Investment in 111 West 57th Partners LLC (Details)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jul. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Jun. 28, 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 percentage									60.30%
Other members and Sponsor initial investment									$ 37,750,000
Approximate gross square feet of project | ft²									346,000
Financing obtained by 111 W 57th Partners		$ 725,000,000
Annaly CRE LLC initial mortgage and acquisition loan repaid		$ 230,000,000
Distribution attributable to Company's investment	$ 11,699,000
Distribution retained by the Company, net of amounts repaid to Capital LLC	$ 1,831,000
Capital contributed by Capital LLC			$ 9,868,000			$ 0	$ 9,868,000
Term of loan						4 years
Extension option of loan						1 year
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) 50% to the Sponsor.
Subordinated participation interest to CEO				10.00%		10.00%
Percentage of distribution on company's initial investment to be received prior to CEO receiving percentage distribution						150.00%
Noncontrolling Interest [Line Items]
Capital contributions						$ 0
Valuation of shortfall capital contribution as multiple of amount actually contributed						1.5
Sponsor calculation of investment LLC aggregate investment percentage after dilution						48.00%
Difference between the Company's carrying amount and the underlying equity				$ 867,000		$ 867,000
Impairment on the Company's equity method investments						0		$ 0
Assets [Abstract]
Real estate held for development, net				535,734,000		535,734,000		440,370,000
Escrow deposits				9,400,000		9,400,000		9,400,000
Other assets				16,665,000		16,665,000		26,827,000
Total assets				561,799,000		561,799,000		476,597,000
Liabilities [Abstract]
Loans payable				422,584,000		422,584,000		340,693,000
Other liabilities				18,668,000		18,668,000		14,447,000
Total liabilities				441,252,000		441,252,000		355,140,000
Equity [Abstract]
Total members' equity				120,547,000		120,547,000		121,457,000
Total liabilities and members' equity				561,799,000		561,799,000		$ 476,597,000
Income (Loss) [Abstract]
Rental income				0	$ 0	0	0
Expenses				81,000	1,316,000	910,000	2,206,000
Net income (loss)				$ (81,000)	$ (1,316,000)	$ (910,000)	$ (2,206,000)
Minimum [Member]
Noncontrolling Interest [Line Items]
Percentage of outstanding shares to be owned by CEO						20.00%
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 as noted above), 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 above 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.