MORTGAGE BANKING - Changes Related to MSRs (Details) (Residential Mortgages, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Residential Mortgages
MSRs
Balance as of January 1	$ 208	$ 215	$ 215
Amount capitalized	17	45	67
Amortization	(41)	(52)	(67)
Carrying amount before valuation allowance	184	208	215
Valuation allowance for servicing assets
Balance as of January 1	23	70	58
Valuation (recovery) impairment	(5)	(47)	12
Balance at end of period	18	23	70
Net carrying value of MSRs	$ 166	$ 185	$ 145