Quarterly report pursuant to Section 13 or 15(d)

Securities - Other Debt Securities Carried at Fair Value (Details)

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Securities - Other Debt Securities Carried at Fair Value (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value $ 16,562   $ 16,562   $ 19,720
Other income          
Other Debt Securities Carried at Fair Value [Line Items]          
Unrealized mark-to-market net gains (losses) 124 $ 47 323 $ (25)  
Realized net gains (losses) (11) $ (28) (129) $ (65)  
Agency-collateralized mortgage obligations          
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value 5   5   5
Non-agency residential          
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value 3,058   3,058   3,139
Mortgage-backed securities          
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value 3,063   3,063   3,144
Non-U.S. securities          
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value 13,260   13,260   16,336
Other taxable securities, substantially all asset-backed securities          
Other Debt Securities Carried at Fair Value [Line Items]          
Other debt securities carried at fair value $ 239   $ 239   $ 240