Asset Quality - Consumer Credit Exposure (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 98,609	$ 101,185
Accrued interest	211	241
Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	10,467	10,075
One year prior	6,466	5,436
Two years prior	2,429	1,499
Three years prior	501	1,040
Four years prior	432	1,119
Prior	3,081	3,224
Revolving Loans Amortized Cost Basis	5,235	5,953
Revolving Loans Converted to Term Loans Amortized Cost Basis	669	859
Total	29,280	29,205
Accrued interest	95	101
Consumer Loans | Real estate — residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Current	7,413	4,322
One year prior	3,570	1,934
Two years prior	1,139	293
Three years prior	169	319
Four years prior	186	665
Prior	1,726	1,765
Revolving Loans Amortized Cost Basis	1	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	14,204	9,298
Consumer Loans | Real estate — residential mortgage | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	6,071	3,595
One year prior	3,150	1,620
Two years prior	933	194
Three years prior	104	254
Four years prior	141	537
Prior	1,218	1,211
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	11,617	7,411
Consumer Loans | Real estate — residential mortgage | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,300	710
One year prior	407	284
Two years prior	186	76
Three years prior	47	48
Four years prior	31	100
Prior	323	332
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	2,294	1,550
Consumer Loans | Real estate — residential mortgage | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	23	16
One year prior	12	28
Two years prior	19	21
Three years prior	16	10
Four years prior	10	26
Prior	151	170
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	231	271
Consumer Loans | Real estate — residential mortgage | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	19	1
One year prior	1	2
Two years prior	1	2
Three years prior	2	7
Four years prior	4	2
Prior	34	52
Revolving Loans Amortized Cost Basis	1	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	62	66
Consumer Loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,284	1,457
One year prior	1,208	634
Two years prior	435	269
Three years prior	177	299
Four years prior	201	279
Prior	1,062	1,207
Revolving Loans Amortized Cost Basis	3,711	4,357
Revolving Loans Converted to Term Loans Amortized Cost Basis	669	858
Total	8,747	9,360
Consumer Loans | Home equity loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	919	1,043
One year prior	885	404
Two years prior	285	168
Three years prior	113	202
Four years prior	139	190
Prior	739	839
Revolving Loans Amortized Cost Basis	2,333	2,689
Revolving Loans Converted to Term Loans Amortized Cost Basis	462	590
Total	5,875	6,125
Consumer Loans | Home equity loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	345	385
One year prior	295	198
Two years prior	130	82
Three years prior	49	77
Four years prior	47	69
Prior	222	253
Revolving Loans Amortized Cost Basis	1,037	1,237
Revolving Loans Converted to Term Loans Amortized Cost Basis	158	206
Total	2,283	2,507
Consumer Loans | Home equity loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	20	27
One year prior	26	30
Two years prior	20	18
Three years prior	14	20
Four years prior	15	20
Prior	99	113
Revolving Loans Amortized Cost Basis	336	426
Revolving Loans Converted to Term Loans Amortized Cost Basis	48	61
Total	578	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	0	1
Three years prior	1	0
Four years prior	0	0
Prior	2	2
Revolving Loans Amortized Cost Basis	5	5
Revolving Loans Converted to Term Loans Amortized Cost Basis	1	1
Total	11	13
Consumer Loans | Consumer direct loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,766	2,407
One year prior	1,688	1,223
Two years prior	855	237
Three years prior	155	83
Four years prior	45	45
Prior	220	111
Revolving Loans Amortized Cost Basis	595	607
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	1
Total	5,324	4,714
Consumer Loans | Consumer direct loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,287	1,840
One year prior	1,271	883
Two years prior	594	115
Three years prior	76	32
Four years prior	20	16
Prior	137	57
Revolving Loans Amortized Cost Basis	109	119
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,494	3,062
Consumer Loans | Consumer direct loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
Current	413	479
One year prior	350	268
Two years prior	200	80
Three years prior	51	22
Four years prior	13	14
Prior	48	33
Revolving Loans Amortized Cost Basis	217	254
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	1
Total	1,292	1,151
Consumer Loans | Consumer direct loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Current	19	23
One year prior	22	37
Two years prior	29	21
Three years prior	12	8
Four years prior	3	5
Prior	14	10
Revolving Loans Amortized Cost Basis	61	81
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	160	185
Consumer Loans | Consumer direct loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
Current	47	65
One year prior	45	35
Two years prior	32	21
Three years prior	16	21
Four years prior	9	10
Prior	21	11
Revolving Loans Amortized Cost Basis	208	153
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	378	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	928	989
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	928	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	375	407
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	375	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	72	93
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	72	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	9	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	9	1
Consumer Loans | Consumer indirect loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current	4	1,889
One year prior	0	1,645
Two years prior	0	700
Three years prior	0	339
Four years prior	0	130
Prior	73	141
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	77	4,844
Consumer Loans | Consumer indirect loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
Current	4	1,092
One year prior	0	924
Two years prior	0	369
Three years prior	0	188
Four years prior	0	69
Prior	36	66
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	40	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	0	558
Two years prior	0	232
Three years prior	0	97
Four years prior	0	36
Prior	26	47
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	26	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	0	163
Two years prior	0	99
Three years prior	0	54
Four years prior	0	25
Prior	11	28
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	11	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