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Investment Securities (Details 1) (USD $)
In Millions
3 Months Ended9 Months Ended
Sep. 30, 2011
Sep. 30, 2010
Sep. 30, 2011
Sep. 30, 2010
Amount of interest income from taxable and non-taxable investment securities    
Taxable$ 394$ 323$ 1,127$ 973
Non-taxable7677230231
Total interest income from investment securities$ 470$ 400$ 1,357$ 1,204