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Investments (details) - Impairment Charges (USD $)
In Millions
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Impairment charges        
Impairment charges $ 4 $ 4 $ 8 $ 14
Fixed maturities [Member]
       
Impairment charges        
Impairment charges 3 1 7 7
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
       
Impairment charges        
Impairment charges 2 1 4 2
All other corporate bonds [Member]
       
Impairment charges        
Impairment charges 1   3 5
Equity securities [Member]
       
Impairment charges        
Impairment charges 1 1 1 2
Equity securities, common stock [Member]
       
Impairment charges        
Impairment charges 1 1 1 2
Other investments [Member]
       
Impairment charges        
Impairment charges   $ 2   $ 5