Fair Value (Quantitative Information) (Details) (USD $)

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Assets Liabilities Value

$ (396,000,000)

$ (148,000,000)

$ 49,000,000

Interest Rate Derivatives

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Assets Liabilities Value

(412,000,000)

(128,000,000)

(1,000,000)

Interest Rate Derivatives | Minimum

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Subsidiaries' credit risk

2.60%

Interest Rate Derivatives | Maximum

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Subsidiaries' credit risk

9.80%

Interest Rate Derivatives | Weighted Average

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Subsidiaries' credit risk

6.50%

Foreign Currency Embedded Derivative Argentine Peso [Member]

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Assets Liabilities Value

69,000,000

Foreign Currency Embedded Derivative Argentine Peso [Member] | Minimum

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Argentine Peso to U.S. Dollar currency exchange rate after 2 years

10.50

Foreign Currency Embedded Derivative Argentine Peso [Member] | Maximum

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Argentine Peso to U.S. Dollar currency exchange rate after 2 years

15.40

Foreign Currency Embedded Derivative Argentine Peso [Member] | Weighted Average

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Argentine Peso to U.S. Dollar currency exchange rate after 2 years

12.90

Commodity And Other Derivative Other [Member]

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Assets Liabilities Value

2,000,000

Commodity And Other Embedded Derivative Aluminum [Member]

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Assets Liabilities Value

(55,000,000)

Commodity And Other Embedded Derivative Aluminum [Member] | Minimum

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Market Price of Power for Customer in Cameroon (per KWh)

0.09

Commodity And Other Embedded Derivative Aluminum [Member] | Maximum

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

Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]

Market Price of Power for Customer in Cameroon (per KWh)

$ 0.13