Loans and Allowance for Credit Losses, 90 Days or More Past Due and Still Accruing (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Non-PCI [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	$ 7,258	$ 8,704
Non-PCI [Member] | Not government insured/guaranteed [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	780	979
Non-PCI [Member] | Not government insured/guaranteed [Member] | Total Commercial [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	41	94
Non-PCI [Member] | Not government insured/guaranteed [Member] | Commercial and industrial loans [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	17	43
Non-PCI [Member] | Not government insured/guaranteed [Member] | Commercial real estate mortgage [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	24	51
Non-PCI [Member] | Not government insured/guaranteed [Member] | Commercial real estate construction [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	0	0
Non-PCI [Member] | Not government insured/guaranteed [Member] | Total Consumer [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	739	885
Non-PCI [Member] | Not government insured/guaranteed [Member] | Real estate 1-4 family first mortgage [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	108	124
Non-PCI [Member] | Not government insured/guaranteed [Member] | Real estate 1-4 family junior lien mortgage [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	27	32
Non-PCI [Member] | Not government insured/guaranteed [Member] | Credit Card [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	449	513
Non-PCI [Member] | Not government insured/guaranteed [Member] | Automobile [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	63	114
Non-PCI [Member] | Not government insured/guaranteed [Member] | Other revolving credit and installment [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	92	102
Non-PCI [Member] | Government insured/guaranteed [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	6,478	7,725
PCI [Member]
Loans 90 days or more past due and still accruing:
90 days or more past due and still accruing	$ 156	$ 370