Loans and Allowance for Credit Losses, Troubled Debt Restructurings, Current Defaults (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	$ 73	$ 83	$ 169	$ 235
Total Commercial [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	30	37	84	149
Commercial and industrial loans [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	25	7	48	93
Commercial real estate mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	5	14	33	40
Commercial real estate construction [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	0	16	3	16
Total Consumer [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	43	46	85	86
Real estate 1-4 family first mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	13	15	24	33
Real estate 1-4 family junior lien mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	4	2	9	7
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	21	24	42	37
Automobile [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	4	4	7	7
Other revolving credit and installment [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	$ 1	$ 1	$ 3	$ 2