Loans and leases and allowance for credit losses - Summary of Loan grades applied various classes of Commercial and Real Estate Loans (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable Recorded Investment [Line Items]
Year one	$ 19,234	$ 18,423
Year two	15,083	21,683
Year three	17,786	15,025
Year four	11,704	10,555
Year five	8,328	10,062
Prior	28,783	27,464
Total	135,581	134,068
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	34	34
Year two	77	81
Year three	104	47
Year four	56	31
Year five	55	142
Prior	195	190
Total	713	570	$ 303
Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	33,120	29,237
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans	188	40
Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	1,543	1,619
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans Converted to Term Loans	4	5
Residential Real Estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	6	10	12
Residential Real Estate \| Residential
Financing Receivable Recorded Investment [Line Items]
Year one	2,277	1,746
Year two	1,372	4,876
Year three	4,571	3,858
Year four	3,628	2,615
Year five	2,439	1,261
Prior	8,773	8,812
Total	23,166	23,264
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	1
Year four	0	0
Year five	0	3
Prior	6	6
Total	6	10
Residential Real Estate \| Residential \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	106	96
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans	0	0
Residential Real Estate \| Residential \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans Converted to Term Loans	0	0
Residential Real Estate \| Residential \| Current
Financing Receivable Recorded Investment [Line Items]
Year one	2,264	1,726
Year two	1,354	4,709
Year three	4,394	3,732
Year four	3,488	2,543
Year five	2,376	1,215
Prior	7,874	7,885
Total	21,853	21,905
Residential Real Estate \| Residential \| Current \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	103	95
Residential Real Estate \| Residential \| Current \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Residential Real Estate \| Residential \| 30-89 days past due
Financing Receivable Recorded Investment [Line Items]
Year one	12	18
Year two	9	120
Year three	111	88
Year four	77	52
Year five	38	28
Prior	472	488
Total	719	794
Residential Real Estate \| Residential \| 30-89 days past due \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Residential Real Estate \| Residential \| 30-89 days past due \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Residential Real Estate \| Residential \| Accruing Loans Past Due 90 Days or More
Financing Receivable Recorded Investment [Line Items]
Year one	1	1
Year two	7	30
Year three	39	28
Year four	47	17
Year five	20	14
Prior	201	205
Total	315	295
Residential Real Estate \| Residential \| Accruing Loans Past Due 90 Days or More \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Residential Real Estate \| Residential \| Accruing Loans Past Due 90 Days or More \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Residential Real Estate \| Residential \| Nonaccrual
Financing Receivable Recorded Investment [Line Items]
Year one	0	1
Year two	2	17
Year three	27	10
Year four	16	3
Year five	5	4
Prior	226	234
Total	279	270
Residential Real Estate \| Residential \| Nonaccrual \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	3	1
Residential Real Estate \| Residential \| Nonaccrual \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Commercial Portfolio Segment
Financing Receivable Recorded Investment [Line Items]
Year one	9,221	9,010
Year two	6,895	8,434
Year three	6,345	5,133
Year four	3,509	2,465
Year five	1,668	2,332
Prior	5,895	5,474
Revolving Loans	27,815	24,048
Revolving Loans Converted to Term Loans	133	114
Total	61,481	57,010
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	7	10
Year two	33	45
Year three	60	18
Year four	23	13
Year five	30	10
Prior	37	19
Revolving Loans	126	17
Revolving Loans Converted to Term Loans	0	0
Total	316	132
Commercial Portfolio Segment \| Pass
Financing Receivable Recorded Investment [Line Items]
Year one	9,021	8,689
Year two	6,454	8,087
Year three	5,845	4,800
Year four	3,258	2,248
Year five	1,534	2,169
Prior	5,147	4,843
Revolving Loans	26,262	22,345
Revolving Loans Converted to Term Loans	79	70
Total	57,600	53,251
Commercial Portfolio Segment \| Criticized accrual
Financing Receivable Recorded Investment [Line Items]
Year one	189	292
Year two	385	279
Year three	402	277
Year four	210	142
Year five	75	127
Prior	528	481
Revolving Loans	1,359	1,460
Revolving Loans Converted to Term Loans	37	31
Total	3,185	3,089
Commercial Portfolio Segment \| Criticized nonaccrual
Financing Receivable Recorded Investment [Line Items]
Year one	11	29
Year two	56	68
Year three	98	56
Year four	41	75
Year five	59	36
Prior	220	150
Revolving Loans	194	243
Revolving Loans Converted to Term Loans	17	13
Total	696	670
Commercial Real Estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	134	253	60
Commercial Real Estate \| Commercial
Financing Receivable Recorded Investment [Line Items]
Year one	714	2,275
Year two	1,867	2,679
Year three	2,076	1,835
Year four	1,501	2,580
Year five	2,382	4,118
Prior	11,819	11,340
Revolving Loans	421	450
Revolving Loans Converted to Term Loans	0	0
Total	20,780	25,277
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	4	0
Year three	0	0
Year four	1	0
Year five	5	112
Prior	104	129
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	114	241
Commercial Real Estate \| Residential builder and developer
Financing Receivable Recorded Investment [Line Items]
Year one	396	531
Year two	278	270
Year three	74	74
Year four	12	6
Year five	4	61
Prior	11	12
Revolving Loans	60	119
Revolving Loans Converted to Term Loans	0	0
Total	835	1,073
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	3	0
Revolving Loans	0	2
Revolving Loans Converted to Term Loans	0	0
Total	3	2
Commercial Real Estate \| Other commercial construction
Financing Receivable Recorded Investment [Line Items]
Year one	150	866
Year two	1,499	1,771
Year three	1,795	1,051
Year four	648	1,110
Year five	472	1,261
Prior	540	562
Revolving Loans	45	32
Revolving Loans Converted to Term Loans	0	0
Total	5,149	6,653
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	2	0
Year four	0	0
Year five	0	3
Prior	13	7
Revolving Loans	2	0
Revolving Loans Converted to Term Loans	0	0
Total	17	10
Commercial Real Estate \| Pass \| Commercial
Financing Receivable Recorded Investment [Line Items]
Year one	674	2,048
Year two	1,477	1,742
Year three	1,358	1,367
Year four	1,222	2,011
Year five	1,774	3,059
Prior	9,611	8,491
Revolving Loans	413	440
Revolving Loans Converted to Term Loans	0	0
Total	16,529	19,158
Commercial Real Estate \| Pass \| Residential builder and developer
Financing Receivable Recorded Investment [Line Items]
Year one	380	530
Year two	236	252
Year three	40	41
Year four	12	6
Year five	4	2
Prior	10	12
Revolving Loans	60	116
Revolving Loans Converted to Term Loans	0	0
Total	742	959
Commercial Real Estate \| Pass \| Other commercial construction
Financing Receivable Recorded Investment [Line Items]
Year one	108	813
Year two	1,395	1,366
Year three	1,091	651
Year four	269	373
Year five	175	646
Prior	379	187
Revolving Loans	42	30
Revolving Loans Converted to Term Loans	0	0
Total	3,459	4,066
Commercial Real Estate \| Criticized accrual \| Commercial
Financing Receivable Recorded Investment [Line Items]
Year one	39	227
Year two	389	891
Year three	665	465
Year four	253	456
Year five	591	966
Prior	1,839	2,238
Revolving Loans	7	7
Revolving Loans Converted to Term Loans	0	0
Total	3,783	5,250
Commercial Real Estate \| Criticized accrual \| Residential builder and developer
Financing Receivable Recorded Investment [Line Items]
Year one	15	1
Year two	42	18
Year three	34	30
Year four	0	0
Year five	0	59
Prior	0	0
Revolving Loans	0	3
Revolving Loans Converted to Term Loans	0	0
Total	91	111
Commercial Real Estate \| Criticized accrual \| Other commercial construction
Financing Receivable Recorded Investment [Line Items]
Year one	42	53
Year two	104	391
Year three	687	390
Year four	346	691
Year five	297	565
Prior	145	326
Revolving Loans	3	0
Revolving Loans Converted to Term Loans	0	0
Total	1,624	2,416
Commercial Real Estate \| Criticized nonaccrual \| Commercial
Financing Receivable Recorded Investment [Line Items]
Year one	1	0
Year two	1	46
Year three	53	3
Year four	26	113
Year five	17	93
Prior	369	611
Revolving Loans	1	3
Revolving Loans Converted to Term Loans	0	0
Total	468	869
Commercial Real Estate \| Criticized nonaccrual \| Residential builder and developer
Financing Receivable Recorded Investment [Line Items]
Year one	1	0
Year two	0	0
Year three	0	3
Year four	0	0
Year five	0	0
Prior	1	0
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	2	3
Commercial Real Estate \| Criticized nonaccrual \| Other commercial construction
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	14
Year three	17	10
Year four	33	46
Year five	0	50
Prior	16	49
Revolving Loans	0	2
Revolving Loans Converted to Term Loans	0	0
Total	66	171
Consumer:
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	257	175	$ 112
Consumer: \| Home equity lines and loans
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	2
Year four	2	2
Year five	2	13
Prior	95	106
Total	4,592	4,649
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Total	4	6
Consumer: \| Home equity lines and loans \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	3,085	3,025
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans	0	1
Consumer: \| Home equity lines and loans \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	1,408	1,501
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans Converted to Term Loans	4	5
Consumer: \| Home equity lines and loans \| Current
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	2
Year four	2	2
Year five	2	13
Prior	91	98
Total	4,482	4,528
Consumer: \| Home equity lines and loans \| Current \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	3,085	3,022
Consumer: \| Home equity lines and loans \| Current \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	1,302	1,391
Consumer: \| Home equity lines and loans \| 30-89 days past due
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	2	3
Total	29	40
Consumer: \| Home equity lines and loans \| 30-89 days past due \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Consumer: \| Home equity lines and loans \| 30-89 days past due \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	27	37
Consumer: \| Home equity lines and loans \| Accruing Loans Past Due 90 Days or More
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Total	0	0
Consumer: \| Home equity lines and loans \| Accruing Loans Past Due 90 Days or More \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Consumer: \| Home equity lines and loans \| Accruing Loans Past Due 90 Days or More \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Consumer: \| Home equity lines and loans \| Nonaccrual
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	2	5
Total	81	81
Consumer: \| Home equity lines and loans \| Nonaccrual \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	3
Consumer: \| Home equity lines and loans \| Nonaccrual \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	79	73
Consumer: \| Recreational finance
Financing Receivable Recorded Investment [Line Items]
Year one	3,934	2,667
Year two	2,227	2,359
Year three	2,065	1,884
Year four	1,686	1,306
Year five	1,119	797
Prior	1,533	1,045
Total	12,564	10,058
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	8	4
Year two	20	13
Year three	24	14
Year four	20	12
Year five	16	9
Prior	27	16
Total	115	68
Consumer: \| Recreational finance \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans	0	0
Consumer: \| Recreational finance \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving Loans Converted to Term Loans	0	0
Consumer: \| Recreational finance \| Current
Financing Receivable Recorded Investment [Line Items]
Year one	3,918	2,653
Year two	2,203	2,338
Year three	2,044	1,857
Year four	1,661	1,286
Year five	1,100	781
Prior	1,503	1,020
Total	12,429	9,935
Consumer: \| Recreational finance \| Current \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Consumer: \| Recreational finance \| Current \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Consumer: \| Recreational finance \| 30-89 days past due
Financing Receivable Recorded Investment [Line Items]
Year one	13	11
Year two	18	16
Year three	15	19
Year four	20	14
Year five	15	11
Prior	23	16
Total	104	87
Consumer: \| Recreational finance \| 30-89 days past due \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Consumer: \| Recreational finance \| 30-89 days past due \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Consumer: \| Recreational finance \| Accruing Loans Past Due 90 Days or More
Financing Receivable Recorded Investment [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Total	0	0
Consumer: \| Recreational finance \| Accruing Loans Past Due 90 Days or More \| Revolving Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans	0	0
Consumer: \| Recreational finance \| Accruing Loans Past Due 90 Days or More \| Revolving Loans Converted to Term Loans
Financing Receivable Recorded Investment [Line Items]
Revolving Loans Converted to Term Loans	0	0
Consumer: \| Recreational finance \| Nonaccrual
Financing Receivable Recorded Investment [Line Items]

Loans and leases and allowance for credit losses - Summary of Loan grades applied various classes of Commercial and Real Estate Loans (Detail) - USD ($)
$ in Millions