Summary of Related Party Costs (Detail) - USD ($)
 9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Related Party Transaction [Line Items]    
Related party costs, Incurred $ 10,599,794 $ 48,646,868
Related party costs, Paid 10,862,194 45,677,116
Related party costs, Payable 2,915,835 3,178,235
Operating expenses (including organizational costs)    
Related Party Transaction [Line Items]    
Related party costs, Incurred 589,299 735,891
Related party costs, Paid 472,214 777,354
Related party costs, Payable 123,593 6,508
Asset management fees    
Related Party Transaction [Line Items]    
Related party costs, Incurred 3,978,872 2,970,846
Related party costs, Paid 3,978,872 2,970,846
Related party costs, Payable 0 0
Property management fees    
Related Party Transaction [Line Items]    
Related party costs, Incurred [1] 4,166,598 2,752,862
Related party costs, Paid [1] 4,166,598 2,752,862
Related party costs, Payable [1] 0 0
Acquisition expenses    
Related Party Transaction [Line Items]    
Related party costs, Incurred 212,577 10,729,535
Related party costs, Paid 212,577 10,729,535
Related party costs, Payable 0 0
Selling commissions    
Related Party Transaction [Line Items]    
Related party costs, Incurred 966,516 21,141,748
Related party costs, Paid 966,516 21,141,748
Related party costs, Payable 0 0
Dealer manager fee    
Related Party Transaction [Line Items]    
Related party costs, Incurred 353,167 6,573,962
Related party costs, Paid 513,881 6,573,760
Related party costs, Payable 0 160,714
Stockholder servicing fee    
Related Party Transaction [Line Items]    
Related party costs, Incurred [2] 299,299 3,297,305
Related party costs, Paid [2] 518,070 286,292
Related party costs, Payable [2] 2,792,242 3,011,013
Offering costs    
Related Party Transaction [Line Items]    
Related party costs, Incurred 33,466 444,719
Related party costs, Paid 33,466 444,719
Related party costs, Payable $ 0 $ 0
[1] During the nine months ended September 30, 2017 and year ended December 31, 2016, property management fees included approximately $3.2 million and $2.2 million, respectively, of fees paid to the sub-property manager of our properties. This includes the costs incurred related to the change in property management of approximately $0.8 million.
[2] We pay our Dealer Manager an ongoing stockholder servicing fee that is payable monthly and accrues daily in an amount equal to 1/365th of 1% of the purchase price per share of the Class T Shares sold in the Primary Offering.