Agreements and Transactions with Related Parties - Related Party Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Amounts Included in the Consolidated Statements of Income
Asset management fees	$ 2,874	$ 2,709
Available Cash Distributions	1,905	1,675
Personnel and overhead reimbursements	717	782
Interest expense on deferred acquisition fees, interfund loan, and accretion of interest on annual distribution and shareholder servicing fee	(62)	301
Director compensation	40	53
Operating expenses	5,474	5,520
Advisor Fees Capitalized
Current acquisition fees	721	1,393
Deferred acquisition fees	577	1,114
Capitalized personnel and overhead reimbursements	112	182
Transaction fees incurred	$ 1,410	$ 2,689