Investment in 111 West 57th Partners LLC (Details)		1 Months Ended	3 Months Ended		12 Months Ended
	Jul. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2014	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2017 USD ($)	May 31, 2016 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
Term of loan					4 years
Extension option of loan					1 year
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
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%
Percentage of distribution on company's initial investment to be received prior to CEO receiving percentage distribution				150.00%
Capital contributed by Capital LLC		$ 9,868,000			$ 0	$ 9,868,000
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%
Net proceeds distributed to partners in July 2015					$ 0	11,699,000
Capital contributions					0	6,911,000
Difference between the Company's carrying amount and the underlying equity					867,000
Impairment on the Company's equity method investments					0	0
Assets [Abstract]
Real estate held for development, net					563,133,000	440,370,000
Escrow deposits					9,000,000	9,400,000
Other assets					6,908,000	26,827,000
Total assets					579,041,000	476,597,000
Liabilities [Abstract]
Loans payable					441,749,000	340,693,000
Other liabilities					16,788,000	14,447,000
Total liabilities					458,537,000	355,140,000
Equity [Abstract]
Total members' equity					120,504,000	121,457,000
Total liabilities and members' equity					579,041,000	476,597,000
Income (Loss) [Abstract]
Rental income					0	0
Expenses					953,000	3,158,000
Net income (loss)					$ (953,000)	$ (3,158,000)
Capital LLC [Member]
Noncontrolling Interest [Line Items]
Percentage of outstanding shares to be owned by CEO					20.00%
Line of Credit [Member] | R. A. Bianco [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity								$ 1,000,000
Subsequent Event [Member] | Line of Credit [Member] | R. A. Bianco [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity							$ 10,000,000
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 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.