Agreements and Transactions with Related Parties - Related Party Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Amounts Included in the Consolidated Statements of Operations
Available Cash Distributions	$ 2,186	$ 2,380	$ 3,861	$ 3,657
Personnel and overhead reimbursements	787	740	1,569	1,609
Interest expense on deferred acquisition fees, interfund loan, and accretion of interest on annual distribution and shareholder servicing fee	319	188	620	428
Director compensation	53	53	105	105
Acquisition expenses	(7)	2,816	45	4,711
Operating expenses	6,112	8,151	11,631	14,160
Acquisition Fees Capitalized
Personnel and overhead reimbursements	2	73	184	248
Current acquisition fees	0	452	1,393	1,821
Deferred acquisition fees	0	362	1,114	1,457
Transaction fees incurred	2	887	2,691	3,526
Related Party
Amounts Included in the Consolidated Statements of Operations
Asset management fees	2,767	2,468	5,476	4,877
Acquisition expenses	$ 0	$ 2,322	$ 0	$ 3,484