Asset Quality - Schedule of Commercial Credit Exposure (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 109,885	$ 112,606
Accrued interest	508	522
Total commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,318	6,150
Writeoff, current period	0	1
One year prior	5,917	16,998
Writeoff, one year period	4	8
Two years prior	16,198	11,508
Writeoff, two year period	10	36
Three years prior	10,603	4,178
Writeoff, three year period	24	19
Four years prior	3,916	4,375
Writeoff, four year period	0	13
Prior	11,259	7,448
Writeoff, prior	5	42
Revolving Loans Amortized Cost Basis	26,241	26,721
Writeoff, Revolving Loans Amortized Cost Basis	24	108
Revolving Loans Converted to Term Loans Amortized Cost Basis	199	213
Revolving Loans Converted to Term Loans Amortized Cost Basis, writeoff	0	0
Total	75,651	77,591
Writeoff, total	67	227
Accrued interest	368	383
Total commercial loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,170	4,118
Writeoff, current period	0	1
One year prior	3,962	10,555
Writeoff, one year period	4	7
Two years prior	9,890	6,618
Writeoff, two year period	10	35
Three years prior	5,993	2,774
Writeoff, three year period	24	8
Four years prior	2,635	2,219
Writeoff, four year period	0	11
Prior	5,752	3,774
Writeoff, prior	1	21
Revolving Loans Amortized Cost Basis	25,245	25,619
Writeoff, Revolving Loans Amortized Cost Basis	23	105
Revolving Loans Converted to Term Loans Amortized Cost Basis	146	138
Revolving Loans Converted to Term Loans Amortized Cost Basis, writeoff	0	0
Total	54,793	55,815
Writeoff, total	62	188
Total commercial loans | Commercial and Industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,131	4,020
One year prior	3,722	10,145
Two years prior	9,183	6,141
Three years prior	5,411	2,539
Four years prior	2,329	2,064
Prior	5,282	3,534
Revolving Loans Amortized Cost Basis	23,724	24,395
Revolving Loans Converted to Term Loans Amortized Cost Basis	127	123
Total	50,909	52,961
Total commercial loans | Commercial and Industrial | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	39	84
One year prior	221	361
Two years prior	639	427
Three years prior	517	233
Four years prior	304	127
Prior	376	170
Revolving Loans Amortized Cost Basis	1,409	1,140
Revolving Loans Converted to Term Loans Amortized Cost Basis	19	15
Total	3,524	2,557
Total commercial loans | Commercial and Industrial | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	14
One year prior	19	49
Two years prior	68	50
Three years prior	65	2
Four years prior	2	28
Prior	94	70
Revolving Loans Amortized Cost Basis	112	84
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	360	297
Total commercial loans | Real estate — commercial mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Current	88	1,090
Writeoff, current period	0	0
One year prior	857	4,310
Writeoff, one year period	0	1
Two years prior	4,269	3,334
Writeoff, two year period	0	1
Three years prior	3,234	822
Writeoff, three year period	0	11
Four years prior	784	1,738
Writeoff, four year period	0	2
Prior	4,283	2,755
Writeoff, prior	4	21
Revolving Loans Amortized Cost Basis	974	1,071
Writeoff, Revolving Loans Amortized Cost Basis	1	3
Revolving Loans Converted to Term Loans Amortized Cost Basis	51	67
Revolving Loans Converted to Term Loans Amortized Cost Basis, writeoff	0	0
Total	14,540	15,187
Writeoff, total	5	39
Total commercial loans | Real estate — commercial mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	85	1,084
One year prior	792	3,664
Two years prior	3,470	2,922
Three years prior	2,729	804
Four years prior	711	1,545
Prior	3,715	2,507
Revolving Loans Amortized Cost Basis	927	1,017
Revolving Loans Converted to Term Loans Amortized Cost Basis	48	66
Total	12,477	13,609
Total commercial loans | Real estate — commercial mortgage | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	3	6
One year prior	65	646
Two years prior	796	411
Three years prior	476	15
Four years prior	70	186
Prior	521	193
Revolving Loans Amortized Cost Basis	16	20
Revolving Loans Converted to Term Loans Amortized Cost Basis	3	1
Total	1,950	1,478
Total commercial loans | Real estate — commercial mortgage | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	0	0
Two years prior	3	1
Three years prior	29	3
Four years prior	3	7
Prior	47	55
Revolving Loans Amortized Cost Basis	31	34
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	113	100
Total commercial loans | Real estate — construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current	8	411
Writeoff, current period	0	0
One year prior	518	1,225
Writeoff, one year period	0	0
Two years prior	1,243	972
Writeoff, two year period	0	0
Three years prior	877	221
Writeoff, three year period	0	0
Four years prior	166	103
Writeoff, four year period	0	0
Prior	177	95
Writeoff, prior	0	0
Revolving Loans Amortized Cost Basis	22	31
Writeoff, Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	2	8
Revolving Loans Converted to Term Loans Amortized Cost Basis, writeoff	0	0
Total	3,013	3,066
Writeoff, total	0	0
Total commercial loans | Real estate — construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	8	401
One year prior	508	1,185
Two years prior	1,156	912
Three years prior	812	157
Four years prior	93	62
Prior	103	48
Revolving Loans Amortized Cost Basis	22	31
Revolving Loans Converted to Term Loans Amortized Cost Basis	2	8
Total	2,704	2,804
Total commercial loans | Real estate — construction | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	10
One year prior	10	40
Two years prior	87	60
Three years prior	65	64
Four years prior	73	41
Prior	74	47
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	309	262
Total commercial loans | Real estate — construction | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	0	0
Two years prior	0	0
Three years prior	0	0
Four years prior	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Total commercial loans | Commercial lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Current	52	531
Writeoff, current period	0	0
One year prior	580	908
Writeoff, one year period	0	0
Two years prior	796	584
Writeoff, two year period	0	0
Three years prior	499	361
Writeoff, three year period	0	0
Four years prior	331	315
Writeoff, four year period	0	0
Prior	1,047	824
Writeoff, prior	0	0
Revolving Loans Amortized Cost Basis		0
Writeoff, Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis, writeoff	0	0
Total	3,305	3,523
Writeoff, total	0	0
Total commercial loans | Commercial lease financing | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	52	520
One year prior	550	878
Two years prior	749	575
Three years prior	491	352
Four years prior	318	307
Prior	1,027	808
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,187	3,440
Total commercial loans | Commercial lease financing | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	11
One year prior	30	30
Two years prior	47	9
Three years prior	8	9
Four years prior	13	8
Prior	19	16
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	117	83
Total commercial loans | Commercial lease financing | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	0	0
Two years prior	0	0
Three years prior	0	0
Four years prior	0	0
Prior	1	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	$ 1	$ 0