v3.21.2
Shareholders' Equity - Accumulated Other Comprehensive Income/(Loss), Net of Tax (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance     $ 95,932  
Other comprehensive income/(loss) adjustments, net of tax $ 185 $ (2,278) (455) $ 1,143
Ending balance 101,890 90,029 101,890 90,029
Currency Translation [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (696) (633) (696) (616)
Other comprehensive income/(loss) adjustments, net of tax (16) (44) (16) (61)
Ending balance (712) (677) (712) (677)
Debt Valuation Adjustment [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (852) 2,342 (833) (572)
Other comprehensive income/(loss) adjustments, net of tax 117 (2,218) 98 696
Ending balance (735) 124 (735) 124
Pension and Postretirement Liabilities [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (361) (335) (368) (342)
Other comprehensive income/(loss) adjustments, net of tax   (4) 7 3
Ending balance (361) (339) (361) (339)
Available-for-sale Securities [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (165) 563 463 46
Other comprehensive income/(loss) adjustments, net of tax 84 (12) (544) 505
Ending balance (81) 551 (81) 551
Accumulated Other Comprehensive Income (Loss) [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (2,074) 1,937 (1,434) (1,484)
Other comprehensive income/(loss) adjustments, net of tax 185 (2,278) (455) 1,143
Ending balance $ (1,889) $ (341) $ (1,889) $ (341)