Variable Interest Entities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) Property Owner	Dec. 31, 2016 USD ($) Property	Dec. 31, 2015 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Gain (Loss) on Sale of Properties | $	$ 17,753,303	$ 14,072,317	$ 4,599,109
Number of Variable Interest Entities | Property	23	20
Consolidated Properties [Member]
Accounts Notes And Loans Receivable [Line Items]
Gain (Loss) on Sale of Properties | $	$ 0	$ 0	$ 0
Total Owners [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of Owners | Owner	3
Related party owner [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of Owners | Owner	1