Loans and Allowance for Loan Losses - Aging of Balance of Loans Held for Investment By Class (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Aging of loans
Current	$ 85,735	$ 87,798
30 to 89 Days Past Due	611	283
90 Days or More Past Due	189	132
Total past due	800	415
Loans held for investment	86,535	88,213
Loans 90 days or more past due and still accruing	74	20
Commercial
Aging of loans
Current	48,452	45,610
30 to 89 Days Past Due	341	71
90 Days or More Past Due	93	64
Total past due	434	135
Loans held for investment	48,886	45,745
Loans 90 days or more past due and still accruing	50	3
Commercial | Construction
Aging of loans
Loans held for investment	1,712
Consumer
Aging of loans
Current	37,283	42,188
30 to 89 Days Past Due	270	212
90 Days or More Past Due	96	68
Total past due	366	280
Loans held for investment	37,649	42,468
Loans 90 days or more past due and still accruing	24	17
Residential mortgage and home equity | Consumer Loans
Aging of loans
Current	33,463	37,788
30 to 89 Days Past Due	251	179
90 Days or More Past Due	80	51
Total past due	331	230
Loans held for investment	33,794	38,018
Commercial mortgage | Commercial Loans
Aging of loans
Current	16,487	16,858
30 to 89 Days Past Due	179	34
90 Days or More Past Due	17	3
Total past due	196	37
Loans held for investment	16,683	16,895
Commercial and industrial | Commercial Loans
Aging of loans
Current	30,259	27,241
30 to 89 Days Past Due	155	37
90 Days or More Past Due	76	61
Total past due	231	98
Loans held for investment	30,490	27,339
Construction | Commercial Loans
Aging of loans
Current	1,706	1,511
30 to 89 Days Past Due	7	0
90 Days or More Past Due	0	0
Total past due	7	0
Loans held for investment	1,713	1,511
Other consumer | Consumer Loans
Aging of loans
Current	3,820	4,400
30 to 89 Days Past Due	19	33
90 Days or More Past Due	16	17
Total past due	35	50
Loans held for investment	$ 3,855	$ 4,450