Subsequent Events - Additional Information (Detail) (USD $)	6 Months Ended			1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 10 Metrotech Loan LLC [Member]	Aug. 31, 2013 Subsequent Event [Member]	Aug. 01, 2013 Subsequent Event [Member]	Jul. 23, 2013 Subsequent Event [Member]	Jul. 02, 2013 Subsequent Event [Member]
Subsequent Event [Line Items]
Gross proceeds from sales of real estae							$ 1,850,000
Net proceeds received							1,703,000
Additional capital contribution						4,927,000
Committed to invest						120,000,000
Initial contribution of investment committed						35,404,000
Percentage of Excess of of the Thanksgiving Tower receivable				81.00%
Amount of Excess of of the Thanksgiving Tower receivable				16,725,000
Contingent purchase price				2,063,000
Loan paid off			40,000,000
Trust received distribution			13,333,000
Ownership interest in the venture			33.33%
Gross sale proceeds					3,300,000
Net proceeds	$ 31,312,000	$ 632,000			$ 3,202,000