GUARANTEES, LEASES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Guarantor Obligations
Credit commitments	$ 1,055,582	$ 1,066,364
Unsettled reverse repurchase and securities borrowing agreements	63,000	34,000
Unsettled repurchase and securities lending agreements	72,500	38,700
Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	4,003	4,533
One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	5,270	3,721
Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	10,409	10,799
Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	12,392	12,981
Credit card lines
Guarantor Obligations
Credit commitments	714,451	708,023
Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	306,380	324,359
Other commitments and contingencies
Guarantor Obligations
Credit commitments	2,677	$ 1,948
U.S.
Guarantor Obligations
Credit commitments	840,097
U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	582
U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	2,948
U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	9,129
U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	10,617
U.S. | Credit card lines
Guarantor Obligations
Credit commitments	616,582
U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	198,358
U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	1,881
Outside of  U.S.
Guarantor Obligations
Credit commitments	215,485
Outside of  U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	3,421
Outside of  U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	2,322
Outside of  U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	1,280
Outside of  U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	1,775
Outside of  U.S. | Credit card lines
Guarantor Obligations
Credit commitments	97,869
Outside of  U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	108,022
Outside of  U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	$ 796