Loans (Consumer Real Estate Secured Asset Quality Indicators) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 264,643	$ 239,843
Financing receivable, originated in 2020, % of total loans	4.60%
Financing receivable, originated in 2019, % of total loans	14.90%
Financing receivable, originated in 2018, % of total loans	9.80%
Financing receivable, originated in 2017, % of total loans	7.20%
Financing receivable, originated in 2016, % of total loans	5.20%
Prior, % of total loans	12.80%
Revolving Loans, % of total loans	45.50%
Revolving Loans Converted To Term, % of total loans	0.00%
Total Loans, % of total loans	100.00%
Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	$ 785
Financing receivable, originated in 2019	2,647
Financing receivable, originated in 2018	825
Financing receivable, originated in 2017	1,091
Financing receivable, originated in 2016	908
Prior	5,111
Revolving Loans	9,908
Revolving Loans Converted to Term	3,806
Total Loans	$ 25,081	25,085
Financing receivable, originated in 2020, % of total loans	3.10%
Financing receivable, originated in 2019, % of total loans	10.60%
Financing receivable, originated in 2018, % of total loans	3.30%
Financing receivable, originated in 2017, % of total loans	4.30%
Financing receivable, originated in 2016, % of total loans	3.60%
Prior, % of total loans	20.40%
Revolving Loans, % of total loans	39.50%
Revolving Loans Converted To Term, % of total loans	15.20%
Total Loans, % of total loans	100.00%
Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	$ 1,761
Financing receivable, originated in 2019	6,275
Financing receivable, originated in 2018	1,999
Financing receivable, originated in 2017	2,907
Financing receivable, originated in 2016	2,840
Prior	6,468
Total Loans	$ 22,250	21,821
Financing receivable, originated in 2020, % of total loans	7.90%
Financing receivable, originated in 2019, % of total loans	28.10%
Financing receivable, originated in 2018, % of total loans	9.00%
Financing receivable, originated in 2017, % of total loans	13.10%
Financing receivable, originated in 2016, % of total loans	12.80%
Prior, % of total loans	29.10%
Total Loans, % of total loans	100.00%
FICO Score- Greater than 660 [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	$ 773
Financing receivable, originated in 2019	2,521
Financing receivable, originated in 2018	761
Financing receivable, originated in 2017	1,026
Financing receivable, originated in 2016	856
Prior	4,609
Revolving Loans	9,339
Revolving Loans Converted to Term	2,871
Total Loans	22,756	22,245
FICO Score- Greater than 660 [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1,757
Financing receivable, originated in 2019	6,198
Financing receivable, originated in 2018	1,945
Financing receivable, originated in 2017	2,844
Financing receivable, originated in 2016	2,732
Prior	5,166
Total Loans	20,642	19,341
FICO Score- Less than or equal to 660 [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	12
Financing receivable, originated in 2019	126
Financing receivable, originated in 2018	64
Financing receivable, originated in 2017	64
Financing receivable, originated in 2016	51
Prior	493
Revolving Loans	555
Revolving Loans Converted to Term	842
Total Loans	2,207	2,019
FICO Score- Less than or equal to 660 [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	2
Financing receivable, originated in 2019	65
Financing receivable, originated in 2018	41
Financing receivable, originated in 2017	41
Financing receivable, originated in 2016	79
Prior	693
Total Loans	921	569
No FICO Score Available [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2017	1
Financing receivable, originated in 2016	1
Prior	9
Revolving Loans	14
Revolving Loans Converted to Term	93
Total Loans	118	278
No FICO Score Available [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	2
Financing receivable, originated in 2019	3
Financing receivable, originated in 2017	5
Financing receivable, originated in 2016	4
Prior	93
Total Loans	107	151
Purchased Impaired Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		543
Purchased Impaired Loans [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		1,176
Loans Insured or Guaranteed by US Government Authorities [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2019	9
Financing receivable, originated in 2018	13
Financing receivable, originated in 2017	17
Financing receivable, originated in 2016	25
Prior	516
Total Loans	580	584
LTV Greater Than Or Equal To 100 Percent [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2019	18
Financing receivable, originated in 2018	27
Financing receivable, originated in 2017	30
Financing receivable, originated in 2016	18
Prior	144
Revolving Loans	722
Revolving Loans Converted to Term	389
Total Loans	1,348
LTV Greater Than Or Equal To 100 Percent [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2019	3
Financing receivable, originated in 2018	58
Financing receivable, originated in 2017	74
Financing receivable, originated in 2016	68
Prior	241
Total Loans	444
LTV Greater Than Or Equal To 90 Percent To Less Than 100 Percent [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2019	45
Financing receivable, originated in 2018	37
Financing receivable, originated in 2017	20
Financing receivable, originated in 2016	15
Prior	87
Revolving Loans	684
Revolving Loans Converted to Term	263
Total Loans	1,151	1,047
LTV Greater Than Or Equal To 90 Percent To Less Than 100 Percent [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	4
Financing receivable, originated in 2019	27
Financing receivable, originated in 2018	61
Financing receivable, originated in 2017	64
Financing receivable, originated in 2016	50
Prior	155
Total Loans	361	340
LTV Less Than 90 Percent [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	785
Financing receivable, originated in 2019	2,584
Financing receivable, originated in 2018	761
Financing receivable, originated in 2017	1,041
Financing receivable, originated in 2016	875
Prior	4,880
Revolving Loans	8,502
Revolving Loans Converted to Term	3,154
Total Loans	22,582	22,068
LTV Less Than 90 Percent [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1,757
Financing receivable, originated in 2019	6,236
Financing receivable, originated in 2018	1,867
Financing receivable, originated in 2017	2,752
Financing receivable, originated in 2016	2,697
Prior	5,556
Total Loans	$ 20,865	19,305
Ltv Greater Than Or Equal To1 25 Percent [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		366
Ltv Greater Than Or Equal To1 25 Percent [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		112
Ltv Greater Than Or Equal To 100 Percent To Less Than 125 Percent [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		877
Ltv Greater Than Or Equal To 100 Percent To Less Than 125 Percent [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		221
No LTV Ratio Available [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		184
No LTV Ratio Available [Member] | Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		$ 83