Equity Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Sealy [Member]	Dec. 31, 2011 Sealy [Member]	Dec. 31, 2010 Sealy [Member]	Dec. 31, 2012 Vintage Housing LLC [Member]	Dec. 31, 2011 Vintage Housing LLC [Member]	Dec. 31, 2012 Vintage Housing LLC [Member] VHH LLC [Member]	Dec. 31, 2011 Vintage Housing LLC [Member] VHH LLC [Member]	Dec. 31, 2012 WRT-Elad One South State Equity LP [Member]	Dec. 31, 2012 WRT-Elad One South State Equity LP [Member] Elad Canada Ltd [Member]	Dec. 31, 2012 WRT-Elad One South State Lender LP [Member]	Dec. 31, 2011 WRT-Elad One South State Lender LP [Member]	Dec. 31, 2012 WRT-Elad One South State Lender LP [Member] Elad Canada Ltd [Member]	Dec. 31, 2011 WRT-Elad One South State Lender LP [Member] Elad Canada Ltd [Member]	Dec. 31, 2012 WRT-Stamford LLC [Member]	Dec. 31, 2012 WRT-Stamford LLC [Member] Mack-Cali [Member]	Dec. 31, 2012 10 Metrotech Loan LLC [Member]	Dec. 31, 2012 10 Metrotech Loan LLC [Member] Atrium/Northstar [Member]	Dec. 31, 2012 RE CDO Management LLC [Member]	Dec. 31, 2011 RE CDO Management LLC [Member]	Dec. 31, 2012 RE CDO Management LLC [Member] Atrium Holding [Member]	Dec. 31, 2011 RE CDO Management LLC [Member] Atrium Holding [Member]	Dec. 31, 2012 Mentor Retail LLC [Member]	Dec. 31, 2012 Mentor Retail LLC [Member] Freed [Member]	Apr. 30, 2012 Concord Debt Holdings LLC [Member]	Dec. 31, 2012 Concord Debt Holdings LLC [Member] Inland/Lexington [Member]	Dec. 31, 2012 Concord Debt Holdings LLC [Member] Inland [Member]	Apr. 18, 2012 CDH CDO LLC [Member]	Dec. 31, 2012 CDH CDO LLC [Member] Inland/Lexington [Member]	Dec. 31, 2012 CDH CDO LLC [Member] Inland [Member]	Dec. 31, 2012 Northwest Atlanta Partners LP [Member] Sealy [Member]	Dec. 31, 2011 Northwest Atlanta Partners LP [Member] Sealy [Member]	Dec. 31, 2012 New Market GP LLC [Member] Sealy [Member]	Dec. 31, 2011 New Market GP LLC [Member] Sealy [Member]	Dec. 31, 2012 Airpark Nashville GP [Member]	Dec. 31, 2012 Airpark Nashville GP [Member] Sealy [Member]	Dec. 31, 2012 Brooks Building LLC [Member] Marc Realty [Member]	Dec. 31, 2011 Brooks Building LLC [Member] Marc Realty [Member]	Dec. 31, 2012 High Point Plaza LLC [Member] Marc Realty [Member]	Dec. 31, 2011 High Point Plaza LLC [Member] Marc Realty [Member]	Dec. 31, 2012 1701 Woodfield LLC [Member] Marc Realty [Member]	Dec. 31, 2011 1701 Woodfield LLC [Member] Marc Realty [Member]	Dec. 31, 2012 Enterprise Center LLC [Member] Marc Realty [Member]	Dec. 31, 2011 Enterprise Center LLC [Member] Marc Realty [Member]	Dec. 31, 2012 Michigan 30 LLC [Member] Marc Realty [Member]	Dec. 31, 2011 Michigan 30 LLC [Member] Marc Realty [Member]	Dec. 31, 2012 Salt Creek LLC [Member] Marc Realty [Member]	Dec. 31, 2011 Salt Creek LLC [Member] Marc Realty [Member]	Dec. 31, 2012 River Road LLC [Member] Marc Realty [Member]	May 31, 2012 River Road LLC [Member] Marc Realty [Member]	Dec. 31, 2011 River Road LLC [Member] Marc Realty [Member]	Dec. 31, 2011 3701 Algonquin Road LLC [Member]	Dec. 31, 2012 3701 Algonquin Road LLC [Member] Marc Realty [Member]	Dec. 31, 2011 900 Ridgebrook LLC [Member]	Dec. 31, 2012 900 Ridgebrook LLC [Member] Marc Realty [Member]	May 31, 2012 900 Ridgebrook LLC [Member] Marc Realty [Member]	Dec. 31, 2011 WRT - ROIC Lakeside Eagle LLC [Member]	Dec. 31, 2012 WRT - ROIC Lakeside Eagle LLC [Member] ROIC [Member]	Dec. 31, 2011 WRT - ROIC Lakeside Eagle LLC [Member] ROIC [Member]	Dec. 31, 2011 WRT - ROIC Riverside LLC [Member]	Dec. 31, 2010 WRT - ROIC Riverside LLC [Member]	Dec. 31, 2012 WRT - ROIC Riverside LLC [Member] ROIC [Member]	Dec. 31, 2011 WRT - ROIC Riverside LLC [Member] ROIC [Member]	Dec. 31, 2012 SoCal Office Portfolio Loan LLC [Member]	Dec. 31, 2011 SoCal Office Portfolio Loan LLC [Member]	Dec. 31, 2012 SoCal Office Portfolio Loan LLC [Member] New Valley/Starwood [Member]	Dec. 31, 2011 SoCal Office Portfolio Loan LLC [Member] New Valley/Starwood [Member]	Dec. 31, 2011 FII Co Invest LLC [Member]	Dec. 31, 2012 FII Co Invest LLC [Member] Broadway Partners [Member]	Dec. 31, 2011 FII Co Invest LLC [Member] Broadway Partners [Member]	Dec. 31, 2012 701 7th WRT Investors LLC [Member]	Dec. 31, 2012 701 7th WRT Investors LLC [Member] New Valley/Witkoff [Member]	Dec. 31, 2012 WRT-Fenway Wateridge LLC [Member]	Dec. 31, 2012 WRT-Fenway Wateridge LLC [Member] Fenway [Member]
Trust's carrying amounts in its equity investments
Nominal % Ownership									75.00%			50.00%			50.00%			20.00%		33.30%			50.00%			49.90%	33.33%	33.30%	33.30%	33.33%	33.30%	33.30%	60.00%		68.00%		50.00%	50.00%	50.00%		50.00%		50.00%		50.00%															50.00%				50.00%				73.00%			27.90%			60.90%	50.00%	50.00%
Equity investments	$ 134,859	$ 162,142	$ 81,937	$ 8,104	$ 11,348	$ 11,904	$ 30,534	$ 29,887	$ 30,534	$ 29,887	$ 460	$ 460	$ 24,644	$ 10,150	$ 24,644	$ 10,150	$ 8,501	$ 8,501	$ 10,845	$ 10,845	$ 1,779	$ 1,296	$ 1,779	$ 1,296	$ 551	$ 551			$ 3,974			$ 322	$ 8,104	$ 8,537		$ 2,811			$ 7,983	$ 7,679	$ 2,241	$ 2,441	$ 1,977	$ 2,047	$ 2,679	$ 2,679		$ 10,049				$ 1,000	$ 1,000	$ 250		$ 1,000		$ 1,100	$ 7		$ 7	$ 7,883	$ 7,883		$ 7,883	$ 8	$ 72,626	$ 8	$ 72,626	$ 1,800		$ 1,800	$ 28,735	$ 28,735	$ 1,522	$ 1,522