LOAN SALES AND SECURITIZATIONS - Residential Mortgage Portfolio, MSRs Fair Value Method Assumptions (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Residential Mortgage \| Sensitivity Analysis Fair Value Carrying Method
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]
Spread over forward interest rate swap rates	0.00%	5.00%

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746

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