Accumulated Other Comprehensive Income/(Loss) - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 362,438
Net change	(2,399)	$ 3,345
Ending balance	364,038	351,420
Accumulated other comprehensive income/(loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,290)	(12,456)
Net change	(2,399)	3,345
Ending balance	(6,689)	(9,111)
Unrealized gains/(losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(261)	(3,830)
Net change	(2,401)	953
Ending balance	(2,662)	(2,877)
After-tax unamortized unrealized losses related to AFS securities transferred to HTM	(297)	(639)
Translation adjustments, net of hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(735)	(2,074)
Net change	(167)	489
Ending balance	(902)	(1,585)
Fair value hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(157)	(221)
Net change	41	28
Ending balance	(116)	(193)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,426)	(4,814)
Net change	(901)	1,674
Ending balance	(2,327)	(3,140)
Defined benefit pension and OPEB plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(562)	(1,141)
Net change	4	(16)
Ending balance	(558)	(1,157)
DVA on fair value option elected liabilities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,149)	(376)
Net change	1,025	217
Ending balance	$ (124)	$ (159)