Fair Value (Quantitative Information) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ (139)	$ (126)	$ (24)	$ 48	$ (108)	$ 5
Interest Rate Contract [Member]
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ (421)	(416)	(304)	(191)	(302)	(210)
Interest Rate Contract [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Fair Value Inputs, Entity Credit Risk	2.90%
Interest Rate Contract [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Fair Value Inputs, Entity Credit Risk	11.20%
Interest Rate Contract [Member] | Weighted Average [Member]
Fair Value Inputs [Abstract]
Fair Value Inputs, Entity Credit Risk	4.40%
Foreign Exchange Contract [Member]
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ 271	$ 290	$ 277	222	223	$ 209
Cross currency derivatives [Member]
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs				$ 0	$ (33)
Argentina, Pesos | Foreign Exchange Contract [Member]
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ 271
Argentina, Pesos | Foreign Exchange Contract [Member] | Minimum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 1 year	18.6
Argentina, Pesos | Foreign Exchange Contract [Member] | Maximum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 1 year	35.2
Argentina, Pesos | Foreign Exchange Contract [Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 1 year	26.8
Other unspecified currency [Domain] | Foreign Exchange Contract [Member]
Fair Value Inputs Quantitative Information [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	$ 11