Loans and Allowance for Credit Losses - Composition of Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 374,588	$ 373,835
Percent of Total	100.00%	100.00%
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 134,726	$ 131,881
Percent of Total	36.00%	35.30%
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 130,530	$ 127,676
Percent of Total	34.80%	34.20%
Commercial | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 4,196	$ 4,205
Percent of Total	1.20%	1.10%
Commercial | Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 52,677	$ 53,455
Percent of Total	14.10%	14.30%
Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 41,157	$ 41,934
Percent of Total	11.00%	11.20%
Commercial | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 11,520	$ 11,521
Percent of Total	3.10%	3.10%
Consumer | Total residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 116,079	$ 115,530
Percent of Total	31.00%	30.90%
Consumer | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 109,396	$ 108,605
Percent of Total	29.20%	29.00%
Consumer | Home equity loans, first liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 6,683	$ 6,925
Percent of Total	1.80%	1.90%
Consumer | Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 27,844	$ 28,560
Percent of Total	7.40%	7.60%
Consumer | Total other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 43,262	$ 44,409
Percent of Total	11.50%	11.90%
Consumer | Retail leasing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 4,137	$ 4,135
Percent of Total	1.10%	1.10%
Consumer | Home equity and second mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 12,932	$ 13,056
Percent of Total	3.50%	3.50%
Consumer | Revolving credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 3,473	$ 3,668
Percent of Total	0.90%	1.00%
Consumer | Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 13,921	$ 13,889
Percent of Total	3.70%	3.70%
Consumer | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 8,799	$ 9,661
Percent of Total	2.30%	2.60%