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Fair Values of Financial Instruments (Details 3) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Fair Values of Financial Instruments (Additional Textual) [Abstract]    
Percentage of fair value amounts for fixed maturities provided by a pricing service 99.00%  
Other Postretirement Benefits [Member]
   
Fair Values of Financial Instruments (Textual) [Abstract]    
Plan assets at fair value $ 73 $ 65