Asset Quality Asset Quality - Consumer Credit Exposure (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 103,081	$ 94,646
Accrued interest	235	244
Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,552
2019	6,066
2018	1,727
2017	1,190
2016	1,267
Prior	3,616
Revolving Loans Amortized Cost Basis	6,248
Revolving Loans Converted to Term Loans Amortized Cost Basis	934
Total	28,600	26,614
Accrued interest	102
Consumer Loans | Real estate — residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,126
2019	2,160
2018	358
2017	361
2016	737
Prior	1,972
Revolving Loans Amortized Cost Basis	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	8,715	7,023
Consumer Loans | Real estate — residential mortgage | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,561
2019	1,774
2018	242
2017	286
2016	604
Prior	1,372
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	6,839
Consumer Loans | Real estate — residential mortgage | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
2020	550
2019	350
2018	88
2017	58
2016	108
Prior	362
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,516
Consumer Loans | Real estate — residential mortgage | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	15
2019	34
2018	24
2017	11
2016	23
Prior	183
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	290
Consumer Loans | Real estate — residential mortgage | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	2
2018	4
2017	6
2016	2
Prior	55
Revolving Loans Amortized Cost Basis	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	70
Consumer Loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	881
2019	718
2018	311
2017	340
2016	315
Prior	1,352
Revolving Loans Amortized Cost Basis	4,637
Revolving Loans Converted to Term Loans Amortized Cost Basis	934
Total	9,488	10,274
Consumer Loans | Home equity loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	644
2019	417
2018	166
2017	192
2016	185
Prior	815
Revolving Loans Amortized Cost Basis	2,874
Revolving Loans Converted to Term Loans Amortized Cost Basis	639
Total	5,932
Consumer Loans | Home equity loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
2020	213
2019	249
2018	115
2017	119
2016	96
Prior	380
Revolving Loans Amortized Cost Basis	1,308
Revolving Loans Converted to Term Loans Amortized Cost Basis	229
Total	2,709
Consumer Loans | Home equity loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	22
2019	50
2018	29
2017	29
2016	34
Prior	155
Revolving Loans Amortized Cost Basis	450
Revolving Loans Converted to Term Loans Amortized Cost Basis	65
Total	834
Consumer Loans | Home equity loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2
2019	2
2018	1
2017	0
2016	0
Prior	2
Revolving Loans Amortized Cost Basis	5
Revolving Loans Converted to Term Loans Amortized Cost Basis	1
Total	13
Consumer Loans | Consumer direct loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,844
2019	1,380
2018	266
2017	91
2016	52
Prior	122
Revolving Loans Amortized Cost Basis	640
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	4,395	3,513
Consumer Loans | Consumer direct loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,426
2019	1,008
2018	131
2017	39
2016	21
Prior	65
Revolving Loans Amortized Cost Basis	127
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	2,817
Consumer Loans | Consumer direct loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
2020	367
2019	295
2018	91
2017	26
2016	16
Prior	33
Revolving Loans Amortized Cost Basis	263
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,091
Consumer Loans | Consumer direct loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	17
2019	38
2018	22
2017	9
2016	5
Prior	12
Revolving Loans Amortized Cost Basis	86
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	189
Consumer Loans | Consumer direct loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
2020	34
2019	39
2018	22
2017	17
2016	10
Prior	12
Revolving Loans Amortized Cost Basis	164
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	298
Consumer Loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	970
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	970	1,130
Consumer Loans | Credit cards | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	469
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	469
Consumer Loans | Credit cards | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	405
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	405
Consumer Loans | Credit cards | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	95
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	95
Consumer Loans | Credit cards | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1
Consumer Loans | Consumer indirect loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,701
2019	1,808
2018	792
2017	398
2016	163
Prior	170
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	5,032	$ 4,674
Consumer Loans | Consumer indirect loans | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	944
2019	991
2018	415
2017	221
2016	87
Prior	80
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	2,738
Consumer Loans | Consumer indirect loans | FICO Score, 660 to 749
Financing Receivable, Credit Quality Indicator [Line Items]
2020	595
2019	633
2018	264
2017	115
2016	46
Prior	57
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,710
Consumer Loans | Consumer indirect loans | FICO Score, Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	125
2019	184
2018	113
2017	62
2016	30
Prior	33
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	547
Consumer Loans | Consumer indirect loans | FICO Score, No Score
Financing Receivable, Credit Quality Indicator [Line Items]
2020	37
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	$ 37