Investment in 111 West 57th Partners LLC (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Jul. 02, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2013 USD ($) ft²
Investment in 111 West 57th Partners LLC [Abstract]
Company's aggregate initial investment								$ 57,250,000
Company's aggregate initial membership interest % (in hundredths)								60.30%
Other members and Sponsor initial investment								$ 37,750,000
Financing obtained by 111 W 57th Partners							$ 725,000,000
Annaly CRE LLC initial mortgage and acquisition loan repaid							$ 230,000,000
Proceeds Company recd through Investment LLC						$ 11,699,000
Amount of Capital Contr. & Proceeds returned to Capital LLC						9,868,000
Amount of proceeds retained by the Company						$ 1,831,000
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%
Percentage of outstanding shares to be owned by CEO, minimum (in hundredths)	20.00%
Noncontrolling Interest [Line Items]
Equity Method Investment, Additional Capital Contributions			$ 6,911,000
Sponsor calculation of Investment LLC aggregate investment % after dilution (in hundredths)			48.00%
Approximate gross square feet of project | ft²								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	415,929,000		415,929,000		$ 326,387,000
Escrow deposits	9,407,000		9,407,000		26,011,000
Other assets	28,790,000		28,790,000		16,370,000
Total assets	454,126,000		454,126,000		368,768,000
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Mortgage payable	312,539,000		312,539,000		230,000,000
Other liabilities	19,178,000		19,178,000		8,319,000
Total liabilities	331,717,000		331,717,000		238,319,000
Equity:
Total equity	122,409,000		122,409,000		130,449,000
Total liabilities and equity	454,126,000		454,126,000		$ 368,768,000
Income (Loss) [Abstract]
Rental income	0	$ 54,000	0	$ 337,000
Expenses	1,316,000	1,061,000	2,206,000	3,621,000
Net income (loss)	$ (1,316,000)	$ (1,007,000)	$ (2,206,000)	$ (3,284,000)
Investment LLC [Member] | Capital LLC [Member]
Noncontrolling Interest [Line Items]
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.