Allowance for Credit Losses - Summary (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Allowance for Credit Losses
Beginning balance	$ 22,420	$ 19,726	$ 19,726
Gross charge-offs	7,674	5,096
Gross recoveries collected	(1,400)	(1,051)
Net charge-offs/(recoveries)	6,274	4,045
Provision for loan losses	7,798	6,843
Other	5	9
Ending balance	23,949	21,946	22,420
Allowance for lending-related commitments
Beginning balance	1,974	2,382	2,382
Provision for lending-related commitments	168	(308)
Other	0	1
Ending balance	2,142	2,075	1,974
Total allowance for investment securities	175	117	128
Total allowance for credit losses	26,266	24,138
Allowance for loan losses by impairment methodology
Asset-specific	(257)	(210)
Portfolio-based	24,206	22,156
Total allowance for loan losses	23,949	21,946	22,420
Loans by impairment methodology
Asset-specific	6,294	5,723
Portfolio-based	1,279,076	1,260,218
Total retained loans	1,285,370	1,265,941	1,280,870
Allowance for lending-related commitments by impairment methodology
Asset-specific	93	61
Portfolio-based	2,049	2,014
Total allowance for lending-related commitments	2,142	2,075	1,974
Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments [Abstract]
Asset-specific	619	387
Portfolio-based	541,077	545,182
Total lending-related commitments	541,696	545,569
CIB
Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments [Abstract]
Allowance for credit losses associated with accounts receivable	277	17
Collateral-dependent loans
Allowance for Credit Losses
Net charge-offs/(recoveries)	151	131
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	4,329	4,458
Cumulative effect of change in accounting principles | Accounting Standards Update 2022-02
Allowance for Credit Losses
Beginning balance		(587)	(587)
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Consumer, excluding credit card
Allowance for Credit Losses
Beginning balance	1,856	2,040	2,040
Gross charge-offs	971	809
Gross recoveries collected	(490)	(388)
Net charge-offs/(recoveries)	481	421
Provision for loan losses	360	723
Other	0	1
Ending balance	1,735	1,854	1,856
Allowance for lending-related commitments
Beginning balance	75	76	76
Provision for lending-related commitments	6	5
Other	0	0
Ending balance	81	81	75
Total allowance for credit losses	1,816	1,935
Allowance for loan losses by impairment methodology
Asset-specific	(756)	(942)
Portfolio-based	2,491	2,796
Total allowance for loan losses	1,735	1,854	1,856
Loans by impairment methodology
Asset-specific	2,784	3,321
Portfolio-based	375,154	393,733
Total retained loans	377,938	397,054	397,275
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0
Portfolio-based	81	81
Total allowance for lending-related commitments	81	81	75
Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments [Abstract]
Asset-specific	0	0
Portfolio-based	26,764	30,245
Total lending-related commitments	26,764	30,245
Credit card lending-related commitments not permitted to have an allowance for credit losses	18,600	18,100
Consumer, excluding credit card | Collateral-dependent loans
Allowance for Credit Losses
Net charge-offs/(recoveries)	1	4
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	2,805	3,384
Consumer, excluding credit card | Cumulative effect of change in accounting principles | Accounting Standards Update 2022-02
Allowance for Credit Losses
Beginning balance		(489)	(489)
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Credit card
Allowance for Credit Losses
Beginning balance	12,450	11,200	11,200
Gross charge-offs	6,044	3,852
Gross recoveries collected	(762)	(579)
Net charge-offs/(recoveries)	5,282	3,273
Provision for loan losses	6,932	4,073
Other	0	0
Ending balance	14,100	11,900	12,450
Allowance for lending-related commitments
Beginning balance	0	0	0
Provision for lending-related commitments	0	0
Other	0	0
Ending balance	0	0	0
Total allowance for credit losses	14,100	11,900
Allowance for loan losses by impairment methodology
Asset-specific	0	0
Portfolio-based	14,100	11,900
Total allowance for loan losses	14,100	11,900	12,450
Loans by impairment methodology
Asset-specific	0	0
Portfolio-based	219,542	196,935
Total retained loans	219,542	196,935
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0
Portfolio-based	0	0
Total allowance for lending-related commitments	0	0	0
Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments [Abstract]
Asset-specific	0	0
Portfolio-based	0	0
Total lending-related commitments	0	0
Credit card lending-related commitments not permitted to have an allowance for credit losses	989,600	898,900
Credit card | Collateral-dependent loans
Allowance for Credit Losses
Net charge-offs/(recoveries)	0	0
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	0	0
Credit card | Cumulative effect of change in accounting principles | Accounting Standards Update 2022-02
Allowance for Credit Losses
Beginning balance		(100)	(100)
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Wholesale
Allowance for Credit Losses
Beginning balance	8,114	6,486	6,486
Gross charge-offs	659	435
Gross recoveries collected	(148)	(84)
Net charge-offs/(recoveries)	511	351
Provision for loan losses	506	2,047
Other	5	8
Ending balance	8,114	8,192	8,114
Allowance for lending-related commitments
Beginning balance	1,899	2,306	2,306
Provision for lending-related commitments	162	(313)
Other	0	1
Ending balance	2,061	1,994	1,899
Total allowance for credit losses	10,175	10,186
Allowance for loan losses by impairment methodology
Asset-specific	499	732
Portfolio-based	7,615	7,460
Total allowance for loan losses	8,114	8,192	8,114
Loans by impairment methodology
Asset-specific	3,510	2,402
Portfolio-based	684,380	669,550
Total retained loans	687,890	671,952	672,472
Allowance for lending-related commitments by impairment methodology
Asset-specific	93	61
Portfolio-based	1,968	1,933
Total allowance for lending-related commitments	2,061	1,994	1,899
Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments [Abstract]
Asset-specific	619	387
Portfolio-based	514,313	514,937
Total lending-related commitments	514,932	515,324
Credit card lending-related commitments not permitted to have an allowance for credit losses	26,600	16,200
Wholesale | Collateral-dependent loans
Allowance for Credit Losses
Net charge-offs/(recoveries)	150	127
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	$ 1,524	1,074
Wholesale | Cumulative effect of change in accounting principles | Accounting Standards Update 2022-02
Allowance for Credit Losses
Beginning balance		$ 2	$ 2
Allowance for loan losses by impairment methodology
Total allowance for loan losses