Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues	$ 35,657	$ 45,577	$ 51,147
Gain on sale of real estate	0	1,044	0
Excess tax benefit of stock-based compensation	107	0	0
Aggregated distributions received from equity method investees	10,314
Distribution of earnings from unconsolidated joint ventures	7,200	4,500	7,200
Distribution of equity from unconsolidated joint ventures	3,114	1,600	$ 1,100
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues	475	710
Gain on sale of real estate	411	615
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09 | Pro Forma
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues	73	1,112
Gain on sale of real estate	$ 9	$ 1,017