Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) assessment	Sep. 30, 2016	Sep. 30, 2017 USD ($) assessment	Sep. 30, 2016
Income Tax Contingency [Line Items]
Effective income tax rate	13.30%	28.30%	24.00%	27.70%
Brazilian Federal Revenue Service [Member]
Income Tax Contingency [Line Items]
Number of separate tax assessments | assessment	3		3
Income tax assessment	$ 490		$ 490
Argentine Tax Authorities [Member]
Income Tax Contingency [Line Items]
Income tax assessment	128		128
Estimated Additional Tax Assessment	213		213
Tax and Customs Administration, Netherlands [Member]
Income Tax Contingency [Line Items]
Income tax assessment	$ 106		$ 106