SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Carrying Amounts and Classifications of Consolidated Assets (Details) $ in Millions	Sep. 30, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Variable Interest Entity
Cash	$ 21,726	$ 32,108	$ 35,976	$ 29,885
Trading account assets	266,946	296,786
Investments	342,439	333,443
Total loans, net	608,818	628,641
Other assets	132,832	122,122
Total assets	1,808,356	1,842,181
Consolidated VIEs
Variable Interest Entity
Cash	200	300
Trading account assets	600	700
Investments	5,600	8,000
Total loans, net	80,700	93,200
Other assets	8,700	600
Total assets	95,800	102,800
Short-term borrowings	13,800	22,700
Long-term debt	32,400	40,100
Other liabilities	6,500	900
Total Liabilities	52,700	63,700
Non-recourse liabilities	$ 50,500	61,200
With recourse liabilities, number of items | item	2
Consolidated VIEs | Letter of credit
Variable Interest Entity
Total Liabilities	$ 2,200	2,200
Consolidated VIEs | Credit guarantee
Variable Interest Entity
With recourse liabilities	83	198
Significant unconsolidated VIE assets
Variable Interest Entity
Cash	100	0
Trading account assets	5,900	7,600
Investments	2,800	2,600
Total loans, net	26,400	25,000
Other assets	1,800	2,000
Total assets	$ 37,000	$ 37,200