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Summary Of Significant Accounting Policies (Equity Changes Attributable To Noncontrolling Interest) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Summary Of Significant Accounting Policies [Abstract]    
Noncontrolling interest, beginning of period $ 149  
Net income attributable to noncontrolling interest   3
Dividends paid to noncontrolling interest holders (2) (2)
Noncontrolling interest, end of period $ 147