Commitments (Other Commitments) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Other Commitments [Line Items]
Commitments	$ 205,526	$ 199,618
Liability Related To Investments In Low Income Housing Tax Credits	500	600
Commitments to extend credit [Member]
Other Commitments [Line Items]
Commitments	193,712	185,589
Commitments to extend credit [Member] | Total commercial
Other Commitments [Line Items]
Commitments	137,164	131,762
Commitments to extend credit [Member] | Home Equity Line of Credit [Member]
Other Commitments [Line Items]
Commitments	17,089	16,803
Commitments to extend credit [Member] | Credit Card [Member]
Other Commitments [Line Items]
Commitments	32,253	30,862
Commitments to extend credit [Member] | Other [Member]
Other Commitments [Line Items]
Commitments	7,206	6,162
Standby letters of credit [Member]
Other Commitments [Line Items]
Commitments	9,149	9,843
Standby letters of credit [Member] | Remarketing Programs [Member]
Other Commitments [Line Items]
Commitments	3,900	4,100
Reinsurance Agreements [Member]
Other Commitments [Line Items]
Commitments	92	1,393
Reinsurance Agreements [Member] | Accidental Death and Dismemberment [Member]
Other Commitments [Line Items]
Maximum Exposure		1,300
Reinsurance Agreements [Member] | Credit Life Accident and Health [Member]
Other Commitments [Line Items]
Maximum Exposure	100	100
Standby bond purchase agreements [Member]
Other Commitments [Line Items]
Commitments	1,450	1,295
Other commitments [Member]
Other Commitments [Line Items]
Commitments	$ 1,123	$ 1,498