Loans and Related Allowance for Credit Losses (Consumer Real Estate Secured Asset Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 241,928	$ 239,843	$ 226,245
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,434
2019	2,000
2018	590
2017	830
2016	694
Prior	4,000
Revolving Loans	8,794
Revolving Loans Converted to Term	3,746
Total Loans	24,088	25,085
Home equity | FICO Score, Greater Than Or Equal To 780
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,019
2019	1,094
2018	311
2017	525
2016	449
Prior	2,467
Revolving Loans	5,382
Revolving Loans Converted to Term	1,480
Total Loans	13,727
Home equity | FICO Score, 720 to 779
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,028
2019	558
2018	153
2017	181
2016	145
Prior	777
Revolving Loans	2,137
Revolving Loans Converted to Term	941
Total Loans	5,920
Home equity | FICO Score, 660 to 719
Financing Receivable, Credit Quality Indicator [Line Items]
2020	334
2019	273
2018	86
2017	84
2016	66
Prior	402
Revolving Loans	985
Revolving Loans Converted to Term	625
Total Loans	2,855
Home equity | FICO Score, Less Than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	52
2019	74
2018	39
2017	39
2016	33
Prior	345
Revolving Loans	277
Revolving Loans Converted to Term	620
Total Loans	1,479
Home equity | FICO Score- Greater than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		22,245
Home equity | FICO Score- Less than or equal to 660
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		2,019
Home equity | No FICO score available
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
2019	1
2018	1
2017	1
2016	1
Prior	9
Revolving Loans	13
Revolving Loans Converted to Term	80
Total Loans	107	278
Home equity | Purchased Impaired Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		543
Home equity | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8
2019	44
2018	18
2017	15
2016	9
Prior	88
Revolving Loans	580
Revolving Loans Converted to Term	279
Total Loans	1,041
Home equity | Greater than or equal to 80% to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	517
2019	320
2018	59
2017	42
2016	25
Prior	158
Revolving Loans	1,781
Revolving Loans Converted to Term	591
Total Loans	3,493
Home equity | Less than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,909
2019	1,636
2018	513
2017	773
2016	660
Prior	3,754
Revolving Loans	6,433
Revolving Loans Converted to Term	2,876
Total Loans	19,554
Home equity | Greater than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		1,243
Home equity | Greater than or equal to 90% to less than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		1,047
Home equity | Less than 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		22,068
Home equity | No LTV ratio available
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		184
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,996
2019	4,158
2018	1,172
2017	1,942
2016	2,069
Prior	5,223
Total Loans	22,560	21,821
Residential real estate | FICO Score, Greater Than Or Equal To 780
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,425
2019	3,099
2018	814
2017	1,432
2016	1,538
Prior	2,551
Total Loans	14,859
Residential real estate | FICO Score, 720 to 779
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,268
2019	820
2018	220
2017	340
2016	335
Prior	818
Total Loans	4,801
Residential real estate | FICO Score, 660 to 719
Financing Receivable, Credit Quality Indicator [Line Items]
2020	252
2019	161
2018	76
2017	98
2016	92
Prior	475
Total Loans	1,154
Residential real estate | FICO Score, Less Than 660
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40
2019	48
2018	33
2017	31
2016	41
Prior	485
Total Loans	678
Residential real estate | FICO Score- Greater than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		19,341
Residential real estate | FICO Score- Less than or equal to 660
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		569
Residential real estate | No FICO score available
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4
2019	2
2018	2
2017	3
2016	6
Prior	129
Total Loans	146	151
Residential real estate | Purchased Impaired Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		1,176
Residential real estate | Government insured or guaranteed loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7
2019	28
2018	27
2017	38
2016	57
Prior	765
Total Loans	922	584
Residential real estate | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3
2019	52
2018	26
2017	42
2016	41
Prior	160
Total Loans	324
Residential real estate | Greater than or equal to 80% to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	495
2019	422
2018	127
2017	156
2016	124
Prior	307
Total Loans	1,631
Residential real estate | Less than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,491
2019	3,656
2018	992
2017	1,706
2016	1,847
Prior	3,991
Total Loans	$ 19,683
Residential real estate | Greater than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		333
Residential real estate | Greater than or equal to 90% to less than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		340
Residential real estate | Less than 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		19,305
Residential real estate | No LTV ratio available
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		$ 83