Commitments (Other Commitments) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Commitments	$ 255,054	$ 220,368
Liability Related To Investments In Low Income Housing Tax Credits	1,700	1,100
Commitments to extend credit
Other Commitments [Line Items]
Commitments	241,514	207,821
Commitments to extend credit | Total commercial
Other Commitments [Line Items]
Commitments	177,033	153,089
Commitments to extend credit | Home equity lines of credit
Other Commitments [Line Items]
Commitments	19,300	16,626
Commitments to extend credit | Credit card
Other Commitments [Line Items]
Commitments	34,488	31,019
Commitments to extend credit | Other
Other Commitments [Line Items]
Commitments	10,693	7,087
Standby letters of credit
Other Commitments [Line Items]
Commitments	9,495	9,053
Standby letters of credit | Remarketing Programs
Other Commitments [Line Items]
Commitments	3,400	3,800
Standby bond purchase agreements
Other Commitments [Line Items]
Commitments	1,300	1,448
Other commitments
Other Commitments [Line Items]
Commitments	$ 2,745	$ 2,046