GUARANTEES, LEASES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Guarantor Obligations
Credit commitments	$ 1,062,461	$ 1,066,364
Unsettled reverse repurchase and securities borrowing agreements	68,800	34,000
Unsettled repurchase and securities lending agreements	62,000	38,700
Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	4,576	4,533
One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	5,404	3,721
Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	9,908	10,799
Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	13,790	12,981
Credit card lines
Guarantor Obligations
Credit commitments	711,862	708,023
Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	314,049	324,359
Other commitments and contingencies
Guarantor Obligations
Credit commitments	2,872	$ 1,948
U.S.
Guarantor Obligations
Credit commitments	840,772
U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	643
U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	3,298
U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	8,622
U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	12,126
U.S. | Credit card lines
Guarantor Obligations
Credit commitments	612,777
U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	201,036
U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	2,270
Outside of  U.S.
Guarantor Obligations
Credit commitments	221,689
Outside of  U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	3,933
Outside of  U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	2,106
Outside of  U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	1,286
Outside of  U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	1,664
Outside of  U.S. | Credit card lines
Guarantor Obligations
Credit commitments	99,085
Outside of  U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	113,013
Outside of  U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	$ 602