Acquisitions, Disposition, Leasing and Financing Activities - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended				12 Months Ended	1 Months Ended		12 Months Ended			0 Months Ended		11 Months Ended	1 Months Ended	0 Months Ended				3 Months Ended				0 Months Ended					3 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	2 Months Ended	0 Months Ended	2 Months Ended	12 Months Ended	0 Months Ended				0 Months Ended			1 Months Ended		12 Months Ended	0 Months Ended	12 Months Ended					0 Months Ended	12 Months Ended				1 Months Ended					12 Months Ended				0 Months Ended	1 Months Ended	12 Months Ended		0 Months Ended		3 Months Ended	9 Months Ended
	Jun. 02, 2012	Aug. 31, 2013	Dec. 31, 2013 Parcels	Dec. 31, 2012	Dec. 31, 2011	Oct. 07, 2013	Dec. 31, 2013 Churchill [Member]	Mar. 31, 2013 Playa Vista Mezzanine Loan [Member]	Jan. 31, 2013 Playa Vista Mezzanine Loan [Member] sqft	Dec. 31, 2013 Playa Vista Mezzanine Loan [Member]	Feb. 28, 2013 Playa Vista Mezzanine Loan [Member]	Jan. 24, 2013 Playa Vista Mezzanine Loan [Member]	Jan. 31, 2013 Nonperforming Loans Receivable [Member]	Dec. 12, 2012 Nonperforming Loans Receivable [Member] Building sqft	Dec. 31, 2013 Nonperforming Loans Receivable [Member]	Jun. 11, 2013 Deer Valley [Member]	Jul. 02, 2013 Denton Property Sale [Member]	Aug. 02, 2013 Seabrook Property Sale [Member]	Nov. 06, 2013 New Valley LLC [Member]	Jun. 14, 2013 Fenway Shea Loan Asset [Member]	Jun. 30, 2013 Westheimer [Member]	Dec. 31, 2012 Westheimer [Member]	Dec. 31, 2013 Westheimer [Member]	Jun. 28, 2013 First Mortgage [Member] Churchill [Member]	Mar. 02, 2013 127 West 25th Street [Member]	Mar. 28, 2013 180 N. Michigan [Member]	Oct. 31, 2013 Renaissance Walk [Member]	Mar. 28, 2013 Andover, Massachusetts Property Sale [Member]	Dec. 17, 2013 Lisle Illinois Property Sale [Member]	Mar. 31, 2013 Houston, Texas Operating Property [Member]	Dec. 31, 2013 Houston, Texas Operating Property [Member] Westheimer [Member]	Jul. 29, 2013 Amherst Property Acquisition [Member] sqft	Dec. 31, 2013 Amherst Property Acquisition [Member] Extension	Oct. 18, 2013 Wrt Elad Equity Mortgage Loan Refinancing [Member]	Dec. 31, 2013 Wrt Elad Equity Mortgage Loan Refinancing [Member]	Oct. 15, 2013 WRT-Fenway Wateridge - Mortgage Loan [Member]	Dec. 31, 2013 WRT-Fenway Wateridge - Mortgage Loan [Member]	Oct. 25, 2013 Summit Pointe Apartments [Member] Apartment	Dec. 31, 2013 Summit Pointe Apartments [Member]	Oct. 31, 2013 Luxury Residential [Member] Apartment sqft	Dec. 31, 2013 Luxury Residential [Member]	Dec. 31, 2013 Luxury Residential [Member] Apartment	Oct. 31, 2013 Interest Rate Caps [Member] Luxury Residential [Member]	Oct. 31, 2013 Interest Rate Cap One [Member] Luxury Residential [Member]	Oct. 31, 2013 Interest Rate Cap Two [Member] Luxury Residential [Member]	Oct. 25, 2013 Minimum [Member] Summit Pointe Apartments [Member]	Jul. 29, 2013 Rent Under Lease Period October Two Thousand Eighteen [Member] Amherst Property Acquisition [Member]	Jul. 29, 2013 Rent Under Lease Period October Two Thousand Twenty Three [Member] Amherst Property Acquisition [Member]	Aug. 21, 2013 WRT-Elad One South State Lender LP [Member]	Nov. 30, 2013 WRT-Elad One South State Lender LP [Member]	Feb. 28, 2013 WRT-Elad One South State Lender LP [Member]	Dec. 31, 2013 WRT-Elad One South State Lender LP [Member]	Feb. 20, 2013 RE CDO Management LLC [Member]	Dec. 31, 2013 RE CDO Management LLC [Member]	Mar. 08, 2013 RE CDO Management LLC [Member]	Dec. 31, 2012 RE CDO Management LLC [Member]	Dec. 31, 2011 RE CDO Management LLC [Member]	Dec. 31, 2013 RE CDO Management LLC [Member] First Mortgage [Member]	Feb. 25, 2013 CDH CDO LLC [Member]	Dec. 31, 2013 CDH CDO LLC [Member]	Dec. 31, 2012 CDH CDO LLC [Member]	Dec. 31, 2011 CDH CDO LLC [Member]	Dec. 31, 2013 WRT Elad Management LLC [Member]	Aug. 31, 2012 10 Metrotech Loan LLC [Member]	Dec. 31, 2013 10 Metrotech Loan LLC [Member]	Jul. 30, 2013 10 Metrotech Loan LLC [Member]	Dec. 31, 2012 10 Metrotech Loan LLC [Member]	Dec. 31, 2011 10 Metrotech Loan LLC [Member]	Dec. 31, 2013 701 Seventh Avenue [Member]	Dec. 31, 2013 MPG Office Trust Inc [Member]	Dec. 31, 2013 Cedar Realty Trust Inc [Member]	Dec. 31, 2013 Recourse Secured Financings [Member] Queensridge Towers [Member]	Jan. 26, 2013 Burbank Centre [Member]	Jan. 31, 2014 Subsequent Event [Member] 701 Seventh Avenue [Member]	Dec. 31, 2013 1515 Market Street Loan Modification [Member] Original Mortgage [Member]	Apr. 25, 2013 1515 Market Street Loan Modification [Member] Original Mortgage [Member]	Apr. 25, 2013 1515 Market Street Loan Modification [Member] First Mortgage [Member]	Dec. 31, 2013 1515 Market Street Loan Modification [Member] First Mortgage [Member]	Jun. 30, 2013 Atrium Property [Member]	Sep. 30, 2013 Atrium Property [Member] Times sqft	Dec. 02, 2013 Sealy Newmarket [Member]
Business Acquisition [Line Items]
Amount acquired through loan on mortgage			$ 101,100,000											$ 58,650,000																																												$ 21,227,000																	$ 36,171,000	$ 33,157,000				$ 10,650,000
Face Value			142,631,000							80,300,000				70,000,000										5,100,000										113,500,000		7,000,000																																									43,000,000
Number of stories														20
Loan collateralized														514,000
Increase outstanding principal amount													71,629,000
Unpaid interest and expenses and advances													70,000,000
Mortgage loans on real estate adjusted interest rate minimum													7.50%
LIBOR plus													6.50%
Maturity date of loan															Feb. 01, 2016
Payment to acquire indirect interest													10,000
Acquired interest rate through indirect													49.00%
Loan bears interest, description of variable rate basis																																																																													LIBOR plus 2.0%
Maturity date of loan							Aug. 01, 2024		Jan. 23, 2015																										Nov. 06, 2018		Nov. 01, 2016					Oct. 31, 2016																																			May 01, 2016
Mortgage loan, LIBOR rate																																								0.69%																																					0.50%
Loan proceeds received																																																																													38,472,000
Percentage for participation																																																																												40.00%
Increased loan balance through future funding advances																																																																													6,000,000
Future advances																																																																													500,000	1,500,000
Interest rate increase for each future advances																																																																													0.10%	0.30%
Interest rate , loan bears							3.50%																											3.95%				5.70%																																					14.30%
Mortgage loans on real estate reduced investment amount																																																																											21,098,000
Mortgage loans on real estate effective interest rate on investment																																																																											19.60%
Additional contribution	5,850,000		30,341,000	78,679,000	151,219,000																75,000	1,650,000								75,000								4,962,000																															24,465,000					33,419,000
Additional interest in joint venture acquired																																				50.00%		80.00%											50.00%			50.00%	50.00%										100.00%	33.33%
Apartment units acquired																																						184		4		761
Aggregate purchase price			896,000																																			14,500,000		246,000,000
Existing Mortgage Loan Carrying Amount			559,115,000																															110,550,000				9,248,000
Preferred return from cash flow																																						8.00%
Minimum IRR																																														12.00%
Mortgage loan, maturity date																																						2021-02
Retail space																																								25,000
First mortgage loan																																								150,000,000
LIBOR plus										14.25%																										4.50%				2.00%
Loan bears interest ,description of variable rate basis			LIBOR plus 3%						0.5% LIBOR floor																											greater of 6%, or LIBOR plus 4.5%				LIBOR plus 2%														RE CDO holds a 5.52% interest in (i) a first priority mortgage loan collateralized by land located in Las Vegas, Nevada (the “Land”), which loan bears interest at LIBOR plus 40% with a current pay rate of 7.5% and the balance accruing and compounding and which had an outstanding balance of $21,227,000 at December 31, 2013, and (ii) a second priority mortgage loan collateralized by the Land which bears interest at 10% per annum, all of which accrues, and which had an outstanding balance of $30,401,000 at December 31, 2013. The interest in the loan was acquired for $1,093,000 and RE CDO accounts for this investment on the cost recovery method.
Notional amount of each Interest Rate Cap																																											50,000,000
Derivative Cost Of Interest Rate Cap																																											390,000
Interest rate cap, LIBOR																																				2.50%								4.00%	5.00%
Contribution for interest acquired in joint properties																			16,365,000
Percentage of interest in properties																			16.30%
Retained interest in the venture																			83.70%
Right to acquire interest in joint properties percentage																			50.00%
Revenue															9,488,000																								335,000		3,874,000
Loss from 1515 Market Street															3,805,000
Loss																																							474,000		2,097,000
Estimated development cost			1,625,000
Estimated development cost incurred			482,000
Number of residential parcels			4
Amount of purchase price paid in cash																															150,000
Percentage of non-controlling ownership interest	20.00%																				1.00%	22.00%	32.00%							1.00%
Net proceeds							4,922,000
Indirect future interest in Sullivan borrower																																																			76.00%	65.00%
Increase in indirect future interest in Sullivan Borrower																																																		6.00%	5.00%	11.00%
Investment by trust																																																	30,000,000																														3,935,000
Loans Receivable			101,100,000	211,250,000	114,333,000																																												56,150,000
Annual interest rate secured financing receivable			11.59%	11.43%																																																15.00%
Interest rate										8.25%																								11.00%		600.00%
Non-performing mortgage loan acquisition cost			21,437,000	163,800,000	67,619,000																																																																											6,625,000
Joint venture paid																																																																																1,137,000
Area of collateralized building																																																																																71,000
Lease expiration date																																																																																2014-09
Number of Automatic Extensions for building lease																																																																																6
Extension period for lease																																																																																5 years
Aggregate future funding commitments in joint venture																																																																										125,000,000
Reduction of future funding commitments																																																																										86,855,000
Distribution received																																				6,255,000
Gross proceeds from sales																20,500,000	1,850,000	3,300,000										12,000,000	2,500,000
Net proceeds																19,585,000	1,703,000											11,425,000	2,351,000
Gain or loss on sale of property																6,745,000	0	1,428,000										2,775,000	58,000
Net proceeds			38,690,000	7,024,000	3,629,000													3,202,000
Aggregate investment			149,085,000	134,859,000	162,142,000	0																																																992,000		1,779,000	1,296,000								11,000		10,845,000														0
Operating lease agreement amended date																																	Jul. 29, 2013
Area of office property																																200,000
Initial lease expiration date																																	Oct. 31, 2013
Number of extension periods																																	2
Lease extension term under renewal option																																	5 years
New lease extension term under renewal options one																																	5 years
New lease extension term under renewal options two																																	10 years
New lease extended date																																	Oct. 31, 2023
Lease period description																																	The new lease extends the term through October 31, 2023 with one ten-year or two five-year renewal options
Annual rents under the amended lease																																2,016,000															1,802,000	2,002,000
Principal amount of the loan												20,500,000
Office building area, square foot									260,000
Pari passu participation interest in the loan											50.00%
Mortgage loan, LIBOR floor rate									0.50%
Origination Fee (Amount)												205,000
Proceeds from sale of participation interest in loan								10,250,000
Credit allowed to borrower											100,000
Gain or loss recognized on the sale of the interest										0
Purchase price of acquired entity																																																																									9,000,000
Percentage of space of retail property leased																																																																									100.00%
Business acquisition cost of acquired entity face value																																																																									10,000,000
Loan Paid Off																				2,250,000					8,583,000	5,200,000	3,000,000
Aggregate Principle Payments																																																																								35,863,000
Pay Downs Of Recourse Debt																																																																								23,770,000
Proceeds from mortgage loans payable			198,100,000	36,897,000	32,494,000																																																2,750,000
Tranche subordinated interests																																																							6,240,000
Trust received distributions																																																							4,416,000
Assets held for sale carrying value			23,038,000																																																				2,500,000
Sale of interest																																																											25,000
Equity interest percentage																																																											17.00%
Percentage of Trust Hold interest rate																																																												49.67%
Loan held by this venture																																																																		40,000,000
Acquisition of loan																																																																32,500,000
Equity income distribution			24,112,000	21,593,000	12,696,000																																																							1,020,000	1,715,000			13,333,000
Equity income recorded																																																																2,676,000
Distribution received due to loan payoff		6,470,000
Common stock maximum number of shares available for sale																																																																						1,250,000	3,000,716
Aggregate purchase price																																																																						2,980,000	12,891,000
Net proceeds from sale of common stock shares																																																																						$ 3,626,000	$ 16,292,000