Accumulated Other Comprehensive Income/(Loss) - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ 292,332
Net change	$ (2,814)	$ (4,765)	237	$ (19,050)
Ending balance	317,371	288,018	317,371	288,018
Accumulated other comprehensive income/(loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(14,290)	(14,369)	(17,341)	(84)
Net change	(2,814)	(4,765)	237	(19,050)
Ending balance	(17,104)	(19,134)	(17,104)	(19,134)
Unrealized gains/(losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(6,155)	(8,844)	(9,124)	2,640
Net change	(1,950)	(2,145)	1,019	(13,629)
Ending balance	(8,105)	(10,989)	(8,105)	(10,989)
After-tax unrealized gains/ (losses) related to HTM securities that have been transferred to AFS			(29)
After-tax unamortized unrealized gains/(losses) related to transfer of AFS securities to HTM			(1,000)	(1,300)
Translation adjustments, net of hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,278)	(1,675)	(1,545)	(934)
Net change	(340)	(581)	(73)	(1,322)
Ending balance	(1,618)	(2,256)	(1,618)	(2,256)
Fair value hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(43)	30	(33)	(131)
Net change	(5)	38	(15)	199
Ending balance	(48)	68	(48)	68
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(5,355)	(4,435)	(5,656)	(296)
Net change	(583)	(1,698)	(282)	(5,837)
Ending balance	(5,938)	(6,133)	(5,938)	(6,133)
Defined benefit pension and OPEB plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,512)	(123)	(1,451)	(210)
Net change	(21)	(1,004)	(82)	(917)
Ending balance	(1,533)	(1,127)	(1,533)	(1,127)
DVA on fair value option elected liabilities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	53	678	468	(1,153)
Net change	85	625	(330)	2,456
Ending balance	$ 138	$ 1,303	$ 138	$ 1,303