Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) assessment	Jun. 30, 2017	Jun. 30, 2018 USD ($) assessment	Jun. 30, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective income tax rate	13.20%	28.20%	13.80%	26.90%
Out of period tax discrete expense (income) items charged (credited) to earnings			$ 39
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%		35.00%
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	$ 5		$ (9)
Brazilian Federal Revenue Service [Member]
Income Tax Contingency [Line Items]
Number of separate tax assessments | assessment	3		3
Income tax assessment	$ 109		$ 109
Income tax assessment - Interest and Penalties	303		303
Argentine Tax Authorities [Member]
Income Tax Contingency [Line Items]
Income tax assessment	23		23
Income tax assessment - Interest and Penalties	75		75
Estimated Additional Tax Assessment	64		64
Additional income tax assessment - Interest and Penalties	58		58
Tax and Customs Administration, Netherlands [Member]
Income Tax Contingency [Line Items]
Income tax assessment	95		95
Additional income tax assessment - Interest and Penalties	$ 29		$ 29