MORTGAGE BANKING - Sensitivity Analysis (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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%	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%	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	9	9	11
Decline in fair value from 100 basis points adverse change in interest rates	15	18	18
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	2
Decline in fair value from 100 basis points adverse change	6	6	4