Asset Quality - Consumer Credit Exposure (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 100,730	$ 101,185
Accrued interest	225	241
Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	6,991	10,075
One year prior	8,424	5,436
Two years prior	4,091	1,499
Three years prior	1,098	1,040
Four years prior	736	1,119
Prior	3,454	3,224
Revolving Loans Amortized Cost Basis	5,374	5,953
Revolving Loans Converted to Term Loans Amortized Cost Basis	732	859
Total	30,900	29,205
Accrued interest	97	101
Consumer Loans | Real estate — residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Current	4,642	4,322
One year prior	3,825	1,934
Two years prior	1,326	293
Three years prior	203	319
Four years prior	223	665
Prior	1,912	1,765
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	12,131	9,298
Consumer Loans | Real estate — residential mortgage | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	3,871	3,595
One year prior	3,348	1,620
Two years prior	1,106	194
Three years prior	129	254
Four years prior	173	537
Prior	1,353	1,211
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	9,980	7,411
Consumer Loans | Real estate — residential mortgage | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	743	710
One year prior	462	284
Two years prior	201	76
Three years prior	54	48
Four years prior	37	100
Prior	363	332
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	1,860	1,550
Consumer Loans | Real estate — residential mortgage | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	10	16
One year prior	14	28
Two years prior	17	21
Three years prior	18	10
Four years prior	9	26
Prior	157	170
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	225	271
Consumer Loans | Real estate — residential mortgage | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	18	1
One year prior	1	2
Two years prior	2	2
Three years prior	2	7
Four years prior	4	2
Prior	39	52
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	66	66
Consumer Loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,075	1,457
One year prior	1,276	634
Two years prior	491	269
Three years prior	200	299
Four years prior	230	279
Prior	1,173	1,207
Revolving Loans Amortized Cost Basis	3,870	4,357
Revolving Loans Converted to Term Loans Amortized Cost Basis	732	858
Total	9,047	9,360
Consumer Loans | Home equity loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	799	1,043
One year prior	911	404
Two years prior	321	168
Three years prior	128	202
Four years prior	160	190
Prior	818	839
Revolving Loans Amortized Cost Basis	2,426	2,689
Revolving Loans Converted to Term Loans Amortized Cost Basis	508	590
Total	6,071	6,125
Consumer Loans | Home equity loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	262	385
One year prior	335	198
Two years prior	147	82
Three years prior	56	77
Four years prior	55	69
Prior	247	253
Revolving Loans Amortized Cost Basis	1,087	1,237
Revolving Loans Converted to Term Loans Amortized Cost Basis	172	206
Total	2,361	2,507
Consumer Loans | Home equity loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	14	27
One year prior	28	30
Two years prior	21	18
Three years prior	15	20
Four years prior	15	20
Prior	106	113
Revolving Loans Amortized Cost Basis	353	426
Revolving Loans Converted to Term Loans Amortized Cost Basis	51	61
Total	603	715
Consumer Loans | Home equity loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	2
One year prior	2	2
Two years prior	2	1
Three years prior	1	0
Four years prior	0	0
Prior	2	2
Revolving Loans Amortized Cost Basis	4	5
Revolving Loans Converted to Term Loans Amortized Cost Basis	1	1
Total	12	13
Consumer Loans | Consumer direct loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,159	2,407
One year prior	1,904	1,223
Two years prior	972	237
Three years prior	176	83
Four years prior	55	45
Prior	202	111
Revolving Loans Amortized Cost Basis	581	607
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	1
Total	5,049	4,714
Consumer Loans | Consumer direct loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	867	1,840
One year prior	1,457	883
Two years prior	688	115
Three years prior	90	32
Four years prior	24	16
Prior	120	57
Revolving Loans Amortized Cost Basis	112	119
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,358	3,062
Consumer Loans | Consumer direct loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	251	479
One year prior	383	268
Two years prior	220	80
Three years prior	58	22
Four years prior	15	14
Prior	48	33
Revolving Loans Amortized Cost Basis	224	254
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	1
Total	1,199	1,151
Consumer Loans | Consumer direct loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	10	23
One year prior	20	37
Two years prior	28	21
Three years prior	14	8
Four years prior	4	5
Prior	12	10
Revolving Loans Amortized Cost Basis	64	81
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	152	185
Consumer Loans | Consumer direct loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	31	65
One year prior	44	35
Two years prior	36	21
Three years prior	14	21
Four years prior	12	10
Prior	22	11
Revolving Loans Amortized Cost Basis	181	153
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	340	316
Consumer Loans | Commercial credit card
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	923	989
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	923	989
Consumer Loans | Commercial credit card | FICO Score, 750 and above
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	472	488
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	472	488
Consumer Loans | Commercial credit card | FICO Score, 660 to 749
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	372	407
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	372	407
Consumer Loans | Commercial credit card | FICO Score, Less than 660
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	77	93
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	77	93
Consumer Loans | Commercial credit card | FICO Score, No Score
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	2	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	2	1
Consumer Loans | Consumer indirect loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	115	1,889
One year prior	1,419	1,645
Two years prior	1,302	700
Three years prior	519	339
Four years prior	228	130
Prior	167	141
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,750	4,844
Consumer Loans | Consumer indirect loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	115	1,092
One year prior	821	924
Two years prior	770	369
Three years prior	286	188
Four years prior	130	69
Prior	81	66
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	2,203	2,708
Consumer Loans | Consumer indirect loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	653
One year prior	496	558
Two years prior	416	232
Three years prior	163	97
Four years prior	63	36
Prior	54	47
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	1,192	1,623
Consumer Loans | Consumer indirect loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	143
One year prior	102	163
Two years prior	116	99
Three years prior	70	54
Four years prior	35	25
Prior	32	28
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	355	512
Consumer Loans | Consumer indirect loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	1
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	1
Commercial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	9,070	16,230
One year prior	11,208	10,657
Two years prior	9,235	7,206
Three years prior	6,053	4,635
Four years prior	3,862	3,237
Prior	8,980	7,295
Revolving Loans Amortized Cost Basis	21,229	22,529
Revolving Loans Converted to Term Loans Amortized Cost Basis	193	191
Total	69,830	71,980
Accrued interest	127	140
Commercial Loans | Commercial credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Total	135	127
Commercial Loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Current	6,794	13,174
One year prior	8,310	5,712
Two years prior	4,791	4,285
Three years prior	3,676	2,881
Four years prior	2,339	2,134
Prior	4,258	2,995
Revolving Loans Amortized Cost Basis	20,368	21,585
Revolving Loans Converted to Term Loans Amortized Cost Basis	136	141
Total	50,672	52,907
Commercial Loans | Commercial and Industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	6,763	13,100
One year prior	8,185	5,487
Two years prior	4,542	4,040
Three years prior	3,382	2,617
Four years prior	2,124	1,967
Prior	3,974	2,709
Revolving Loans Amortized Cost Basis	19,061	19,832
Revolving Loans Converted to Term Loans Amortized Cost Basis	104	118
Total	48,135	49,870
Commercial Loans | Commercial and Industrial | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	30	66
One year prior	118	198
Two years prior	232	174
Three years prior	242	236
Four years prior	208	150
Prior	236	279
Revolving Loans Amortized Cost Basis	1,086	1,527
Revolving Loans Converted to Term Loans Amortized Cost Basis	30	22
Total	2,182	2,652
Commercial Loans | Commercial and Industrial | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1	8
One year prior	7	27
Two years prior	17	71
Three years prior	52	28
Four years prior	7	17
Prior	48	7
Revolving Loans Amortized Cost Basis	221	226
Revolving Loans Converted to Term Loans Amortized Cost Basis	2	1
Total	355	385
Commercial Loans | Commercial mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,690	1,603
One year prior	1,440	3,080
Two years prior	2,863	1,822
Three years prior	1,524	1,016
Four years prior	944	839
Prior	3,625	3,370
Revolving Loans Amortized Cost Basis	831	912
Revolving Loans Converted to Term Loans Amortized Cost Basis	48	45
Total	12,965	12,687
Commercial Loans | Commercial mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,678	1,591
One year prior	1,415	2,937
Two years prior	2,703	1,737
Three years prior	1,371	867
Four years prior	786	765
Prior	3,254	3,027
Revolving Loans Amortized Cost Basis	716	885
Revolving Loans Converted to Term Loans Amortized Cost Basis	46	43
Total	11,969	11,852
Commercial Loans | Commercial mortgage | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	12	12
One year prior	25	142
Two years prior	156	81
Three years prior	152	145
Four years prior	142	72
Prior	330	255
Revolving Loans Amortized Cost Basis	111	22
Revolving Loans Converted to Term Loans Amortized Cost Basis	2	2
Total	930	731
Commercial Loans | Commercial mortgage | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	0	1
Two years prior	4	4
Three years prior	1	4
Four years prior	16	2
Prior	41	88
Revolving Loans Amortized Cost Basis	4	5
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	66	104
Commercial Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current	177	367
One year prior	559	778
Two years prior	714	548
Three years prior	419	206
Four years prior	174	27
Prior	50	24
Revolving Loans Amortized Cost Basis	30	32
Revolving Loans Converted to Term Loans Amortized Cost Basis	9	5
Total	2,132	1,987
Commercial Loans | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	177	367
One year prior	555	764
Two years prior	700	510
Three years prior	365	188
Four years prior	152	27
Prior	36	22
Revolving Loans Amortized Cost Basis	28	31
Revolving Loans Converted to Term Loans Amortized Cost Basis	9	5
Total	2,022	1,914
Commercial Loans | Construction | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	4	14
Two years prior	14	38
Three years prior	54	18
Four years prior	22	0
Prior	14	2
Revolving Loans Amortized Cost Basis	2	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	110	73
Commercial Loans | 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
Commercial Loans | Commercial lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Current	409	1,086
One year prior	899	1,087
Two years prior	867	551
Three years prior	434	532
Four years prior	405	237
Prior	1,047	906
Revolving Loans Amortized Cost Basis		0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	4,061	4,399
Commercial Loans | Commercial lease financing | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current	409	1,076
One year prior	880	1,050
Two years prior	825	534
Three years prior	416	504
Four years prior	380	228
Prior	1,037	901
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,947	4,293
Commercial Loans | Commercial lease financing | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	10
One year prior	19	35
Two years prior	40	15
Three years prior	17	26
Four years prior	23	7
Prior	8	4
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	107	97
Commercial Loans | Commercial lease financing | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
Current	0	0
One year prior	0	2
Two years prior	2	2
Three years prior	1	2
Four years prior	2	2
Prior	2	1
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	$ 7	$ 9