MORTGAGE BANKING - Changes Related to MSRs (Details) - Residential mortgages - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
MSRs
Balance as of January 1	$ 184	$ 208
Amount capitalized	20	13
Amortization	(28)	(32)
Carrying amount before valuation allowance	176	189
Valuation allowance for servicing assets
Balance as of January 1	18	23
Valuation recovery	(6)	(8)
Balance at end of period	12	15
Net carrying value of MSRs	$ 164	$ 174