Investment in 111 West 57th Partners LLC (Details)	1 Months Ended		3 Months Ended			6 Months Ended	12 Months Ended
	Apr. 30, 2015 USD ($)	Feb. 28, 2015 USD ($)	Jun. 30, 2015 USD ($) ft²	Jun. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)
Investment in 111 West 57th Partners LLC [Abstract]
Amount of the investment			$ 56,000,000			$ 56,000,000
Percentage ownership (in hundredths)			59.00%			59.00%
Additional indirect contribution			$ 1,250,000			$ 1,250,000
Additional ownership acquired through indirect contribution (in hundredths)			1.30%			1.30%
Additional contributions made by other partners in the agreement			$ 37,750,000			$ 37,750,000
Financing obtained for 111 W 57th			725,000,000			725,000,000
Amount of Annaly acquisition loan repaid			230,000,000			230,000,000
Net proceeds distributed to partners in July 2015			24,682,000			24,682,000
Proceeds Company recd through Investment LLC			11,895,000			11,895,000
Amount of Proceeds returned to Capital LLC			9,895,000			9,895,000
Amount of proceeds retained by the Company			$ 2,000,000			$ 2,000,000
Description of partnership agreement distribution						The JV Agreement and related operating agreements generally provide that all distributable cash shall be distributed as follows: (i) first, 100% to the members in proportion to their percentage interests until Investment LLC has received distributions yielding a 20% internal rate of return as calculated; (ii) second, 100% to the Sponsor as a return of (but not a return on) any additional capital contributions made by the Sponsor on account of manager overruns; and (iii) thereafter, (a) 50% to the members in proportion to their respective percentage interests at the time of such distribution, and (b) fifty percent 50% to the Sponsor.
Subordinated participation interest to CEO (in hundredths)			10.00%			10.00%
Percentage of distribution on company's initial investment to be received prior to CEO receiving percentage distribution (in hundredths)			150.00%
Initial aggregate investment in Investment LLC			$ 57,250,000			$ 57,250,000
Percentage of outstanding shares to be owned by CEO, minimum (in hundredths)			20.00%
Noncontrolling Interest [Line Items]
Percentage of outstanding shares to be owned by CEO, minimum (in hundredths)			20.00%
Equity Method Investment, Additional Capital Contributions						$ 6,911,000
Amount Company was to contribute to Joint Venture pursuant to capital call	$ 6,200,000	$ 7,500,000					$ 10,300,000
Amount of contribution to Joint Venture pursuant to capital call	400,000	$ 700,000					$ 1,500,000
Sponsor calculation of Investment LLC aggregate investment % after dilution (in hundredths)							48.00%
Area of Real Estate Property | ft²			346,000			346,000
Subsequent Event [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity			$ 867,000			$ 867,000
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Real estate held for development, net			378,935,000			378,935,000	$ 326,387,000
Escrow deposits			9,407,000			9,407,000	26,011,000
Other assets			49,383,000			49,383,000	16,370,000
Total assets			437,725,000			437,725,000	368,768,000
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Mortgage payable			278,226,000			278,226,000	230,000,000
Other liabilities			12,072,000			12,072,000	8,319,000
Total liabilities			290,298,000			290,298,000	238,319,000
Equity:
Total equity			147,427,000			147,427,000	130,449,000
Total liabilities and equity			437,725,000			437,725,000	$ 368,768,000
Income (Loss) [Abstract]
Rental income			0	$ 10,000	$ 283,000	0
Expenses			473,000	1,290,000	2,560,000	890,000
Net income (loss)			$ (473,000)	$ (1,280,000)	$ (2,277,000)	$ (890,000)
Investment LLC [Member] | Capital LLC [Member]
Investment in 111 West 57th Partners LLC [Abstract]
Percentage of outstanding shares to be owned by CEO, minimum (in hundredths)							20.00%
Noncontrolling Interest [Line Items]
Contribution to Investment LLC by non-controlling interest							$ 4,100,000
Percentage of outstanding shares to be owned by CEO, minimum (in hundredths)							20.00%
Terms of distributions to Capital LLC							available cash of Investment LLC will be distributed first to Capital LLC until it has received a 20% internal rate of return (calculated as provided for in the JV Agreement), second to the Company until it has received 150% of its capital, and; thereafter, available cash is split 10/90 with 10% going to Mr. R.A. Bianco as the subordinated participation interest noted and 90% going to Capital LLC and the Company pari-passu, with Capital LLC receiving one-half of its pro-rata share based on capital contributed and the Company receiving the balance.
Investment LLC [Member] | Capital LLC [Member] | Subsequent Event [Member]
Noncontrolling Interest [Line Items]
Contribution to Investment LLC by non-controlling interest	$ 5.8