Agreements and Transactions with Related Parties (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Amounts included in the statement of income:
Asset management fees	$ 5,111	$ 4,553
Distributions of available cash	4,277	2,693
Personnel reimbursements	2,639	938
Office rent reimbursements	218	157
Operating Expenses	12,245	8,341
Transaction fees incurred:
Current acquisition fees	1,762	4,204
Deferred acquisition fees	1,183	3,433
Transaction Fees Incurred	2,945	7,637
Unpaid transaction fees:
Deferred acquisition fees	19,824		26,246
Subordinated disposition fees	202		202
Unpaid Transaction Fees	$ 20,026		$ 26,448