Loans and Related Allowance for Credit Losses, Troubled Debt Restructurings, Current Defaults (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	$ 247	$ 96
Total Commercial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	206	54
Commercial and industrial loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	185	23
Commercial real estate mortgage [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	21	28
Commercial real estate construction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	0	3
Total Consumer [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	41	42
Real estate 1-4 family first mortgage [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	10	11
Real estate 1-4 family junior lien mortgage [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	2	5
Credit card [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	26	21
Automobile [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	2	3
Other revolving credit and installment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment of defaults	$ 1	$ 2