Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income (Loss) - Change in Accumulated OCI (Details)

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Accumulated Other Comprehensive Income (Loss) - Change in Accumulated OCI (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance $ 267,146 $ 266,195  
Accounting change rated to certain tax effects 0    
Cumulative adjustment for adoption of new hedge accounting standard     $ 25
Net change (3,983) (28)  
Ending Balance 266,224 267,990  
Accumulated Other Comprehensive Income (Loss)      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (7,082) (7,288)  
Accounting change rated to certain tax effects (1,270)    
Cumulative adjustment for adoption of new hedge accounting standard     57
Net change (3,983) (28)  
Ending Balance (12,278) (7,316)  
Debit Valuation Adjustments      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (1,060) (767)  
Accounting change rated to certain tax effects (220)    
Cumulative adjustment for adoption of new hedge accounting standard     0
Net change 273 9  
Ending Balance (1,007) (758)  
Derivatives      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (831) (895)  
Accounting change rated to certain tax effects (189)    
Cumulative adjustment for adoption of new hedge accounting standard     57
Net change (275) 38  
Ending Balance (1,238) (857)  
Employee Benefit Plans      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (3,192) (3,480)  
Accounting change rated to certain tax effects (707)    
Cumulative adjustment for adoption of new hedge accounting standard     0
Net change 30 27  
Ending Balance (3,869) (3,453)  
Foreign currency      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (793) (879)  
Accounting change rated to certain tax effects 239    
Cumulative adjustment for adoption of new hedge accounting standard     0
Net change (48) (3)  
Ending Balance (602) (882)  
Debt and Equity Securities | Available-for-sale securities      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Beginning Balance (1,206) (1,267)  
Accounting change rated to certain tax effects (393)    
Cumulative adjustment for adoption of new hedge accounting standard     $ 0
Net change (3,963) (99)  
Ending Balance $ (5,562) $ (1,366)