Loans and Allowance for Credit Losses - Composition of Loan Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 374,164	$ 373,835
Percent of Total	100.00%	100.00%
Commercial | Total commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 133,638	$ 131,881
Percent of Total	35.70%	35.30%
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 129,434	$ 127,676
Percent of Total	34.60%	34.20%
Commercial | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 4,204	$ 4,205
Percent of Total	1.10%	1.10%
Commercial | Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 50,619	$ 53,455
Percent of Total	13.50%	14.30%
Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 39,602	$ 41,934
Percent of Total	10.60%	11.20%
Commercial | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 11,017	$ 11,521
Percent of Total	2.90%	3.10%
Consumer | Total residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 118,034	$ 115,530
Percent of Total	31.50%	30.90%
Consumer | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 111,790	$ 108,605
Percent of Total	29.90%	29.00%
Consumer | Home equity loans, first liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 6,244	$ 6,925
Percent of Total	1.60%	1.90%
Consumer | Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 29,037	$ 28,560
Percent of Total	7.80%	7.60%
Consumer | Total other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 42,836	$ 44,409
Percent of Total	11.50%	11.90%
Consumer | Retail leasing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 4,038	$ 4,135
Percent of Total	1.10%	1.10%
Consumer | Home equity and second mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 13,364	$ 13,056
Percent of Total	3.60%	3.50%
Consumer | Revolving credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 3,644	$ 3,668
Percent of Total	1.00%	1.00%
Consumer | Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 14,482	$ 13,889
Percent of Total	3.90%	3.70%
Consumer | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 7,308	$ 9,661
Percent of Total	1.90%	2.60%