GUARANTEES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Guarantor Obligations
Credit commitments	$ 885,334	$ 888,661
Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	4,947	6,102
One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	3,632	3,196
Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	14,752	14,726
Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	9,066	10,522
Credit card lines
Guarantor Obligations
Credit commitments	575,421	573,057
Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	268,257	271,076
Other commitments and contingencies
Guarantor Obligations
Credit commitments	9,259	$ 9,982
U.S.
Guarantor Obligations
Credit commitments	688,936
U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	1,114
U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	1,790
U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	12,600
U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	7,813
U.S. | Credit card lines
Guarantor Obligations
Credit commitments	482,008
U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	178,710
U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	4,901
Outside U.S.
Guarantor Obligations
Credit commitments	196,398
Outside U.S. | Commercial and similar letters of credit
Guarantor Obligations
Credit commitments	3,833
Outside U.S. | One- to four-family residential mortgages
Guarantor Obligations
Credit commitments	1,842
Outside U.S. | Revolving open-end loans secured by one- to four-family residential properties
Guarantor Obligations
Credit commitments	2,152
Outside U.S. | Commercial real estate, construction and land development
Guarantor Obligations
Credit commitments	1,253
Outside U.S. | Credit card lines
Guarantor Obligations
Credit commitments	93,413
Outside U.S. | Commercial and other consumer loan commitments
Guarantor Obligations
Credit commitments	89,547
Outside U.S. | Other commitments and contingencies
Guarantor Obligations
Credit commitments	$ 4,358