Loans and Allowance for Credit Losses - Composition of Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 381,819	$ 379,832
Percent of Total	100.00%	100.00%
Commercial | Total commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 144,081	$ 139,484
Percent of Total	37.70%	36.70%
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 139,840	$ 135,254
Percent of Total	36.60%	35.60%
Commercial | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 4,241	$ 4,230
Percent of Total	1.10%	1.10%
Commercial | Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 48,334	$ 48,859
Percent of Total	12.70%	12.90%
Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 38,064	$ 38,619
Percent of Total	10.00%	10.20%
Commercial | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 10,270	$ 10,240
Percent of Total	2.70%	2.70%
Consumer | Total residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 118,907	$ 118,813
Percent of Total	31.10%	31.30%
Consumer | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 113,112	$ 112,806
Percent of Total	29.60%	29.70%
Consumer | Home equity loans, first liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 5,795	$ 6,007
Percent of Total	1.50%	1.60%
Consumer | Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 29,223	$ 30,350
Percent of Total	7.70%	8.00%
Consumer | Total other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 41,274	$ 42,326
Percent of Total	10.80%	11.10%
Consumer | Retail leasing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 3,928	$ 4,040
Percent of Total	1.00%	1.00%
Consumer | Home equity and second mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 13,540	$ 13,565
Percent of Total	3.60%	3.60%
Consumer | Revolving credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 3,791	$ 3,747
Percent of Total	1.00%	1.00%
Consumer | Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 14,190	$ 14,373
Percent of Total	3.70%	3.80%
Consumer | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 5,825	$ 6,601
Percent of Total	1.50%	1.70%