Loans and Allowance for Credit Losses - Summary of the Company's Internal Credit Quality Rating of Loans by Portfolio Class (Detail) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment [Line Items]
Total loans		$ 375,234	$ 388,213
Total outstanding commitments		778,596	780,670
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		364,527	382,382
Total outstanding commitments		765,095	772,804
Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		2,834	1,794
Total outstanding commitments		3,866	2,825
Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	7,873	4,037
Total outstanding commitments	[1]	9,635	5,041
Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		10,707	5,831
Total outstanding commitments		13,501	7,866
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		37,069
Originated in 2022		45,915	61,789
Originated in 2021		10,939	26,648
Originated in 2020		3,680	7,255
Originated in 2019		1,771	4,223
Originated prior to 2019		4,445	9,179
Revolving	[2]	29,500	26,596
Total loans		133,319	135,690
Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		35,634
Originated in 2022		45,120	61,229
Originated in 2021		10,681	26,411
Originated in 2020		3,476	7,049
Originated in 2019		1,653	3,962
Originated prior to 2019		4,293	8,986
Revolving	[2]	28,020	25,888
Total loans		128,877	133,525
Commercial [Member] | Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		725
Originated in 2022		502	245
Originated in 2021		82	159
Originated in 2020		47	68
Originated in 2019		5	51
Originated prior to 2019		42	64
Revolving	[2]	346	344
Total loans		1,749	931
Commercial [Member] | Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[1]	710
Originated in 2022	[1]	293	315
Originated in 2021	[1]	176	78
Originated in 2020	[1]	157	138
Originated in 2019	[1]	113	210
Originated prior to 2019	[1]	110	129
Revolving	[1],[2]	1,134	364
Total loans	[1]	2,693	1,234
Commercial [Member] | Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		1,435
Originated in 2022		795	560
Originated in 2021		258	237
Originated in 2020		204	206
Originated in 2019		118	261
Originated prior to 2019		152	193
Revolving	[2]	1,480	708
Total loans		4,442	2,165
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		9,792
Originated in 2022		14,144	15,252
Originated in 2021		10,640	13,835
Originated in 2020		4,241	6,703
Originated in 2019		5,635	7,546
Originated prior to 2019		7,018	10,652
Revolving		2,661	1,499
Total loans		54,131	55,487
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		7,676
Originated in 2022		12,594	14,527
Originated in 2021		9,951	13,565
Originated in 2020		4,088	6,489
Originated in 2019		5,149	6,991
Originated prior to 2019		6,596	9,639
Revolving		2,627	1,489
Total loans		48,681	52,700
Commercial Real Estate [Member] | Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		367
Originated in 2022		211	206
Originated in 2021		303	171
Originated in 2020		41	97
Originated in 2019		105	251
Originated prior to 2019		53	138
Revolving		3
Total loans		1,083	863
Commercial Real Estate [Member] | Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[1]	1,749
Originated in 2022	[1]	1,339	519
Originated in 2021	[1]	386	99
Originated in 2020	[1]	112	117
Originated in 2019	[1]	381	304
Originated prior to 2019	[1]	369	875
Revolving	[1]	31	10
Total loans	[1]	4,367	1,924
Commercial Real Estate [Member] | Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		2,116
Originated in 2022		1,550	725
Originated in 2021		689	270
Originated in 2020		153	214
Originated in 2019		486	555
Originated prior to 2019		422	1,013
Revolving		34	10
Total loans		5,450	2,787
Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[3]	8,057
Originated in 2022	[3]	29,122	28,452
Originated in 2021	[3]	36,685	39,534
Originated in 2020	[3]	15,005	16,564
Originated in 2019	[3]	5,998	7,240
Originated prior to 2019	[3]	20,188	24,055
Total loans	[3],[4]	115,055	115,845
Residential Mortgages [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[3]	8,056
Originated in 2022	[3]	29,113	28,452
Originated in 2021	[3]	36,675	39,527
Originated in 2020	[3]	14,995	16,556
Originated in 2019	[3]	5,981	7,222
Originated prior to 2019	[3]	19,937	23,658
Total loans	[3]	114,757	115,415
Residential Mortgages [Member] | Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2021	[3]	1
Originated prior to 2019	[3]	1
Total loans	[3]	2
Residential Mortgages [Member] | Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[1],[3]	1
Originated in 2022	[1],[3]	9
Originated in 2021	[1],[3]	9	7
Originated in 2020	[1],[3]	10	8
Originated in 2019	[1],[3]	17	18
Originated prior to 2019	[1],[3]	250	397
Total loans	[1],[3]	296	430
Residential Mortgages [Member] | Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[3]	1
Originated in 2022	[3]	9
Originated in 2021	[3]	10	7
Originated in 2020	[3]	10	8
Originated in 2019	[3]	17	18
Originated prior to 2019	[3]	251	397
Total loans	[3]	298	430
Other Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		4,034
Originated in 2022		5,999	9,569
Originated in 2021		11,288	15,364
Originated in 2020		5,221	7,839
Originated in 2019		2,020	3,431
Originated prior to 2019		2,436	3,720
Revolving		13,846	14,127
Revolving converted to term		805	846
Total loans		45,649	54,896
Other Retail [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		4,033
Originated in 2022		5,990	9,563
Originated in 2021		11,274	15,352
Originated in 2020		5,212	7,828
Originated in 2019		2,012	3,418
Originated prior to 2019		2,422	3,689
Revolving		13,748	14,029
Revolving converted to term		756	800
Total loans		45,447	54,679
Other Retail [Member] | Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023	[1]	1
Originated in 2022	[1]	9	6
Originated in 2021	[1]	14	12
Originated in 2020	[1]	9	11
Originated in 2019	[1]	8	13
Originated prior to 2019	[1]	14	31
Revolving	[1]	98	98
Revolving converted to term	[1]	49	46
Total loans	[1]	202	217
Other Retail [Member] | Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2023		1
Originated in 2022		9	6
Originated in 2021		14	12
Originated in 2020		9	11
Originated in 2019		8	13
Originated prior to 2019		14	31
Revolving		98	98
Revolving converted to term		49	46
Total loans		202	217
Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[5]	27,080	26,295
Credit Card [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[5]	26,765	26,063
Credit Card [Member] | Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1],[5]	315	232
Credit Card [Member] | Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[5]	$ 315	$ 232

[1] Classified rating on consumer loans primarily based on delinquency status.

[2] Includes an immaterial amount of revolving converted to term loans.

[3] At September 30, 2023, $2.0 billion of GNMA loans 90 days or more past due and $963 million of modified GNMA loans whose repayments are insured by the Federal Housing Administration or guaranteed by the United States Department of Veterans Affairs were classified with a pass rating, compared with $2.2 billion and $1.0 billion at December 31, 2022, respectively.

[4] At September 30, 2023, $558 million of loans 30–89 days past due and $2.0 billion of loans 90 days or more past due purchased and that could be purchased from Government National Mortgage Association (“GNMA”) mortgage pools under delinquent loan repurchase options whose repayments are insured by the Federal Housing Administration or guaranteed by the United States Department of Veterans Affairs, were classified as current, compared with $647 million and $2.2 billion at December 31, 2022, respectively.

[5] Predominately all credit card loans are considered revolving loans. Includes an immaterial amount of revolving converted to term loans.