Loans and Related Allowance for Credit Losses (Home Equity and Residential Real Estate Credit Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 258,236	$ 239,843
Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1,783
Financing receivable, originated in 2019	2,473
Financing receivable, originated in 2018	746
Financing receivable, originated in 2017	1,012
Financing receivable, originated in 2016	844
Prior	4,772
Revolving Loans	9,547
Revolving Loans Converted to Term	3,702
Total Loans	24,879	25,085
Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	3,880
Financing receivable, originated in 2019	5,609
Financing receivable, originated in 2018	1,712
Financing receivable, originated in 2017	2,615
Financing receivable, originated in 2016	2,656
Prior	5,997
Total Loans	22,469	21,821
FICO Score- Greater than 660 [Member] \| Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1,738
Financing receivable, originated in 2019	2,353
Financing receivable, originated in 2018	685
Financing receivable, originated in 2017	949
Financing receivable, originated in 2016	792
Prior	4,287
Revolving Loans	9,085
Revolving Loans Converted to Term	2,832
Total Loans	22,721	22,245
FICO Score- Greater than 660 [Member] \| Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	3,858
Financing receivable, originated in 2019	5,530
Financing receivable, originated in 2018	1,655
Financing receivable, originated in 2017	2,538
Financing receivable, originated in 2016	2,548
Prior	4,704
Total Loans	20,833	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	45
Financing receivable, originated in 2019	120
Financing receivable, originated in 2018	61
Financing receivable, originated in 2017	62
Financing receivable, originated in 2016	51
Prior	475
Revolving Loans	449
Revolving Loans Converted to Term	780
Total Loans	2,043	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	20
Financing receivable, originated in 2019	64
Financing receivable, originated in 2018	36
Financing receivable, originated in 2017	39
Financing receivable, originated in 2016	68
Prior	632
Total Loans	859	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	10
Revolving Loans	13
Revolving Loans Converted to Term	90
Total Loans	115	278
No FICO Score Available [Member] \| Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1
Financing receivable, originated in 2019	5
Financing receivable, originated in 2018	8
Financing receivable, originated in 2017	21
Financing receivable, originated in 2016	14
Prior	149
Total Loans	198	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 2020	1
Financing receivable, originated in 2019	10
Financing receivable, originated in 2018	13
Financing receivable, originated in 2017	17
Financing receivable, originated in 2016	26
Prior	512
Total Loans	579	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	33
Financing receivable, originated in 2018	26
Financing receivable, originated in 2017	24
Financing receivable, originated in 2016	14
Prior	127
Revolving Loans	677
Revolving Loans Converted to Term	365
Total Loans	1,266	1,243
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	19
Financing receivable, originated in 2018	44
Financing receivable, originated in 2017	68
Financing receivable, originated in 2016	52
Prior	226
Total Loans	409	333
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 2020	4
Financing receivable, originated in 2019	77
Financing receivable, originated in 2018	32
Financing receivable, originated in 2017	16
Financing receivable, originated in 2016	12
Prior	82
Revolving Loans	693
Revolving Loans Converted to Term	247
Total Loans	1,163	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	7
Financing receivable, originated in 2019	54
Financing receivable, originated in 2018	57
Financing receivable, originated in 2017	55
Financing receivable, originated in 2016	43
Prior	131
Total Loans	347	340
LTV Less Than 90 Percent [Member] \| Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	1,779
Financing receivable, originated in 2019	2,363
Financing receivable, originated in 2018	688
Financing receivable, originated in 2017	972
Financing receivable, originated in 2016	818
Prior	4,563
Revolving Loans	8,177
Revolving Loans Converted to Term	3,090
Total Loans	22,450	22,068
LTV Less Than 90 Percent [Member] \| Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in 2020	3,872
Financing receivable, originated in 2019	5,526
Financing receivable, originated in 2018	1,598
Financing receivable, originated in 2017	2,475
Financing receivable, originated in 2016	2,535
Prior	5,128
Total Loans	$ 21,134	19,305
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

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