Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) assessment	Sep. 30, 2014	Sep. 30, 2015 USD ($) assessment	Sep. 30, 2014
Income Taxes [Line Items]
Effective income tax rate	31.10%	27.60%	28.70%	27.50%
Brazilian Federal Revenue Service [Member]
Income Taxes [Line Items]
Number of separate tax assessments | assessment	3		3
Estimated Tax Assessment Including Penalties and Interest	$ 347		$ 347
Estimated Additional Tax Assessment	40		40
Argentine Tax Authorities [Member]
Income Taxes [Line Items]
Estimated Additional Tax Assessment	286		286
Estimated Tax Assessment Including Interest	$ 91		$ 91