Asset Quality - Commerical Credit Exposure (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 106,159	$ 94,646
Accrued interest	225	244
Commercial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	13,839
2019	11,659
2018	8,626
2017	5,486
2016	3,915
Prior	9,160
Revolving Loans Amortized Cost Basis	25,315
Revolving Loans Converted to Term Loans Amortized Cost Basis	205
Total	78,205	68,032
Accrued interest	121
Commercial Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	12,038
2019	6,458
2018	5,196
2017	3,485
2016	2,501
Prior	4,223
Revolving Loans Amortized Cost Basis	24,237
Revolving Loans Converted to Term Loans Amortized Cost Basis	159
Total	58,297	48,295
Commercial Loans | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	12,011
2019	6,386
2018	5,004
2017	3,290
2016	2,393
Prior	3,996
Revolving Loans Amortized Cost Basis	22,395
Revolving Loans Converted to Term Loans Amortized Cost Basis	141
Total	55,616
Commercial Loans | Commercial and industrial | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	24
2019	60
2018	164
2017	164
2016	70
Prior	169
Revolving Loans Amortized Cost Basis	1,608
Revolving Loans Converted to Term Loans Amortized Cost Basis	18
Total	2,277
Commercial Loans | Commercial and industrial | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3
2019	12
2018	28
2017	31
2016	38
Prior	58
Revolving Loans Amortized Cost Basis	234
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	404
Commercial Loans | Commercial mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,087
2019	3,311
2018	1,985
2017	1,108
2016	1,001
Prior	3,871
Revolving Loans Amortized Cost Basis	1,059
Revolving Loans Converted to Term Loans Amortized Cost Basis	43
Total	13,465	13,491
Commercial Loans | Commercial mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,087
2019	3,303
2018	1,955
2017	1,040
2016	963
Prior	3,600
Revolving Loans Amortized Cost Basis	1,039
Revolving Loans Converted to Term Loans Amortized Cost Basis	37
Total	13,024
Commercial Loans | Commercial mortgage | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	8
2018	29
2017	65
2016	34
Prior	193
Revolving Loans Amortized Cost Basis	16
Revolving Loans Converted to Term Loans Amortized Cost Basis	5
Total	350
Commercial Loans | Commercial mortgage | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	1
2017	3
2016	4
Prior	78
Revolving Loans Amortized Cost Basis	4
Revolving Loans Converted to Term Loans Amortized Cost Basis	1
Total	91
Commercial Loans | Real estate — construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	205
2019	607
2018	729
2017	239
2016	92
Prior	25
Revolving Loans Amortized Cost Basis	19
Revolving Loans Converted to Term Loans Amortized Cost Basis	3
Total	1,919	1,558
Commercial Loans | Real estate — construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	205
2019	603
2018	721
2017	239
2016	68
Prior	21
Revolving Loans Amortized Cost Basis	18
Revolving Loans Converted to Term Loans Amortized Cost Basis	3
Total	1,878
Commercial Loans | Real estate — construction | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	4
2018	8
2017	0
2016	24
Prior	3
Revolving Loans Amortized Cost Basis	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	40
Commercial Loans | Real estate — construction | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
Prior	1
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1
Commercial Loans | Commercial lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	509
2019	1,283
2018	716
2017	654
2016	321
Prior	1,041
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	4,524	$ 4,688
Commercial Loans | Commercial lease financing | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	503
2019	1,275
2018	702
2017	640
2016	307
Prior	1,030
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	4,457
Commercial Loans | Commercial lease financing | Criticized (Accruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6
2019	8
2018	12
2017	11
2016	10
Prior	11
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	58
Commercial Loans | Commercial lease financing | Criticized (Nonaccruing)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	2
2017	3
2016	4
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	$ 9