SECURED FINANCING - Mortgage Loans Payable (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Variable interest rate	91.00%	88.00%
Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 485,657	$ 511,056
Mortgage Principal	491,435	516,834
Joint Ventures \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	316,535	316,275
Mortgage Principal	$ 318,625	$ 318,664
Joint Ventures \| Commercial Mortgage Loan \| Minimum
Debt Instrument [Line Items]
Interest Rate	4.03%	4.03%
Joint Ventures \| Commercial Mortgage Loan \| Maximum
Debt Instrument [Line Items]
Interest Rate	4.96%	4.96%
Joint Ventures \| Commercial Mortgage Loan \| LIBOR
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 16,003	$ 16,125
Mortgage Principal	$ 16,325	$ 16,125
Variable interest rate	2.15%	2.75%
Virginia \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 83,412	$ 95,827
Mortgage Principal	$ 85,193	$ 97,667
Virginia \| Commercial Mortgage Loan \| Minimum
Debt Instrument [Line Items]
Interest Rate	2.34%	2.75%
Virginia \| Commercial Mortgage Loan \| Maximum
Debt Instrument [Line Items]
Interest Rate	4.55%	4.96%
Texas \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 31,799	$ 32,189
Mortgage Principal	$ 33,311	$ 33,735
Interest Rate	3.28%	3.28%
Utah \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 7,104	$ 9,703
Mortgage Principal	$ 7,122	$ 9,706
Interest Rate	3.69%	3.69%
Utah \| Commercial Mortgage Loan \| LIBOR
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 9,706	$ 7,279
Mortgage Principal	$ 9,706	$ 7,201
Variable interest rate	3.50%	3.50%
Minnesota \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 13,292	$ 13,438
Mortgage Principal	$ 13,326	$ 13,473
Interest Rate	3.69%	3.69%
Tennessee \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value		$ 12,328
Mortgage Principal		$ 12,350
Interest Rate		4.01%
Wisconsin \| Commercial Mortgage Loan
Debt Instrument [Line Items]
Mortgage Carrying Value	$ 7,806	$ 7,892
Mortgage Principal	$ 7,827	$ 7,913
Interest Rate	3.69%	3.69%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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