Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) assessment	Jun. 30, 2016	Jun. 30, 2017 USD ($) assessment	Jun. 30, 2016
Income Tax Contingency [Line Items]
Effective income tax rate	28.20%	29.20%	26.90%	27.30%
Brazilian Federal Revenue Service [Member]
Income Tax Contingency [Line Items]
Number of separate tax assessments | assessment	3		3
Income tax assessment	$ 464		$ 464
Argentine Tax Authorities [Member]
Income Tax Contingency [Line Items]
Income tax assessment	130		130
Estimated Additional Tax Assessment	210		210
Tax and Customs Administration, Netherlands [Member]
Income Tax Contingency [Line Items]
Income tax assessment	$ 103		$ 103