Annual report pursuant to Section 13 and 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
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance $ 267,146 $ 266,195 $ 255,615  
Accounting change rated to certain tax effects 0      
Cumulative adjustment for adoption of hedge accounting standard       $ 25
Net change (3,916) 206 (1,930)  
Ending Balance 265,325 267,146 266,195  
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (7,082) (7,288) (5,358)  
Accounting change rated to certain tax effects (1,270)      
Cumulative adjustment for adoption of hedge accounting standard       57
Net change (3,916) 206 (1,930)  
Ending Balance (12,211) (7,082) (7,288)  
Debt and Equity Securities        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (1,206) (1,267) 78  
Accounting change rated to certain tax effects (393)      
Cumulative adjustment for adoption of hedge accounting standard       0
Net change (3,953) 61 (1,345)  
Ending Balance (5,552) (1,206) (1,267)  
Debit Valuation Adjustments        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (1,060) (767) (611)  
Accounting change rated to certain tax effects (220)      
Cumulative adjustment for adoption of hedge accounting standard       0
Net change 749 (293) (156)  
Ending Balance (531) (1,060) (767)  
Derivatives        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (831) (895) (1,077)  
Net change   64 182  
Ending Balance (1,000) (831) (895)  
Derivatives        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Accounting change rated to certain tax effects (189)      
Cumulative adjustment for adoption of hedge accounting standard       57
Net change (53)      
Ending Balance (1,016)      
Employee Benefit Plans        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (3,192) (3,480) (2,956)  
Accounting change rated to certain tax effects (707)      
Cumulative adjustment for adoption of hedge accounting standard       0
Net change (405) 288 (524)  
Ending Balance (4,304) (3,192) (3,480)  
Foreign currency        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning Balance (793) (879) (792)  
Accounting change rated to certain tax effects 239      
Cumulative adjustment for adoption of hedge accounting standard       $ 0
Net change (254) 86 (87)  
Ending Balance $ (808) $ (793) $ (879)