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Investment Securities (Details 1) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Amount of interest income from taxable and non-taxable investment securities      
Taxable $ 1,517 $ 1,292 $ 1,295
Non-taxable 303 309 311
Total interest income from investment securities $ 1,820 $ 1,601 $ 1,606