Equity Investments - Summarized Balance Sheets of Real Estate Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 186,132	$ 97,682	$ 43,959	$ 40,952
TOTAL ASSETS	950,310	923,163
LIABILITIES AND MEMBERS' CAPITAL
TOTAL LIABILITIES AND EQUITY	950,310	923,163
Vintage Housing LLC [Member]
ASSETS
Real estate, net	351,320	340,666
Cash and cash equivalents	6,002	6,555
Receivables and other assets	78,468	68,559
TOTAL ASSETS	435,790	415,780
LIABILITIES AND MEMBERS' CAPITAL
Mortgage and notes payable	314,844	298,654
Other liabilities	50,963	53,687
Non-controlling interests	18,976	15,997
Members' Capital	51,007	47,442
TOTAL LIABILITIES AND EQUITY	435,790	415,780
Carrying value of the Trust's investment in Vintage Housing	32,886	30,534
RE CDO Management LLC [Member]
ASSETS
Cash and cash equivalents	156	123
Loan receivable	1,050	1,070
Receivables and other assets	933	2,400
TOTAL ASSETS	2,139	3,593
LIABILITIES AND MEMBERS' CAPITAL
Other liabilities	18	36
Members' Capital	2,121	3,557
TOTAL LIABILITIES AND EQUITY	2,139	3,593
Carrying value of the Trust's investment in Vintage Housing	$ 1,061	$ 1,779