GUARANTEES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Guarantor Obligations
Credit commitments	$ 1,099,552	$ 1,031,362
Unsettled reverse repurchase and securities borrowing agreements	201,200	117,700
Unsettled repurchase and securities lending agreements	215,900	126,800
Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	4,299	4,031
One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	1,519	967
Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	5,068	5,271
Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	13,830	14,107
Credit card lines
Guarantor Obligations
Credit commitments	692,683	676,749
Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	377,081	325,329
Other commitments and contingencies
Guarantor Obligations
Credit commitments	5,072	4,908
U.S.
Guarantor Obligations
Credit commitments	903,734
U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	525
U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	901
U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	5,066
U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	11,531
U.S. | Credit card lines
Guarantor Obligations
Credit commitments	627,925
U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	252,871
U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	4,915
U.S. | Other commitments and contingencies | Federal Reserve Bank Stock
Guarantor Obligations
Credit commitments	4,500	$ 4,500
Outside of U.S.
Guarantor Obligations
Credit commitments	195,818
Outside of U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	3,774
Outside of U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	618
Outside of U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	2
Outside of U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	2,299
Outside of U.S. | Credit card lines
Guarantor Obligations
Credit commitments	64,758
Outside of U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	124,210
Outside of U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	$ 157