CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income (loss)	$ 89,083,552	$ 72,473,867	$ (25,579,651)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	46,109,794	67,755,152	69,513,484
Amortization of deferred financing costs	1,056,249	1,839,952	1,723,186
Amortization of stock-based compensation	84,866	85,486	76,285
Change in value of restricted common stock to Advisor	0	0	312,353
Amortization of loan premiums and discounts	(270,792)	(1,129,960)	(1,243,385)
Change in fair value of interest rate cap agreements	157,268	604,545	(61,698)
Loss on debt extinguishment	3,621,665	2,380,051	4,932,369
Gain on sales of real estate	(118,215,618)	(96,573,171)	0
Insurance claim recoveries	(1,394)	(352,497)	(993,527)
Loss on disposal of buildings and improvements	25,892	147,085	892,396
Unrealized gain on short-term investments	0	(278,883)	(84,750)
Equity in loss of unconsolidated joint venture	(3,339,202)	(663,896)	0
Changes in operating assets and liabilities:
Rents and other receivables	945,919	(333,347)	(8,509)
Other assets	626,178	960,983	(250,396)
Accounts payable and accrued liabilities	(461,309)	(3,106,834)	5,246,172
Due to affiliates	969,963	(1,372,025)	267,009
Net cash provided by operating activities	27,071,435	43,764,300	54,741,338
Cash Flows from Investing Activities:
Short-term investments	0	30,363,633	(30,000,000)
Cash contributions to unconsolidated joint venture	(3,435,411)	(3,854,197)	0
Cash distributions from unconsolidated joint venture	530,100	0	0
Acquisition of real estate investments	(67,886,062)	0	0
Additions to real estate investments	(9,564,647)	(16,401,961)	(28,268,601)
Escrow deposits for pending real estate acquisitions	(2,600,000)	0	0
Purchase of interest rate cap agreements	(223,300)	(37,350)	(259,000)
Proceeds from sales of real estate, net	310,434,652	124,918,577	0
Proceeds from insurance claims	1,394	352,497	993,527
Net cash provided by (used in) investing activities	227,256,726	135,341,199	(57,534,074)
Cash Flows from Financing Activities:
Proceeds from issuance of mortgage notes payable	106,482,000	17,638,751	428,196,350
Principal payments on mortgage notes payable	(239,272,864)	(22,745,424)	(557,964,896)
Borrowings from credit facilities	0	0	251,124,750
Principal payments on credit facilities	(38,410,500)	0	(16,000,000)
Payment of deferred financing costs	(1,323,128)	(310,819)	(5,489,473)
Payment of debt extinguishment costs	(2,572,386)	0	(3,202,337)
Distributions to common stockholders	(122,134,848)	(54,369,877)	(54,871,173)
Repurchases of common stock	(8,000,000)	(8,000,000)	(5,000,000)
Net cash (used in) provided by financing activities	(305,231,726)	(67,787,369)	36,793,221
Net (decrease) increase in cash, cash equivalents and restricted cash	(50,903,565)	111,318,130	34,000,485
Cash, cash equivalents and restricted cash, beginning of year	205,096,008	93,777,878	59,777,393
Cash, cash equivalents and restricted cash, end of year	154,192,443	205,096,008	93,777,878
Supplemental Disclosure of Cash Flow Information:
Interest paid, net of amounts capitalized of $0, $0 and $80,166 for the years ended December 31, 2018, 2017 and 2016, respectively	32,461,746	43,477,719	39,622,084
Supplemental Disclosure of Noncash Transactions:
Decrease in distributions payable	(1,079,991)	(30,054)	(42,906)
Assumption of mortgage notes payable to acquire real estate	65,000,000	0	0
Application of escrow deposits to acquire real estate	2,600,000	0	0
Increase in redeemable common stock payable	0	0	1,000,000
Non-cash contribution to unconsolidated joint venture	0	(3,281,298)	0
Mortgage notes payable assumed by buyer in connection with property sales	(67,140,194)	0	0
Assets and liabilities deconsolidated in connection with property sales:
Real estate, net	(98,350,076)	(382,696,431)	0
Notes payable, net	76,336,778	337,214,942	0
Restricted cash	(913,408)	(7,699,698)	0
Rents and other receivables	0	(346,067)	0
Accounts payable and accrued liabilities	674,912	11,330,808	0
(Decrease) increase in accounts payable and accrued liabilities from additions to investment in unconsolidated joint venture	(398,817)	398,817	0
Increase (decrease) in accounts payable and accrued liabilities from additions to real estate investments	346,169	(607,801)	378,711
Decrease in due to affiliates from additions to real estate investments	$ (3,924)	$ (15,037)	$ (161,652)