Quarterly report pursuant to Section 13 or 15(d)

Derivatives - Gains and Losses on Derivatives Designated as Fair Value Hedges (Details)

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Derivatives - Gains and Losses on Derivatives Designated as Fair Value Hedges (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative $ (1,937) $ 1,093 $ (3,951) $ 483
Hedged Item 1,756 (1,229) 3,676 (833)
Hedge Ineffectiveness   (136)   (350)
Interest rate risk on long-term debt | Interest expense        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative (869) 272 (3,174) (478)
Hedged Item 821 (422) 3,057 144
Hedge Ineffectiveness   (150)   (334)
Gain (loss) on derivatives 25   (39)  
Interest rate risk on long-term debt | Other income        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Gain (loss) on derivatives (1,000)   (576)  
Interest rate and foreign currency risk on long-term debt        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Hedge ineffectiveness and amounts excluded from effectiveness testing (83)   (130)  
Interest rate and foreign currency risk on long-term debt | Interest expense        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative (1,067) 901 (745) 1,024
Hedged Item 934 (877) 588 (1,010)
Hedge Ineffectiveness   24   14
Gain (loss) on derivatives   (124)   (281)
Interest rate and foreign currency risk on long-term debt | Other income        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Gain (loss) on derivatives   1,000   1,300
Interest rate risk on AFS securities | Interest income        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative (1) (80) (32) (63)
Hedged Item $ 1 70 $ 31 33
Hedge Ineffectiveness   $ (10)   $ (30)