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Risk Management, Derivative Instruments And Hedging Activities (Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Risk Management, Derivative Instruments And Hedging Activities [Abstract]    
Aggregate Fair Value Amounts of Derivative Instruments in a Net Liability Position $ 96 $ 148
Collateral Already Posted 36 2
Additional Cash Collateral or Letters of Credit in the Event Credit-risk-related Contingent Features were Triggered at the End of the Reporting Period $ 5 $ 14