Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Cash Flows from Operating Activities:
Net loss	$ (20,671,331)	$ (8,132,098)	$ (37,635,602)	$ (23,504,195)	$ (33,623,841)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	17,855,195	17,036,633	52,920,337	51,161,020
Loss on disposal of buildings and improvements			211,742	108,715
Amortization of deferred financing costs	269,417	257,111	762,658	766,801
Amortization of stock-based compensation			60,721	66,019
Change in fair value of interest rate cap agreements			(641,013)	438,261
Amortization of loan discount			207,074	266,238
Loss on debt extinguishment	4,975,497	0	4,975,497	0
Insurance claim recoveries			(331,716)	(341,250)
Changes in operating assets and liabilities:
Rents and other receivables			(136,231)	(17,315)
Other assets			(351,980)	186,555
Accounts payable and accrued liabilities			5,900,772	2,224,747
Due to affiliates			(206,276)	(1,173,002)
Net cash provided by operating activities			25,735,983	30,182,594
Cash Flows from Investing Activities:
Additions to real estate investments			(13,049,961)	(21,353,583)
Purchase of interest rate cap agreements			43,200	0
Proceeds from settlement of interest rate cap agreements			270,000	0
Proceeds from insurance claims			331,716	341,250
Net cash used in investing activities			(12,491,445)	(21,012,333)
Cash Flows from Financing Activities:
Proceeds from issuance of mortgage notes payable			160,850,000	0
Principal payments on mortgage notes payable			(611,223,676)	(199,316)
Borrowings from credit facilities			562,669,000	10,000,000
Principal payments on credit facilities			(56,000,000)	0
Payments of commissions on sale of common stock			(173,111)	(176,811)
Payment of deferred financing costs			(4,538,261)	0
Payment of debt extinguishment costs			(1,019,491)	0
Distributions to common stockholders	(5,941,991)	(5,561,473)	(17,364,466)	(16,302,516)
Repurchase of common stock			(6,886,216)	(3,952,041)
Net cash provided by (used in) financing activities			26,313,779	(10,630,684)
Net increase (decrease) in cash, cash equivalents and restricted cash			39,558,317	(1,460,423)
Cash, cash equivalents and restricted cash, beginning of the period			38,667,705	38,815,266	38,815,266
Cash, cash equivalents and restricted cash, end of the period	$ 78,226,022	$ 37,354,843	78,226,022	37,354,843	$ 38,667,705
Supplemental Disclosures of Cash Flow Information:
Interest paid			29,474,797	23,401,164
Supplemental Disclosures of Noncash Flow Transactions:
Decrease in distributions payable			(77,561)	(44,315)
Distributions paid to common stockholders through common stock issuances pursuant to the distribution reinvestment plan			17,175,364	17,546,003
(Decrease) increase in redeemable common stock			(36,397,062)	6,472,018
(Decrease) increase in redemptions payable			(631,040)	1,043,310
Decrease in accounts payable and accrued liabilities from additions to real estate investments			(1,590,676)	(1,498,767)
Decrease in due to affiliates from additions to real estate investments			(137,656)	(159,779)
Decrease in due to affiliates for commissions on sale of common stock			$ (205,525)	$ (176,811)