COMMERCIAL REAL ESTATE INVESTMENTS - Mortgage Loans Payable (Details) - Commercial Mortgage Loan - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Line Items]
Mortgage Carrying Value	$ 309,878	$ 309,686
Mortgage Principal	312,500	312,500
Three Thousand One Hundred South Mall
Mortgage Loans on Real Estate [Line Items]
Mortgage Carrying Value	12,311	12,294
Mortgage Principal	$ 12,350	$ 12,350
Interest Rate	4.014%	4.014%
Twelve Thousand One Hundred Fifty-One Jefferson
Mortgage Loans on Real Estate [Line Items]
Mortgage Carrying Value	$ 11,021	$ 11,019
Mortgage Principal	$ 11,025	$ 11,025
Interest Rate	3.578%	3.578%
Joint Venture
Mortgage Loans on Real Estate [Line Items]
Mortgage Carrying Value	$ 286,546	$ 286,373
Mortgage Principal	$ 289,125	$ 289,125
Joint Venture \| Minimum
Mortgage Loans on Real Estate [Line Items]
Interest Rate	4.03%	4.03%
Joint Venture \| Maximum
Mortgage Loans on Real Estate [Line Items]
Interest Rate	4.61%	4.61%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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Contractual interest rate for funds borrowed, under the debt agreement.

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No definition available.

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