Loans and Investments, Risk Ratings and LTV Ratios (Details)	12 Months Ended
Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) item
Loans and Investments
Unpaid Principal Balance	$ 1,545,126,045	$ 1,587,429,498
Percentage of Portfolio	100.00%	100.00%
First Dollar LTV Ratio (as percent)	7.00%	13.00%
Last Dollar LTV Ratio (as percent)	76.00%	76.00%
Loans and investments portfolio \| New York
Loans and Investments
Concentration risk, percentage	34.00%	28.00%
Loans and investments portfolio \| Florida
Loans and Investments
Concentration risk, percentage	14.00%	10.00%
Loans and investments portfolio \| California
Loans and Investments
Concentration risk, percentage	14.00%
Loans and investments portfolio \| Texas
Loans and Investments
Concentration risk, percentage	12.00%	14.00%
Credit risk concentration
Loans and Investments
Unpaid Principal Balance	$ 1,545,126,045	$ 1,587,429,498
Percentage of Portfolio	100.00%	100.00%
First Dollar LTV Ratio (as percent)	7.00%	13.00%
Last Dollar LTV Ratio (as percent)	76.00%	76.00%
Credit risk concentration \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.1	3.1
Credit risk concentration \| Multifamily
Loans and Investments
Unpaid Principal Balance	$ 1,083,822,788	$ 1,157,462,400
Percentage of Portfolio	70.10%	72.90%
First Dollar LTV Ratio (as percent)	2.00%	10.00%
Last Dollar LTV Ratio (as percent)	75.00%	73.00%
Credit risk concentration \| Multifamily \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.0	2.9
Credit risk concentration \| Office
Loans and Investments
Unpaid Principal Balance	$ 198,829,086	$ 230,491,164
Percentage of Portfolio	12.90%	14.50%
First Dollar LTV Ratio (as percent)	27.00%	29.00%
Last Dollar LTV Ratio (as percent)	75.00%	79.00%
Credit risk concentration \| Office \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.0	3.3
Credit risk concentration \| Land
Loans and Investments
Unpaid Principal Balance	$ 164,410,838	$ 128,367,601
Percentage of Portfolio	10.60%	8.10%
First Dollar LTV Ratio (as percent)	5.00%	6.00%
Last Dollar LTV Ratio (as percent)	90.00%	88.00%
Credit risk concentration \| Land \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.8	3.9
Credit risk concentration \| Hotel
Loans and Investments
Unpaid Principal Balance	$ 66,250,000	$ 66,250,000
Percentage of Portfolio	4.30%	4.20%
First Dollar LTV Ratio (as percent)	32.00%	32.00%
Last Dollar LTV Ratio (as percent)	80.00%	83.00%
Credit risk concentration \| Hotel \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.5	3.5
Credit risk concentration \| Other
Loans and Investments
Unpaid Principal Balance	$ 31,813,333	$ 4,858,333
Percentage of Portfolio	2.10%	0.30%
First Dollar LTV Ratio (as percent)	13.00%	69.00%
Last Dollar LTV Ratio (as percent)	67.00%	75.00%
Credit risk concentration \| Other \| Weighted average
Loans and Investments
Wtd. Avg. Internal Risk Rating \| item	3.1	2.9

Represents the individual ratings assigned to credit risk during the loan valuation and risk assessment process.

No definition available.

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- Definition

Represents the First Dollar LTV Ratio that is calculated by comparing the total of the company's senior most dollar and all senior lien positions within the capital stack to the fair value of the underlying collateral to determine the point at which the company will absorb a total loss of its position.

+ References

No definition available.

+ Details

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- Definition

Represents the weighted average loan to value ratio that is calculated by comparing the total of the carrying value of the company's loan and all senior lien positions within the capital stack to the fair value of the underlying collateral to determine the point at which the company will initially absorb a loss.

+ References

No definition available.

+ Details

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- Definition

Represents a category of loans on real estate expressed as a percentage of total loans on real estate.

+ References

No definition available.

+ Details

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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=51801978&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13537-108611

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- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

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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.

+ Details

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- Details

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