SECURITIES - Schedule of Balance Sheet Effect of Repurchase Agreement Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Securities purchased under agreements to resell, gross	$ 1,300	$ 0
Securities purchased under agreements to resell, offset	(1,300)	0
Securities purchased under agreements to resell, net	0	0
Securities sold under agreements to repurchase, gross	(1,800)	(2,600)
Securities sold under agreements to repurchase, offset	1,300	0
Securities sold under agreements to repurchase, net	$ (500)	$ (2,600)