Quarterly report pursuant to Section 13 or 15(d)

Mandatorily-Redeemable Preferred Stock (Detail)

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Mandatorily-Redeemable Preferred Stock (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended
Aug. 17, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]        
Common stock, shares issued (in shares)   13,485,025   10,024,875
Proceeds from issuance of preferred stock $ 28,800 $ 0 $ 28,750  
Proceeds from issuance of equity   $ 40,421 360  
Redemption price (in dollars per share)   $ 25.93    
Offering costs   $ 1,962 $ 242  
Fair value of preferred stock   $ 29,800    
Series A Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Number of shares issued (in shares) 1,000,000      
Dividend rate (as percent) 6.375%      
Par value (in dollars per share) $ 0.001      
Average sales price price (in dollars per share) $ 25      
Proceeds from issuance of equity $ 27,600      
Redemption price (in dollars per share) $ 25      
Offering costs $ 1,200      
Series A Preferred Stock | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   $ 1.1953125 $ 0.190364583  
Series A Preferred Stock | January 31, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | February 28, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | March 31, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | April 28, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | May 31, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | June 30, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | July 31, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | August 31, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   0.1328125    
Series A Preferred Stock | September 29, 2017 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)   $ 0.1328125    
Series A Preferred Stock | September 30, 2016 | Preferred Stock        
Subsidiary, Sale of Stock [Line Items]        
Distributions per share (in dollars per share)     $ 0.190364583  
Series A Preferred Stock | Over-allotment option        
Subsidiary, Sale of Stock [Line Items]        
Number of shares issued (in shares) 150,000