COMMITMENTS AND CONTINGENCIES - Narrative (Details) $ in Millions	1 Months Ended		6 Months Ended		12 Months Ended		78 Months Ended
	Jun. 30, 2015 USD ($)	Apr. 30, 2013 USD ($)	Jun. 30, 2015 USD ($) counterparty	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2003	Jun. 30, 2015 USD ($)
Risk Participation Agreements [Abstract]
Risk participation agreements	$ 22		$ 22		$ 19		$ 22
Risk participation agreements number of counterparties | counterparty			80
Risk participation agreements, Maximum term			10 years
Mortgage Repurchase Demands [Abstract]
Mortgage repurchase demands received							165
Indemnification payment requests received							99
Repurchased mortgage loans			$ 7	$ 17			95
Indemnification payment requests paid			0	7			33
Payments for Repurchase of Mortgage Loans			$ 7	$ 17
Consent Orders
Consumer Products [Abstract]
Litigation settlement amount		$ 10
Restitution amount payable		$ 8
Minimum
Risk Participation Agreements [Abstract]
Risk participation agreements, Average term			1 year
Maximum
Risk Participation Agreements [Abstract]
Risk participation agreements, Average term			5 years
Letter of Credit
Letters of Credit [Abstract]
Letters of credit outstanding	1		$ 1		3		1
Marketing rights
Marketing Rights [Abstract]
Commitment period						25 years
Payments made			2		$ 3
Remaining obligation due	49		49				49
Student
Commitments [Abstract]
Payments to Acquire Loans Held-for-investment	202
Purchase obligation, cumulative maximum amount	700		700				700
Student | Minimum
Commitments [Abstract]
Purchase commitment, due in next twelve months	100		100				100
Student | Maximum
Commitments [Abstract]
Purchase commitment, due in next twelve months	163		163				163
Automobile | Minimum
Commitments [Abstract]
Purchase commitment, due in next twelve months	250		250				250
Purchase commitment, due after next twelve months	50		50				50
Automobile | Maximum
Commitments [Abstract]
Purchase commitment, due in next twelve months	600		600				600
Purchase commitment, due after next twelve months	200		200				200
Purchase Commitment | Commercial real estate loans held for sale
Commitments [Abstract]
Unsettled commercial loan trades	$ 96		96				$ 96
Loans and Leases Receivable, Commitments to Purchase or Sell			$ 102
Financial standby letters of credit
Letters of Credit [Abstract]
Guarantor Obligations, Term			P10Y
Performance letters of credit
Letters of Credit [Abstract]
Guarantor Obligations, Term			P10Y
Commercial letters of credit
Letters of Credit [Abstract]
Guarantor Obligations, Term			P1Y