Asset Quality - Consumer Credit Exposure (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 101,185	$ 94,646
Consumer Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	10,075
2019	5,436
2018	1,499
2017	1,040
2016	1,119
Prior	3,224
Revolving Loans Amortized Cost Basis	5,953
Revolving Loans Converted to Term Loans Amortized Cost Basis	859
Total	29,205	26,614
Accrued interest	101
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,322
2019	1,934
2018	293
2017	319
2016	665
Prior	1,765
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	9,298	7,023
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member] | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,595
2019	1,620
2018	194
2017	254
2016	537
Prior	1,211
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	7,411
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	710
2019	284
2018	76
2017	48
2016	100
Prior	332
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,550
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	16
2019	28
2018	21
2017	10
2016	26
Prior	170
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	271
Consumer Loans [Member] | Real Estate - Residential Mortgage [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
2019	2
2018	2
2017	7
2016	2
Prior	52
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	66
Consumer Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,457
2019	634
2018	269
2017	299
2016	279
Prior	1,207
Revolving Loans Amortized Cost Basis	4,357
Revolving Loans Converted to Term Loans Amortized Cost Basis	858
Total	9,360	10,274
Consumer Loans [Member] | Home Equity Loan [Member] | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,043
2019	404
2018	168
2017	202
2016	190
Prior	839
Revolving Loans Amortized Cost Basis	2,689
Revolving Loans Converted to Term Loans Amortized Cost Basis	590
Total	6,125
Consumer Loans [Member] | Home Equity Loan [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	385
2019	198
2018	82
2017	77
2016	69
Prior	253
Revolving Loans Amortized Cost Basis	1,237
Revolving Loans Converted to Term Loans Amortized Cost Basis	206
Total	2,507
Consumer Loans [Member] | Home Equity Loan [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	27
2019	30
2018	18
2017	20
2016	20
Prior	113
Revolving Loans Amortized Cost Basis	426
Revolving Loans Converted to Term Loans Amortized Cost Basis	61
Total	715
Consumer Loans [Member] | Home Equity Loan [Member] | FICO Score, No Score [Member]
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 [Member] | Consumer Direct Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,407
2019	1,223
2018	237
2017	83
2016	45
Prior	111
Revolving Loans Amortized Cost Basis	607
Revolving Loans Converted to Term Loans Amortized Cost Basis	1
Total	4,714	3,513
Consumer Loans [Member] | Consumer Direct Loans [Member] | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,840
2019	883
2018	115
2017	32
2016	16
Prior	57
Revolving Loans Amortized Cost Basis	119
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	3,062
Consumer Loans [Member] | Consumer Direct Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	479
2019	268
2018	80
2017	22
2016	14
Prior	33
Revolving Loans Amortized Cost Basis	254
Revolving Loans Converted to Term Loans Amortized Cost Basis	1
Total	1,151
Consumer Loans [Member] | Consumer Direct Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	23
2019	37
2018	21
2017	8
2016	5
Prior	10
Revolving Loans Amortized Cost Basis	81
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	185
Consumer Loans [Member] | Consumer Direct Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	65
2019	35
2018	21
2017	21
2016	10
Prior	11
Revolving Loans Amortized Cost Basis	153
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	316
Consumer Loans [Member] | Credit Card Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	989
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	989	1,130
Consumer Loans [Member] | Credit Card Receivable [Member] | 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	488
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	488
Consumer Loans [Member] | Credit Card Receivable [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	407
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	407
Consumer Loans [Member] | Credit Card Receivable [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	93
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	93
Consumer Loans [Member] | Credit Card Receivable [Member] | FICO Score, No Score [Member]
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 [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,889
2019	1,645
2018	700
2017	339
2016	130
Prior	141
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	4,844	$ 4,674
Consumer Loans [Member] | Consumer Indirect Loans [Member] | FICO Score, 750 and above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,092
2019	924
2018	369
2017	188
2016	69
Prior	66
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	2,708
Consumer Loans [Member] | Consumer Indirect Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	653
2019	558
2018	232
2017	97
2016	36
Prior	47
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	1,623
Consumer Loans [Member] | Consumer Indirect Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	143
2019	163
2018	99
2017	54
2016	25
Prior	28
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0
Total	512
Consumer Loans [Member] | Consumer Indirect Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
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	$ 1