Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

v3.5.0.2
Equity - Additional Information (Detail)
 9 Months Ended 12 Months Ended
Aug. 17, 2016
$ / shares
shares
Sep. 30, 2016
USD ($)
security
$ / shares
shares
Sep. 30, 2015
USD ($)
shares
Dec. 31, 2015
$ / shares
shares
Jun. 30, 2016
$ / shares
Aug. 07, 2015
USD ($)
Dec. 31, 2014
shares
Apr. 02, 2014
USD ($)
Subsidiary, Sale of Stock [Line Items]                
Common stock, shares authorized (in shares)   18,000,000   20,000,000        
Temporary equity, par or stated value per share (in dollars per share) | $ / shares   $ 0.001   $ 0.001        
Common stock, par value (in dollars per share) | $ / shares   $ 0.001   $ 0.001        
Common stock, shares issued (in shares)   10,024,875   9,992,941        
Common stock, shares outstanding (in shares)   10,024,875   9,992,941        
Company's ownership percent   89.20%   100.00%        
OP units held by non-controlling limited partners   1,215,306 0          
Proceeds from issuance of preferred stock | $   $ 28,750,000 $ 0          
At-the-Market Program [Member]                
Subsidiary, Sale of Stock [Line Items]                
Common stock, shares issued (in shares)   64,561            
Sale of common stock sold under sale agreement   31,934            
Average sales price of common stock sold (in dollars per share) | $ / shares         $ 11.29      
Gross proceeds from issuance of common stock | $   $ 360,472            
Net proceeds from issuance of common stock | $   $ 355,057            
Shares Issued, Price Per Share | $ / shares   $ 10.23            
Common stock, value, outstanding | $   $ 660,176            
Common stock, value, issued | $   $ 650,266            
Maximum [Member]                
Subsidiary, Sale of Stock [Line Items]                
Securities allowed for issuance | $               $ 300,000,000
Maximum [Member] | At-the-Market Program [Member]                
Subsidiary, Sale of Stock [Line Items]                
Common stock, value authorized | $           $ 30,000,000.0    
Common Stock [Member]                
Subsidiary, Sale of Stock [Line Items]                
Common stock, shares outstanding (in shares)   10,024,875   9,992,941     7,753,717  
Maximum Number Of Securities Can Be Sold Under Shelf Registration Statement | security   2            
Value of common stock issuable per registration statement | $   $ 23,600,000            
Number of shares issued (in shares)   31,934   2,239,224        
Common Stock [Member] | Universal Registration Statement [Member]                
Subsidiary, Sale of Stock [Line Items]                
Common stock, shares issued (in shares)   2,188,014            
Series A Preferred Stock [Member]                
Subsidiary, Sale of Stock [Line Items]                
Number of shares issued (in shares) 1,000,000 1,150,000            
Shares Issued, Price Per Share | $ / shares $ 25