Related Party Transactions and Investments in Non-Consolidated Entities (Details 2) (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Balance Sheet Data (unaudited):
Real estate, net	$ 763,264,000		$ 767,938,000
Other assets	99,666,000		105,218,000
Total Liabilities	(253,077,000)		(256,612,000)
Total stockholders' equity	609,853,000		616,544,000
Operating Data (unaudited):
Rental revenues	54,495,000	46,001,000
Other revenues	33,000	98,000
Operating and maintenance expenses	(26,935,000)	(25,797,000)
Selling, general and administrative	(789,000)
Depreciation and amortization	(16,426,000)	(12,749,000)
Interest expense	(9,234,000)	(4,576,000)
Net income	1,144,000	2,977,000
Syndication, development and transaction fees from non-consolidated entities	6,866,000	1,561,000
Asset management fees, low end of range (as a percent)	1.00%
Asset management fees, high end of range (as a percent)	5.00%
Notice period for cancellation of applicable contracts (in days)	30
Asset management fee income from non-consolidated entities	$ 464,000	$ 397,000