Fair Value (Quantitative Information) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	$ (49)	$ (69)	$ (396)	$ (286)	$ (122)	$ (148)
Interest rate derivatives [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(63)	(72)	(412)	(281)	(124)	(128)
Interest rate derivatives [Member] | Minimum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Subsidiaries' credit risk	3.13%
Interest rate derivatives [Member] | Maximum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Subsidiaries' credit risk	5.95%
Interest rate derivatives [Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Subsidiaries' credit risk	4.47%
Foreign Currency Embedded Derivative Argentine Peso [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	77
Foreign Currency Embedded Derivative Argentine Peso [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 3 years	18.15
Foreign Currency Embedded Derivative Argentine Peso [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 3 years	31.85
Foreign Currency Embedded Derivative Argentine Peso [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 3 years	25.68
Foreign Currency Embedded Derivative Other [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(7)
Commodity and Other Embedded Derivative Aluminum [ Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(65)
Commodity and Other Embedded Derivative Aluminum [ Member] | Minimum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Market Price of Power for Customer in Cameroon (per KWh)	0.06
Commodity and Other Embedded Derivative Aluminum [ Member] | Maximum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Market Price of Power for Customer in Cameroon (per KWh)	0.14
Commodity and Other Embedded Derivative Aluminum [ Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Market Price of Power for Customer in Cameroon (per KWh)	0.12
Commodity And Other Embedded Derivative Other [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	$ 9