v2.4.0.6
Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]    
Percent of revenue not exceeded by client 10.00%  
Auction rate securities $ 84 $ 94
After-tax future net revenue discount rate 10.00%  
Twelve month period prior to the end of the period for future net revenues calculation 12  
Estimated useful life range, years, maximum 39  
Estimated useful life range, years, minimum 3  
Maximum [Member]
   
Summary Of Significant Accounting Policies [Line Items]    
Mark-to-market threshold above which collateral must be posted 55  
Depletion calculation holding period, years 6  
Minimum [Member]
   
Summary Of Significant Accounting Policies [Line Items]    
Mark-to-market threshold above which collateral must be posted $ 0  
Depletion calculation holding period, years 3