Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 segment loan M entity	Sep. 30, 2010	Dec. 31, 2010
Summary of Significant Accounting Policies
Number of reportable segments			1
Original maturities of short-term investments, maximum (in months)			3
Maximum ownership percentage to classify investments as cost method investments (as a percent)			5.00%
Capitalized financing cost, net of amortization	$ 3,900,000		$ 3,900,000		$ 4,100,000
Amortization of financing costs included in interest expense	1,000,000	200,000	2,400,000	300,000
Penalty payable on prohibited transactions (as a percent)			100.00%
Number of taxable REIT subsidiaries (in entities)			2
Provision for income taxes related to TRS	$ (463,000)	$ 168,000	$ 741,000	$ 208,000
Federal income tax rate (as a percent)			34.00%	33.00%
State income tax rate (as a percent)			7.50%	7.50%