Commitments (Other Commitments) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Commitments	$ 223,779	$ 220,368
Liability Related To Investments In Low Income Housing Tax Credits	1,100	1,100
Commitments to extend credit
Other Commitments [Line Items]
Commitments	210,413	207,821
Commitments to extend credit | Total commercial
Other Commitments [Line Items]
Commitments	154,482	153,089
Commitments to extend credit | Home equity lines of credit
Other Commitments [Line Items]
Commitments	16,604	16,626
Commitments to extend credit | Credit card
Other Commitments [Line Items]
Commitments	31,132	31,019
Commitments to extend credit | Other
Other Commitments [Line Items]
Commitments	8,195	7,087
Standby letters of credit
Other Commitments [Line Items]
Commitments	9,090	9,053
Standby letters of credit | Remarketing Programs
Other Commitments [Line Items]
Commitments	3,700	3,800
Standby bond purchase agreements
Other Commitments [Line Items]
Commitments	1,543	1,448
Other commitments
Other Commitments [Line Items]
Commitments	$ 2,733	$ 2,046