Loans - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Allowance for loan losses
Beginning balance	$ 4,562	$ 3,271	$ 3,573	$ 3,874
Net (charge-offs)/recoveries	(172)	(76)	(475)	(202)
Provision	481	164	1,777	(281)
Other	(25)	(27)	(29)	(59)
Ending balance	$ 4,846	$ 3,332	$ 4,846	$ 3,332
Allowance ratio	2.90%	2.60%	2.90%	2.60%
Net charge-off ratio	0.40%	0.20%	0.40%	0.20%
Allowance for losses on lending commitments
Beginning balance	$ 705	$ 822	$ 776	$ 557
Provision	34	11	(34)	294
Other			(3)	(18)
Ending balance	739	833	739	833
Wholesale
Allowance for loan losses
Beginning balance	2,458	2,173	2,135	2,584
Net (charge-offs)/recoveries	(43)	(40)	(189)	(49)
Provision	78	25	551	(345)
Other	(25)	(27)	(29)	(59)
Ending balance	$ 2,468	$ 2,131	$ 2,468	$ 2,131
Allowance ratio	1.70%	1.80%	1.70%	1.80%
Net charge-off ratio	0.10%	0.10%	0.20%	0.10%
Allowance for losses on lending commitments
Beginning balance	$ 702	$ 636	$ 589	$ 557
Provision	(10)	13	106	110
Other			(3)	(18)
Ending balance	692	649	692	649
Consumer
Allowance for loan losses
Beginning balance	2,104	1,098	1,438	1,290
Net (charge-offs)/recoveries	(129)	(36)	(286)	(153)
Provision	403	139	1,226	64
Other	0	0	0	0
Ending balance	$ 2,378	$ 1,201	$ 2,378	$ 1,201
Allowance ratio	12.60%	12.40%	12.60%	12.40%
Net charge-off ratio	2.90%	1.60%	2.50%	2.40%
Allowance for losses on lending commitments
Beginning balance	$ 3	$ 186	$ 187	$ 0
Provision	44	(2)	(140)	184
Other			0	0
Ending balance	$ 47	$ 184	$ 47	$ 184