186
Minimum | Six to twenty year carryforward
Total Gross Unrecognized Tax Benefits
Expiration of operation loss carryforwards over the next six to 20 years	6 years
Maximum | Six to twenty year carryforward
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	$ 141
Definite Foreign Tax
Total Gross Unrecognized Tax Benefits
Deferred tax assets, tax credit carryforwards, foreign	466
Other Tax
Total Gross Unrecognized Tax Benefits
Deferred tax assets, tax credit carryforwards	$ 46