Investment in 111 West 57th Partners LLC (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) ft²	Jun. 30, 2015 USD ($)
Investment in 111 West 57th Partners LLC [Abstract]
Percentage ownership (in hundredths)			60.30%
Additional contributions made by other partners in the agreement			$ 37,750,000
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 (in hundredths)	10.00%
Percentage of distribution on company's initial investment expected to be received (in hundredths)	150.00%
Initial aggregate investment in Investment LLC			$ 57,250,000
Noncontrolling Interest [Line Items]
Additional capital contributions		$ 6,911,000
Sponsor calculation of Investment LLC aggregate investment % after dilution (in hundredths)		48.00%
Area of Real Estate Property | 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
Net proceeds distributed to partners in July 2015		$ 11,699,000	$ 0
Amount of proceeds retained by the Company		1,831,000
Amount of Capital Contr. & Proceeds returned to Capital LLC		9,868,000
Payments to Acquire Equity Method Investments		6,911,000	17,010,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		867,000
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Real estate held for development, net		440,370,000	326,387,000
Escrow deposits		9,400,000	26,011,000
Other assets		26,827,000	16,370,000
Total assets		476,597,000	368,768,000
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Mortgage payable		340,693,000	230,000,000
Other liabilities		14,447,000	8,319,000
Total liabilities		355,140,000	238,319,000
Equity:
Total equity		121,457,000	130,449,000
Total liabilities and equity		476,597,000	368,768,000
Income (Loss) [Abstract]
Rental income		0	1,039,000
Expenses		3,158,000	4,526,000
Net income (loss)		$ (3,158,000)	$ (3,487,000)
Investment LLC [Member] | Capital LLC [Member]
Noncontrolling Interest [Line Items]
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 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.