MORTGAGE BANKING - Changes Related to MSRs (Details) - Residential mortgages - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
MSRs
Balance as of January 1	$ 184	$ 208
Amount capitalized	13	8
Amortization	(20)	(21)
Carrying amount before valuation allowance	177	195
Valuation allowance for servicing assets
Balance as of January 1	18	23
Valuation recovery	(7)	(3)
Balance at end of period	11	20
Net carrying value of MSRs	$ 166	$ 175