Equity Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 131,448	$ 97,682	$ 79,526	$ 40,952
TOTAL ASSETS	919,077	923,163
LIABILITIES AND MEMBERS' CAPITAL
TOTAL LIABILITIES AND EQUITY	919,077	923,163
Vintage Housing LLC [Member]
ASSETS
Real estate, net	343,907	340,666
Cash and cash equivalents	6,642	6,555
Receivables and other assets	71,365	68,559
TOTAL ASSETS	421,914	415,780
LIABILITIES AND MEMBERS' CAPITAL
Mortgage and notes payable	300,686	298,654
Other liabilities	54,572	53,687
Non-controlling interests	17,946	15,997
Members' Capital	48,710	47,442
TOTAL LIABILITIES AND EQUITY	421,914	415,780
Carrying value of the Trust's investment in Vintage Housing	$ 31,801	$ 30,534