GUARANTEES, LEASES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Guarantor Obligations
Credit commitments	$ 1,051,027	$ 1,030,242
Unsettled reverse repurchase and securities borrowing agreements	52,500	36,100
Unsettled repurchase and securities lending agreements	61,100	30,700
Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	5,413	5,461
One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	4,150	2,671
Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	11,052	11,374
Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	13,559	11,293
Credit card lines
Guarantor Obligations
Credit commitments	708,484	696,007
Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	304,921	300,115
Other commitments and contingencies
Guarantor Obligations
Credit commitments	3,448	$ 3,321
U.S.
Guarantor Obligations
Credit commitments	840,535
U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	928
U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	2,367
U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	9,769
U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	12,054
U.S. | Credit card lines
Guarantor Obligations
Credit commitments	613,905
U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	198,479
U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	3,033
Outside of U.S.
Guarantor Obligations
Credit commitments	210,492
Outside of U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	4,485
Outside of U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	1,783
Outside of U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	1,283
Outside of U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	1,505
Outside of U.S. | Credit card lines
Guarantor Obligations
Credit commitments	94,579
Outside of U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	106,442
Outside of U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	$ 415