Accumulated Other Comprehensive Income/(Loss) - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ 327,878
Net change	$ 4,554	$ (2,814)	3,659	$ 237
Ending balance	345,836	317,371	345,836	317,371
Accumulated other comprehensive income/(loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(11,338)	(14,290)	(10,443)	(17,341)
Net change	4,554	(2,814)	3,659	237
Ending balance	(6,784)	(17,104)	(6,784)	(17,104)
Unrealized gains/(losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(3,494)	(6,155)	(3,743)	(9,124)
Net change	2,297	(1,950)	2,546	1,019
Ending balance	(1,197)	(8,105)	(1,197)	(8,105)
After-tax unamortized unrealized gains/(losses) related to AFS securities transferred to HTM			(661)	(1,000)
After-tax unrealized gains/ (losses) related to HTM securities transferred to AFS				(29)
Translation adjustments, net of hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,576)	(1,278)	(1,216)	(1,545)
Net change	389	(340)	29	(73)
Ending balance	(1,187)	(1,618)	(1,187)	(1,618)
Fair value hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(147)	(43)	(134)	(33)
Net change	(20)	(5)	(33)	(15)
Ending balance	(167)	(48)	(167)	(48)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,843)	(5,355)	(3,932)	(5,656)
Net change	2,265	(583)	1,354	(282)
Ending balance	(2,578)	(5,938)	(2,578)	(5,938)
Defined benefit pension and OPEB plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,055)	(1,512)	(1,078)	(1,451)
Net change	(28)	(21)	(5)	(82)
Ending balance	(1,083)	(1,533)	(1,083)	(1,533)
DVA on fair value option elected liabilities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(223)	53	(340)	468
Net change	(349)	85	(232)	(330)
Ending balance	$ (572)	$ 138	$ (572)	$ 138