Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) assessment	Sep. 30, 2017	Sep. 30, 2018 USD ($) assessment	Sep. 30, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective income tax rate	15.20%	13.30%	14.30%	24.00%
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)	$ 13		$ 4
Brazilian Federal Revenue Service [Member]
Income Tax Contingency [Line Items]
Number of separate tax assessments | assessment	3		3
Income tax assessment	$ 105		$ 105
Income tax assessment - Interest and Penalties	295		295
Argentine Tax Authorities [Member]
Income Tax Contingency [Line Items]
Income tax assessment	16		16
Income tax assessment - Interest and Penalties	55		55
Estimated Additional Tax Assessment	45		45
Additional income tax assessment - Interest and Penalties	44		44
Tax and Customs Administration, Netherlands [Member]
Income Tax Contingency [Line Items]
Income tax assessment	94		94
Additional income tax assessment - Interest and Penalties	$ 28		$ 28