Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Accrual and Nonaccrual (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable	$ 84,974	$ 88,213
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	3,549
2019	6,807
2018	3,810
2017	6,345
2016	5,770
Prior	7,342
Revolving Loans	1,370
Financing receivable	$ 34,993	$ 42,468
2020 Percentage	10.00%
2019 Percentage	20.00%
2018 Percentage	11.00%
2017 Percentage	18.00%
2016 Percentage	16.00%
Prior Percentage	21.00%
Revolving Percentage	4.00%
Total	100.00%
Consumer | Residential mortgage and home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	$ 1
2019	14
2018	5
2017	8
2016	14
Prior	144
Revolving loans	5
Financing receivable	191
2020	3,007
2019	4,862
2020	3,006
2019	4,848
2018	3,251
2017	6,298
2016	5,750
Prior	7,167
Revolving loans	1,108
Financing receivable	31,428
2018	3,256
2017	6,306
2016	5,764
Prior	7,311
Revolving Loans	1,113
Financing receivable	$ 31,619
2020 Percentage	10.00%
2019 Percentage	15.00%
2018 Percentage	10.00%
2017 Percentage	20.00%
2016 Percentage	18.00%
Prior Percentage	23.00%
Revolving Percentage	4.00%
Total	100.00%
Consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	$ 0
2019	0
2018	0
2017	0
2016	0
Prior	2
Revolving loans	0
Financing receivable	2
2020	542
2019	1,945
2020	542
2019	1,945
2018	554
2017	39
2016	6
Prior	29
Revolving loans	257
Financing receivable	3,372
2018	554
2017	39
2016	6
Prior	31
Revolving Loans	257
Financing receivable	$ 3,374