Loans and Allowance for Credit Losses - Summary of Loans by Portfolio Class and Company's Internal Credit Quality Rating (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 318,934	$ 312,028
Total outstanding commitments	686,422	671,419
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	313,734	306,471
Total outstanding commitments	678,366	662,363
Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,313	1,684
Total outstanding commitments	2,372	3,372
Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,887	3,873
Total outstanding commitments	5,684	5,684
Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,200	5,557
Total outstanding commitments	8,056	9,056
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	13,607
Originated in 2021	47,792	51,829
Originated in 2020	12,129	14,528
Originated in 2019	8,884	10,364
Originated in 2018	4,530	5,161
Originated prior to 2018	4,317	5,034
Revolving	26,211	25,107
Total loans	117,470	112,023
Commercial [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	13,554
Originated in 2021	47,131	51,155
Originated in 2020	11,779	14,091
Originated in 2019	8,761	10,159
Originated in 2018	4,475	5,122
Originated prior to 2018	4,251	4,923
Revolving	25,756	24,722
Total loans	115,707	110,172
Commercial [Member] \| Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	8
Originated in 2021	378	387
Originated in 2020	38	304
Originated in 2019	24	151
Originated in 2018	11	3
Originated prior to 2018	17	30
Revolving	261	268
Total loans	737	1,143
Commercial [Member] \| Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	45
Originated in 2021	283	287
Originated in 2020	312	133
Originated in 2019	99	54
Originated in 2018	44	36
Originated prior to 2018	49	81
Revolving	194	117
Total loans	1,026	708
Commercial [Member] \| Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	53
Originated in 2021	661	674
Originated in 2020	350	437
Originated in 2019	123	205
Originated in 2018	55	39
Originated prior to 2018	66	111
Revolving	455	385
Total loans	1,763	1,851
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	3,465
Originated in 2021	13,141	14,360
Originated in 2020	7,226	7,920
Originated in 2019	6,616	7,229
Originated in 2018	3,102	3,254
Originated prior to 2018	4,069	4,752
Revolving	1,572	1,538
Total loans	39,191	39,053
Commercial Real Estate [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	3,170
Originated in 2021	12,419	13,364
Originated in 2020	6,907	7,459
Originated in 2019	5,750	6,368
Originated in 2018	2,847	2,996
Originated prior to 2018	3,898	4,473
Revolving	1,530	1,494
Total loans	36,521	36,154
Commercial Real Estate [Member] \| Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	110
Originated in 2021	17	6
Originated in 2020	78	198
Originated in 2019	310	251
Originated in 2018	42	29
Originated prior to 2018	19	55
Revolving		1
Total loans	576	540
Commercial Real Estate [Member] \| Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	185
Originated in 2021	705	990
Originated in 2020	241	263
Originated in 2019	556	610
Originated in 2018	213	229
Originated prior to 2018	152	224
Revolving	42	43
Total loans	2,094	2,359
Commercial Real Estate [Member] \| Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	295
Originated in 2021	722	996
Originated in 2020	319	461
Originated in 2019	866	861
Originated in 2018	255	258
Originated prior to 2018	171	279
Revolving	42	44
Total loans	2,670	2,899
Residential Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	6,431
Originated in 2021	29,725	29,885
Originated in 2020	14,860	15,957
Originated in 2019	6,177	6,974
Originated in 2018	2,573	2,919
Originated prior to 2018	18,720	20,757
Revolving	1	1
Total loans	78,487	76,493
Residential Mortgages [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	6,431
Originated in 2021	29,721	29,882
Originated in 2020	14,850	15,948
Originated in 2019	6,154	6,938
Originated in 2018	2,553	2,889
Originated prior to 2018	18,407	20,415
Revolving	1	1
Total loans	78,117	76,073
Residential Mortgages [Member] \| Special Mention Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2020		1
Total loans		1
Residential Mortgages [Member] \| Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2021	4	3
Originated in 2020	10	8
Originated in 2019	23	36
Originated in 2018	20	30
Originated prior to 2018	313	342
Total loans	370	419
Residential Mortgages [Member] \| Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2021	4	3
Originated in 2020	10	9
Originated in 2019	23	36
Originated in 2018	20	30
Originated prior to 2018	313	342
Total loans	370	420
Other Retail [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	4,644
Originated in 2021	20,502	22,461
Originated in 2020	10,981	12,080
Originated in 2019	6,341	7,240
Originated in 2018	2,687	3,299
Originated prior to 2018	3,194	3,723
Revolving	12,771	12,644
Revolving converted to term	503	512
Total loans	61,623	61,959
Other Retail [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2022	4,644
Originated in 2021	20,495	22,455
Originated in 2020	10,972	12,071
Originated in 2019	6,327	7,223
Originated in 2018	2,675	3,285
Originated prior to 2018	3,174	3,699
Revolving	12,644	12,532
Revolving converted to term	460	472
Total loans	61,391	61,737
Other Retail [Member] \| Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2021	7	6
Originated in 2020	9	9
Originated in 2019	14	17
Originated in 2018	12	14
Originated prior to 2018	20	24
Revolving	127	112
Revolving converted to term	43	40
Total loans	232	222
Other Retail [Member] \| Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Originated in 2021	7	6
Originated in 2020	9	9
Originated in 2019	14	17
Originated in 2018	12	14
Originated prior to 2018	20	24
Revolving	127	112
Revolving converted to term	43	40
Total loans	232	222
Credit Card [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	22,163	22,500
Credit Card [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	21,998	22,335
Credit Card [Member] \| Classified Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	165	165
Credit Card [Member] \| Total Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 165	$ 165

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