GUARANTEES AND COMMITMENTS - Credit Commitments and Lines of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Credit Commitments
Credit commitments	$ 896,183	$ 904,040
Commercial and similar letters of credit
Credit Commitments
Credit commitments	5,311	6,634
One-to four-family residential mortgages
Credit Commitments
Credit commitments	3,389	5,674
Revolving open-end loans secured by one-to four-family residential properties
Credit Commitments
Credit commitments	15,037	16,098
Commercial real estate, construction and land development
Credit Commitments
Credit commitments	10,185	9,242
Credit card lines
Credit Commitments
Credit commitments	589,364	612,049
Commercial and other consumer loan commitments
Credit Commitments
Credit commitments	262,732	243,680
Commercial and other consumer loan commitments original maturity of less than 1 year	54,000	53,000
Other commitments and contingencies
Credit Commitments
Credit commitments	10,165	$ 10,663
U.S.
Credit Commitments
Credit commitments	681,505
U.S. | Commercial and similar letters of credit
Credit Commitments
Credit commitments	1,207
U.S. | One-to four-family residential mortgages
Credit Commitments
Credit commitments	1,375
U.S. | Revolving open-end loans secured by one-to four-family residential properties
Credit Commitments
Credit commitments	12,952
U.S. | Commercial real estate, construction and land development
Credit Commitments
Credit commitments	8,456
U.S. | Credit card lines
Credit Commitments
Credit commitments	479,415
U.S. | Commercial and other consumer loan commitments
Credit Commitments
Credit commitments	173,439
U.S. | Other commitments and contingencies
Credit Commitments
Credit commitments	4,661
Outside U.S.
Credit Commitments
Credit commitments	214,678
Outside U.S. | Commercial and similar letters of credit
Credit Commitments
Credit commitments	4,104
Outside U.S. | One-to four-family residential mortgages
Credit Commitments
Credit commitments	2,014
Outside U.S. | Revolving open-end loans secured by one-to four-family residential properties
Credit Commitments
Credit commitments	2,085
Outside U.S. | Commercial real estate, construction and land development
Credit Commitments
Credit commitments	1,729
Outside U.S. | Credit card lines
Credit Commitments
Credit commitments	109,949
Outside U.S. | Commercial and other consumer loan commitments
Credit Commitments
Credit commitments	89,293
Outside U.S. | Other commitments and contingencies
Credit Commitments
Credit commitments	$ 5,504