MORTGAGE BANKING - Sensitivity Analysis (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Adverse change in basis points	0.50%	0.50%
Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Adverse change in basis points	1.00%	1.00%
Prepayment rate
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Decline in fair value from 50 basis points adverse change in interest rates	6	9
Decline in fair value from 100 basis points adverse change in interest rates	12	15
Weighted average discount rate
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Decline in fair value from 50 basis points adverse change	3	3
Decline in fair value from 100 basis points adverse change	6	6