Loans Receivable (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Summary of Trust's Loans Receivable
Loans receivable, net	$ 123,872	$ 114,333
160 Spear (6) [Member] | B Note [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	9.75%
Loans receivable, net		11,555
160 Spear (6) [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	15.00%
Loans receivable, net		4,846
Magazine (6) [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Loans receivable, net		18,805
Mortgage Loans Receivable Basis Spread on Variable Rate	1.23%
Mentor Building [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	10.00%
Loans receivable, net	2,511
Maturity date of loan	Sep. 10, 2017
Hotel Wales [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Loans receivable, net	20,097	20,101
Maturity date of loan	Oct. 05, 2013
Mortgage Loans Receivable Basis Spread on Variable Rate	4.00%
Renaissance Walk [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Loans receivable, net	3,000	3,000
Maturity date of loan	Jan. 01, 2014
Mortgage Loans Receivable Basis Spread on Variable Rate	12.00%
Legacy Orchard [Member] | Corporate Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	15.00%
Loans receivable, net	9,750	9,750
Maturity date of loan	Oct. 31, 2014
San Marbeya [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	5.88%
Loans receivable, net	26,816	26,501
Maturity date of loan	Jan. 01, 2015
Rockwell [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	12.00%
Loans receivable, net	294	275
Maturity date of loan	May 01, 2016
29 East Madison [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	8.00%
Loans receivable, net	365	4,028
Maturity date of loan	May 31, 2016
500-512 7th Avenue [Member] | B Note [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	7.19%
Loans receivable, net	9,990	9,979
Maturity date of loan	Jul. 11, 2016
180 N. Michigan [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Loans receivable, net		2,930
Wellington Tower [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	6.79%
Loans receivable, net	2,622	2,563
Maturity date of loan	Jul. 11, 2017
Broward Financial Center [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	9.84%
Loans receivable, net	30,139
Maturity date of loan	Oct. 15, 2012
Fenway Shea (1) [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	12.00%
Loans receivable, net	2,250
Maturity date of loan	Apr. 05, 2014
127 West 25th Street [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	14.00%
Loans receivable, net	9,105
Maturity date of loan	Apr. 30, 2015
Marc Realty - 30 N Michigan (1) [Member] | Mezzanine [Member]
Summary of Trust's Loans Receivable
Interest rate on mortgage loans	10.00%
Loans receivable, net	6,607
Maturity date of loan	May 31, 2015
Churchill (1) [Member] | Whole Loan [Member]
Summary of Trust's Loans Receivable
Loans receivable, net	$ 326
Maturity date of loan	Jun. 01, 2015
Mortgage Loans Receivable Basis Spread on Variable Rate	3.75%