Related Party Arrangements - Narrative - Other Operating Expense Reimbursements (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) quarter	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Related Party Transaction [Line Items]
Other operating expense reimbursement, percentage of average invested assets, threshold	2.00%
Other operating expense reimbursement, percentage of net income, threshold	25.00%
Operating expenses	$ 167,781,723	$ 236,404,648	$ 243,817,183
Other Operating Expense Reimbursement [Member]
Related Party Transaction [Line Items]
General and administrative expenses	$ 6,269,238	6,732,330	9,039,171
Operating expenses, percent of average invested assets	0.10%
Operating expenses, percent of net loss	1.10%
Other Operating Expense Reimbursement [Member] | Advisor and its Affiliates [Member]
Related Party Transaction [Line Items]
Operating expenses	$ 988,367	1,244,264	1,232,493
Overhead expenses	896,144	1,045,532	772,576
Related party transaction, expenses from transactions with related party	$ 0	$ 0	$ 0
Advisor [Member] | Advisor [Member] | Other Operating Expense Reimbursement [Member]
Related Party Transaction [Line Items]
Operating expenses limited, number of quarters | quarter	4
Other operating expense reimbursement, percentage of average invested assets, threshold	2.00%
Other operating expense reimbursement, percentage of net income, threshold	25.00%
Average invested assets, calculation period	12 months