Equity Investments - Trust's Carrying Amounts in Its Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Sealy [Member]	Dec. 31, 2012 Sealy [Member]	Jun. 30, 2013 Vintage Housing LLC [Member]	Dec. 31, 2012 Vintage Housing LLC [Member]	Jun. 30, 2013 Vintage Housing LLC [Member] VHH LLC [Member]	Dec. 31, 2012 Vintage Housing LLC [Member] VHH LLC [Member]	Dec. 31, 2012 WRT-Elad One South State Equity LP [Member]	Jun. 30, 2013 WRT-Elad One South State Equity LP [Member] Elad Canada Ltd [Member]	Dec. 31, 2012 WRT-Elad One South State Equity LP [Member] Elad Canada Ltd [Member]	Jun. 30, 2013 WRT-Elad One South State Lender LP [Member]	Dec. 31, 2012 WRT-Elad One South State Lender LP [Member]	Jun. 30, 2013 WRT-Elad One South State Lender LP [Member] Elad Canada Ltd [Member]	Dec. 31, 2012 WRT-Elad One South State Lender LP [Member] Elad Canada Ltd [Member]	Jun. 30, 2013 WRT-Stamford [Member]	Dec. 31, 2012 WRT-Stamford [Member]	Jun. 30, 2013 WRT-Stamford [Member] Mack-Cali [Member]	Dec. 31, 2012 WRT-Stamford [Member] Mack-Cali [Member]	Jun. 30, 2013 10 Metrotech Loan LLC [Member]	Dec. 31, 2012 10 Metrotech Loan LLC [Member]	Jun. 30, 2013 10 Metrotech Loan LLC [Member] Atrium/Northstar [Member]	Dec. 31, 2012 10 Metrotech Loan LLC [Member] Atrium/Northstar [Member]	Jun. 30, 2013 RE CDO Management LLC [Member]	Dec. 31, 2012 RE CDO Management LLC [Member]	Jun. 30, 2013 RE CDO Management LLC [Member] Atrium Holding [Member]	Dec. 31, 2012 RE CDO Management LLC [Member] Atrium Holding [Member]	Jun. 30, 2013 Mentor Retail LLC [Member]	Dec. 31, 2012 Mentor Retail LLC [Member]	Jun. 30, 2013 Mentor Retail LLC [Member] Freed [Member]	Dec. 31, 2012 Mentor Retail LLC [Member] Freed [Member]	Feb. 25, 2013 Concord Debt Holdings LLC [Member]	Jun. 30, 2013 Concord Debt Holdings LLC [Member] Inland [Member]	Dec. 31, 2012 Concord Debt Holdings LLC [Member] Inland [Member]	Jun. 30, 2013 CDH CDO LLC [Member] Inland [Member]	Dec. 31, 2012 CDH CDO LLC [Member] Inland [Member]	Jun. 30, 2013 Northwest Atlanta Partners LP [Member] Sealy [Member]	Dec. 31, 2012 Northwest Atlanta Partners LP [Member] Sealy [Member]	Jun. 30, 2013 New Market GP LLC [Member] Sealy [Member]	Jun. 30, 2013 Airpark Nashville GP [Member] Sealy [Member]	Jun. 30, 2013 Brooks Building LLC [Member] Marc Realty [Member]	Dec. 31, 2012 Brooks Building LLC [Member] Marc Realty [Member]	Jun. 30, 2013 High Point Plaza LLC [Member] Marc Realty [Member]	Dec. 31, 2012 High Point Plaza LLC [Member] Marc Realty [Member]	Jun. 30, 2013 1701 Woodfield LLC [Member] Marc Realty [Member]	Dec. 31, 2012 1701 Woodfield LLC [Member] Marc Realty [Member]	Jun. 30, 2013 Enterprise Center LLC [Member] Marc Realty [Member]	Dec. 31, 2012 Enterprise Center LLC [Member] Marc Realty [Member]	Jun. 30, 2013 Atrium Mall LLC [Member]	Jun. 30, 2013 Atrium Mall LLC [Member] Marc Realty [Member]	Jun. 30, 2013 WRT - ROIC Lakeside Eagle LLC [Member]	Jun. 30, 2013 WRT - ROIC Lakeside Eagle LLC [Member] ROIC [Member]	Dec. 31, 2012 SoCal Office Portfolio Loan [Member]	Jun. 30, 2013 SoCal Office Portfolio Loan [Member] New Valley/Starwood [Member]	Dec. 31, 2012 SoCal Office Portfolio Loan [Member] New Valley/Starwood [Member]	Jun. 30, 2013 701 7th WRT Investors LLC [Member]	Dec. 31, 2012 701 7th WRT Investors LLC [Member]	Jun. 30, 2013 701 7th WRT Investors LLC [Member] New Valley/Witkoff [Member]	Dec. 31, 2012 701 7th WRT Investors LLC [Member] New Valley/Witkoff [Member]	Jun. 30, 2013 WRT-Fenway Wateridge LLC [Member]	Dec. 31, 2012 WRT-Fenway Wateridge LLC [Member]	Jun. 30, 2013 WRT-Fenway Wateridge LLC [Member] Fenway [Member]	Dec. 31, 2012 WRT-Fenway Wateridge LLC [Member] Fenway [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Nominal % Ownership							75.00%			50.00%				50.00%				20.00%		33.33%		33.30%				50.00%				49.90%		17.00%	33.30%		24.80%		60.00%		68.00%	50.00%	50.00%		50.00%		50.00%		50.00%			50.00%		50.00%		73.00%				60.90%				50.00%
Equity investments	$ 141,645	$ 134,859	$ 7,871	$ 8,104	$ 32,886	$ 30,534		$ 30,534	$ 460		$ 460	$ 23,614	$ 24,644	$ 23,614	$ 24,644	$ 8,773	$ 8,501	$ 8,773	$ 8,501	$ 10,845	$ 10,845	$ 10,845	$ 10,845	$ 1,061	$ 1,779	$ 1,061	$ 1,779	$ 584	$ 551	$ 584	$ 551		$ 3,932	$ 3,974	$ 1,079	$ 322	$ 7,871	$ 8,104			$ 8,049	$ 7,983	$ 2,175	$ 2,241	$ 2,036	$ 1,977	$ 2,471	$ 2,679	$ 3,935	$ 3,935	$ 10	$ 10	$ 8		$ 8	$ 30,602	$ 28,735	$ 30,602	$ 28,735	$ 1,722	$ 1,522	$ 1,722	$ 1,522
Nominal % Ownership							75.00%			50.00%				50.00%				20.00%		33.33%		33.30%				50.00%				49.90%		17.00%	33.30%		24.80%		60.00%		68.00%	50.00%	50.00%		50.00%		50.00%		50.00%			50.00%		50.00%		73.00%				60.90%				50.00%
Equity investments	$ 141,645	$ 134,859	$ 7,871	$ 8,104	$ 32,886	$ 30,534		$ 30,534	$ 460		$ 460	$ 23,614	$ 24,644	$ 23,614	$ 24,644	$ 8,773	$ 8,501	$ 8,773	$ 8,501	$ 10,845	$ 10,845	$ 10,845	$ 10,845	$ 1,061	$ 1,779	$ 1,061	$ 1,779	$ 584	$ 551	$ 584	$ 551		$ 3,932	$ 3,974	$ 1,079	$ 322	$ 7,871	$ 8,104			$ 8,049	$ 7,983	$ 2,175	$ 2,241	$ 2,036	$ 1,977	$ 2,471	$ 2,679	$ 3,935	$ 3,935	$ 10	$ 10	$ 8		$ 8	$ 30,602	$ 28,735	$ 30,602	$ 28,735	$ 1,722	$ 1,522	$ 1,722	$ 1,522