Loans and Allowance for Credit Losses, Troubled Debt Restructurings Modifications by Type (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable, troubled debt restructuring	$ 13,300		$ 14,500
Loans and leases receivable, impaired, commitment to lend	506		$ 489
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	951	$ 854
Financial effects of modifications [Abstract]
Charge-offs	$ 14	$ 50
Weighted average interest rate reduction	12.82%	8.38%
Total Commercial [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 339	$ 518
Financial effects of modifications [Abstract]
Charge-offs	$ 6	$ 44
Weighted average interest rate reduction	0.92%	0.82%
Commercial and industrial loans [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 231	$ 347
Financial effects of modifications [Abstract]
Charge-offs	$ 6	$ 44
Weighted average interest rate reduction	0.89%	0.65%
Commercial real estate mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 104	$ 165
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	0.93%	0.97%
Commercial real estate construction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 1	$ 6
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	0.00%	2.49%
Lease financing [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 3	$ 0
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	0.00%	0.00%
Total Consumer [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 612	$ 336
Loan restructuring, trial modifications, amount	0	2
Financial effects of modifications [Abstract]
Charge-offs	$ 8	$ 6
Weighted average interest rate reduction	14.01%	10.00%
Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 539	$ 190
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	1.87%	1.63%
Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 18	$ 21
Financial effects of modifications [Abstract]
Charge-offs	$ 1	$ 0
Weighted average interest rate reduction	2.41%	2.38%
Credit card [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 32	$ 95
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	18.87%	12.33%
Auto [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 15	$ 14
Financial effects of modifications [Abstract]
Charge-offs	$ 7	$ 6
Weighted average interest rate reduction	3.87%	4.69%
Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 8	$ 14
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	12.20%	8.22%
Primary modification type, Principal [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 0	$ 42
Financial effects of modifications [Abstract]
Charge-offs	0	29
Primary modification type, Principal [Member] | Total Commercial [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	18
Primary modification type, Principal [Member] | Commercial and industrial loans [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	18
Primary modification type, Principal [Member] | Commercial real estate mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Principal [Member] | Commercial real estate construction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Principal [Member] | Lease financing [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Principal [Member] | Total Consumer [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	24
Loan restructuring, trial modifications, amount	0	0
Primary modification type, Principal [Member] | Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	21
Primary modification type, Principal [Member] | Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	1
Primary modification type, Principal [Member] | Credit card [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Principal [Member] | Auto [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	2
Primary modification type, Principal [Member] | Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Interest rate reduction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	57	146
Primary modification type, Interest rate reduction [Member] | Total Commercial [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	5	28
Primary modification type, Interest rate reduction [Member] | Commercial and industrial loans [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	15
Primary modification type, Interest rate reduction [Member] | Commercial real estate mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	4	13
Primary modification type, Interest rate reduction [Member] | Commercial real estate construction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Interest rate reduction [Member] | Lease financing [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Interest rate reduction [Member] | Total Consumer [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	52	118
Loan restructuring, trial modifications, amount	0	0
Primary modification type, Interest rate reduction [Member] | Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	7	3
Primary modification type, Interest rate reduction [Member] | Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	5	6
Primary modification type, Interest rate reduction [Member] | Credit card [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	32	95
Primary modification type, Interest rate reduction [Member] | Auto [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	2
Primary modification type, Interest rate reduction [Member] | Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	7	12
Primary modification type, Other concessions [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	894	666
Primary modification type, Other concessions [Member] | Total Commercial [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	334	472
Primary modification type, Other concessions [Member] | Commercial and industrial loans [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	230	314
Primary modification type, Other concessions [Member] | Commercial real estate mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	100	152
Primary modification type, Other concessions [Member] | Commercial real estate construction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	6
Primary modification type, Other concessions [Member] | Lease financing [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	3	0
Primary modification type, Other concessions [Member] | Total Consumer [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	560	194
Loan restructuring, trial modifications, amount	0	2
Primary modification type, Other concessions [Member] | Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	532	166
Primary modification type, Other concessions [Member] | Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	13	14
Primary modification type, Other concessions [Member] | Credit card [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Primary modification type, Other concessions [Member] | Auto [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	14	10
Primary modification type, Other concessions [Member] | Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	2
Trial modifications [Member] | Total Consumer [Member]
Financial effects of modifications [Abstract]
Charge-offs	$ 0	$ 0
Weighted average interest rate reduction	0.00%	0.00%
Financial effects of modification, Recorded investment related to interest rate reduction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 57	$ 160
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Total Commercial [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	5	28
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Commercial and industrial loans [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	15
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Commercial real estate mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	4	13
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Commercial real estate construction [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Lease financing [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	0	0
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Total Consumer [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	52	132
Loan restructuring, trial modifications, amount	0	0
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	7	17
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	5	6
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Credit card [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	32	95
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Auto [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	1	2
Financial effects of modification, Recorded investment related to interest rate reduction [Member] | Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	7	12
Loans remodified [Member]
Primary Modification Type [Abstract]
Financing receivable, troubled debt restructuring, post modification	$ 256	$ 263