Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Allowance for Credit Losses and Reserve for Unfunded Lending Commitments Activity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			$ 13,240
Provision for credit losses	$ 2,284	$ 1,669	7,569	$ 3,431
Balance at the end of the period	14,955		14,955
Financing Receivable Allowance For Credit Loss Translation Adjustments And Purchase Credit Deteriorated Loans	0	10	32	10
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	14,646	11,491	13,240	11,430
Financing Receivable, Allowance for Credit Loss, Writeoff	(2,581)	(1,470)	(7,596)	(4,174)
Recoveries	582	539	1,715	1,631
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery	(1,999)	(931)	(5,881)	(2,543)
Provision for credit losses	2,321	1,665	7,626	3,358
Allowance build (release) for credit losses	322	734	1,745	815
Other changes	(13)	(16)	33	(36)
Balance at the end of the period	14,955	12,209	14,955	12,209
Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	197	239	218	165
Provision for credit losses	(39)	4	(60)	78
Balance at the end of the period	158	243	158	243
Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	15,113	12,452	15,113	12,452
Credit Card: | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	10,976	8,166	9,545	8,345
Financing Receivable, Allowance for Credit Loss, Writeoff	(1,925)	(1,047)	(5,481)	(3,011)
Recoveries	333	352	992	1,031
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery	(1,592)	(695)	(4,489)	(1,980)
Provision for credit losses	1,953	1,261	6,298	2,387
Allowance build (release) for credit losses	361	566	1,809	407
Other changes	(13)	(16)	33	(36)
Balance at the end of the period	11,324	8,716	11,324	8,716
Credit Card: | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	0	0	0	0
Provision for credit losses	0	0	0	0
Balance at the end of the period	0	0	0	0
Credit Card: | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	11,324	8,716	11,324	8,716
Consumer Banking: | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	2,185	2,047	2,237	1,918
Financing Receivable, Allowance for Credit Loss, Writeoff	(596)	(410)	(1,653)	(1,090)
Recoveries	247	186	718	584
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery	(349)	(224)	(935)	(506)
Provision for credit losses	213	285	747	696
Allowance build (release) for credit losses	(136)	61	(188)	190
Other changes	0	0	0	0
Balance at the end of the period	2,049	2,108	2,049	2,108
Consumer Banking: | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	0	0	0	0
Provision for credit losses	0	0	0	0
Balance at the end of the period	0	0	0	0
Consumer Banking: | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	2,049	2,108	2,049	2,108
Commercial Portfolio | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1,485	1,278	1,458	1,167
Financing Receivable, Allowance for Credit Loss, Writeoff	(60)	(13)	(462)	(73)
Recoveries	2	1	5	16
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery	(58)	(12)	(457)	(57)
Provision for credit losses	155	119	581	275
Allowance build (release) for credit losses	97	107	124	218
Other changes	0	0	0	0
Balance at the end of the period	1,582	1,385	1,582	1,385
Commercial Portfolio | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	197	239	218	165
Provision for credit losses	(39)	4	(60)	78
Balance at the end of the period	158	243	158	243
Commercial Portfolio | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	$ 1,740	$ 1,628	$ 1,740	$ 1,628