Annual report pursuant to Section 13 and 15(d)

Mandatorily-Redeemable Preferred Stock (Detail)

v3.6.0.2
Mandatorily-Redeemable Preferred Stock (Detail) - USD ($)
 12 Months Ended
Aug. 17, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Subsidiary, Sale of Stock [Line Items]        
Proceeds from issuance of mandatorily-redeemable preferred stock   $ 28,750,000 $ 0 $ 0
Proceeds from issuance of equity   $ 360,472 23,132,910 15,024,003
Redemption price of redeemable preferred stock (in dollars per share)   $ 25.44    
Payments of legal costs   $ 271,791 $ 1,482,029 $ 950,965
Term preferred stock, fair value   $ 29,300,000    
Series A cumulative term preferred stock        
Subsidiary, Sale of Stock [Line Items]        
Number of shares issued (in shares) 1,000,000 1,150,000    
Preferred stock, dividend rate (as percent) 6.375%      
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001 $ 0.001  
Public offering price (in dollars per share) $ 25      
Proceeds from issuance of equity $ 27,600,000      
Redemption price of redeemable preferred stock (in dollars per share) $ 25      
Payments of legal costs $ 1,200,000      
Series A cumulative term preferred stock | Over-Allotment Option        
Subsidiary, Sale of Stock [Line Items]        
Number of shares issued (in shares) 150,000