SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Carrying Amounts and Classifications of Consolidated Assets (Details) $ in Millions	Mar. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Variable Interest Entity
Cash and due from banks	$ 22,240	$ 20,900	$ 21,880	$ 32,108
Trading account assets	273,747	249,956
Investments	353,252	342,955
Total loans, net of allowance	606,112	604,991
Other	121,621	125,002
Total assets	1,800,967	1,731,210
Consolidated VIEs
Variable Interest Entity
Cash and due from banks	200	200
Trading account assets	600	600
Investments	5,200	5,300
Total loans, net of allowance	74,900	78,600
Other	100	100
Total assets	81,000	84,800
Short-term borrowings	13,600	14,000
Long-term debt	29,100	31,300
Other liabilities	2,000	2,100
Total Liabilities	44,700	47,400
Non-recourse liabilities	$ 42,700	45,300
With recourse liabilities, number of items | item	2
Consolidated VIEs | Letter of credit
Variable Interest Entity
Total Liabilities	$ 1,900	1,900
Consolidated VIEs | Credit guarantee
Variable Interest Entity
With recourse liabilities	82	82
Significant unconsolidated VIE assets
Variable Interest Entity
Cash and due from banks	100	100
Trading account assets	7,700	6,200
Investments	3,500	3,000
Total loans, net of allowance	21,700	23,600
Other	1,400	1,700
Total assets	$ 34,400	$ 34,600