Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) Property	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Property Segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Nov. 15, 2017
Summary of Significant Accounting Policies [Line Items]
Beneficial interest for ownership percentage			2.60%
Number of properties acquired | Property	4		4
Capitalized acquisition-related transaction costs	$ 3,400,000		$ 3,400,000
Business acquisition, transaction costs	$ 100,000	$ 1,200,000	$ 500,000	$ 2,600,000
Initial term of lease	12 months		12 months
Days allowed for lease cancellation			30 days
Estimated amortization expenses of intangible assets in 2018	$ 2,200,000		$ 2,200,000
Estimated amortization expenses of intangible assets in 2019	8,700,000		8,700,000
Estimated amortization expenses of intangible assets in 2020	2,500,000		2,500,000
Debt issuance costs	$ 2,345,183		$ 2,345,183		$ 700,362
Offering cost as percentage of gross offering proceeds	1.00%		1.00%
Maximum period for reimbursement of offering cost			60 days
Maximum offering cost rate			3.50%
Maximum Dealer Manager sales commission as percentage of gross offering proceeds	6.00%		6.00%
Maximum Dealer Manager fee as percentage of gross offering proceeds	3.00%		3.00%			2.00%
Underwriting compensation			10.00%
Minimum percentage of ordinary taxable income to be distributed to stockholders			90.00%
Number of reportable segments | Segment			2
Class A Common Stock [Member]
Summary of Significant Accounting Policies [Line Items]
Maximum Dealer Manager sales commission as percentage of gross offering proceeds	6.00%		6.00%
Maximum Dealer Manager fee as percentage of gross offering proceeds	3.00%		3.00%
Class T Common Stock [Member]
Summary of Significant Accounting Policies [Line Items]
Maximum Dealer Manager sales commission as percentage of gross offering proceeds	3.00%		3.00%
Maximum Dealer Manager fee as percentage of gross offering proceeds	3.00%		3.00%
Daily stockholder servicing fee accrual description			1/365th of 1% of the purchase price per share
Class W Common Stock [Member]
Summary of Significant Accounting Policies [Line Items]
Maximum Dealer Manager fee as percentage of gross offering proceeds	9.00%		9.00%
Daily stockholder servicing fee accrual description			1/365th of 0.5% of the purchase price per share
Minimum [Member] | Furniture, Fixtures and Equipment [Member]
Summary of Significant Accounting Policies [Line Items]
Standard depreciable life			3 years
Maximum [Member] | Furniture, Fixtures and Equipment [Member]
Summary of Significant Accounting Policies [Line Items]
Standard depreciable life			7 years
In-Place Leases [Member]
Summary of Significant Accounting Policies [Line Items]
Payments to acquire intangible assets			$ 16,000,000		6,300,000
Gross amount of lease intangibles	$ 22,300,000		22,300,000		6,200,000
Accumulated amortization of lease intangibles	$ 8,900,000		$ 8,900,000		$ 2,500,000