Quarterly report pursuant to Section 13 or 15(d)

Securities - U.S. GSE, Agency, and Treasury Securities (Details)

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Securities - U.S. GSE, Agency, and Treasury Securities (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity debt securities, Amortized Cost $ 49,577 $ 49,481
Held-to-maturity Securities, Fair Value 49,774 50,270
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
   
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity debt securities, Amortized Cost 135,056 121,522
Held-to-maturity Securities, Fair Value 136,203 123,933
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
   
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity debt securities, Amortized Cost 120,574 124,348
Held-to-maturity Securities, Fair Value 123,601 127,541
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
   
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity debt securities, Amortized Cost 28,423 22,995
Held-to-maturity Securities, Fair Value $ 28,738 $ 23,502