Preferred Equity and Mezzanine Loan Investments - (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan
Variable Interest Entity [Line Items]
Total	$ 138,920	$ 100,150
Texas
Variable Interest Entity [Line Items]
Concentration risk, percentage	24.30%	43.30%
New York
Variable Interest Entity [Line Items]
Concentration risk, percentage	24.10%	0.00%
Virginia
Variable Interest Entity [Line Items]
Concentration risk, percentage	10.80%	14.90%
Alabama
Variable Interest Entity [Line Items]
Concentration risk, percentage	7.10%	0.00%
South Carolina
Variable Interest Entity [Line Items]
Concentration risk, percentage	7.00%	9.40%
Kentucky
Variable Interest Entity [Line Items]
Concentration risk, percentage	5.20%	7.20%
Preferred equity and mezzanine loan investments
Variable Interest Entity [Line Items]
Investment amount	$ 140,560	$ 101,154
Deferred loan fees, net	(1,640)	(1,004)
Total	$ 138,920	$ 100,150
Number of delinquent loans \| loan	0	0

The aggregate number of delinquent loans.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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+ References

No definition available.

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Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 4
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Net carrying amount of the assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), when the reporting entity is not the VIE's primary beneficiary.

+ References

No definition available.

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Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

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