Equity Investments - Summarized Statements of Operations of Real Estate Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Expenses
General and administrative	$ 1,098	$ 782	$ 1,945	$ 1,665
Real estate taxes	1,659	884	2,542	2,003
Other income:
Total other income (loss)	3,045	44	12,802	5,691
Vintage Housing LLC [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total revenue	10,824	11,448	21,403	20,600
Expenses
Operating	4,486	4,292	9,303	7,996
Real estate taxes	113	134	269	303
Interest	542	1,651	995	3,321
Depreciation and amortization	244	3,324	691	5,627
Other expenses	1,371	1,544	2,723	2,725
Total expenses	6,756	10,945	13,981	19,972
Net income	4,068	503	7,422	628
Other income:
Loss attributable to non-controlling interests	745	358	723	762
Net income	4,813	861	8,145	1,390
Trust's share of net income	2,696	595	4,617	934
RE CDO Management LLC [Member]
Expenses
General and administrative	59	87	117	194
Other expenses	13	33	1,432	65
Total expenses	72	120	1,549	259
Other income:
Gain on sale of investment			8,940
Other income	55	152	131	313
Total other income (loss)	55	152	9,071	313
Net income	(17)	32	7,522	54
Trust's share of net income	$ (9)	$ 17	$ 3,761	$ 28