INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Mortgage Loans on Real Estate [Line Items]
Threshold period past due (in days)	60 days
Government Guaranteed Mortgage Loans upon Foreclosure Receivable
Mortgage Loans on Real Estate [Line Items]
Claims receivable	$ 41.4
Residential Mortgage Loans
Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 429.7

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant