SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Municipal Securities Tender Option Bond Trusts (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) trust Class	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Variable Interest Entity
Number of classes of certificates | Class	2
Number of TOB trusts | trust	2
Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Floater inventory held by entity	$ 119		$ 2
Municipal bonds owned by trusts, that have credit guarantee provided by the Company	82		82
Liquidity agreements, customer TOB trust	3,000		3,100
Notional amount of offsetting reimbursement agreements	2,200		2,200
Liquidity agreements, other trusts	$ 7,600		$ 8,100
Maximum | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
The threshold ownership percentage on Residual value of customers TOBs for which the reimbursement agreement applied	25.00%
Client intermediation
Variable Interest Entity
Proceeds from new securitizations	$ 600	$ 200