v3.21.2
Shareholders' Equity - Accumulated Other Comprehensive Income/(Loss), Net of Tax (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance     $ 95,932  
Other comprehensive income/(loss) adjustments, net of tax $ (67) $ (294) (522) $ 849
Ending balance 106,297 92,650 106,297 92,650
Currency Translation [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (712) (677) (696) (616)
Other comprehensive income/(loss) adjustments, net of tax (20) (13) (36) (74)
Ending balance (732) (690) (732) (690)
Debt Valuation Adjustment [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (735) 124 (833) (572)
Other comprehensive income/(loss) adjustments, net of tax 67 (268) 165 428
Ending balance (668) (144) (668) (144)
Pension and Postretirement Liabilities [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (361) (339) (368) (342)
Other comprehensive income/(loss) adjustments, net of tax 0 (2) 7 1
Ending balance (361) (341) (361) (341)
Available-for-sale Securities [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (81) 551 463 46
Other comprehensive income/(loss) adjustments, net of tax (114) (11) (658) 494
Ending balance (195) 540 (195) 540
Accumulated Other Comprehensive Income (Loss) [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (1,889) (341) (1,434) (1,484)
Other comprehensive income/(loss) adjustments, net of tax (67) (294) (522) 849
Ending balance $ (1,956) $ (635) $ (1,956) $ (635)