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
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value $ 12,938   $ 12,486
Other income      
Other Debt Securities Carried at Fair Value [Line Items]      
Unrealized mark-to-market net gains (losses) 41 $ 117  
Realized net gains (losses) (6) $ (103)  
Mortgage-backed securities      
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value 2,736   2,769
Agency-collateralized mortgage obligations      
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value 0   5
Non-agency residential      
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value 2,736   2,764
Non-U.S. securities      
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value 9,976   9,488
Other taxable securities, substantially all asset-backed securities      
Other Debt Securities Carried at Fair Value [Line Items]      
Other debt securities carried at fair value $ 226   $ 229