FAIR VALUE MEASUREMENTS - Schedule of Fair Value Measurements on a Nonrecurring Basis (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill	$ 6,876	$ 6,876		$ 11,311
Goodwill impairment	0	4,435		0
Residential Mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net carrying value of MSRs	166	185		145
Servicing Asset at Amortized Cost	184	208		215	215
Valuation (recovery) impairment	5	47		(12)
Cumulative valuation allowance on mortgage servicing rights	18	23		70	58
Nonrecurring measurement basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired collateral-dependent loans	102	74
Mortgage Servicing Rights	166	185
Foreclosed assets	40	49
Goodwill		6,876	[1]
Level 1 | Nonrecurring measurement basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired collateral-dependent loans	0	0
Mortgage Servicing Rights	0	0
Foreclosed assets	0	0
Goodwill		0	[1]
Level 2 | Nonrecurring measurement basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired collateral-dependent loans	102	74
Mortgage Servicing Rights	0	0
Foreclosed assets	40	49
Goodwill		0	[1]
Level 3 | Nonrecurring measurement basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired collateral-dependent loans	0	0
Mortgage Servicing Rights	166	185
Foreclosed assets	0	0
Goodwill		$ 6,876	[1]

[1] In the year ended December 31, 2013, Goodwill totaling $11.3 billion was written down to its implied fair value of $6.9 billion, resulting in an impairment charge of $4.4 billion.