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 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative $ (1,299) $ 326 $ (5,250) $ 809
Hedged Item 1,317 (417) 4,993 (1,250)
Hedge Ineffectiveness   (91)   (441)
Interest rate risk on long-term debt | Interest expense        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative (1,129) (273) (4,303) (751)
Hedged Item 1,122 169 4,179 313
Hedge Ineffectiveness   (104)   (438)
Gain (loss) on derivatives (117)   (156)  
Interest rate risk on long-term debt | Other income        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Gain (loss) on derivatives (96)   (672)  
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 31   (99)  
Interest rate and foreign currency risk on long-term debt | Interest expense        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative (182) 607 (927) 1,631
Hedged Item 207 (593) 795 (1,603)
Hedge Ineffectiveness   14   28
Gain (loss) on derivatives   (29)   (310)
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   635   1,900
Interest rate risk on AFS securities | Interest income        
Effect of Fair Value Hedges on Results of Operations [Abstract]        
Derivative 12 (8) (20) (71)
Hedged Item $ (12) 7 $ 19 40
Hedge Ineffectiveness   $ (1)   $ (31)