Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) (USD $)
 0 Months Ended 1 Months Ended 12 Months Ended
Dec. 26, 2013
Jul. 11, 2013
Apr. 29, 2013
Mar. 31, 2011
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2013
Senior Common Stock [Member]
Mar. 31, 2011
Senior Common Stock [Member]
Nov. 25, 2013
Public Offering [Member]
Jun. 24, 2013
Public Offering [Member]
Apr. 29, 2013
Public Offering [Member]
Dividends Payable [Line Items]                        
Capital gains         0.00% 0.00% 0.00%          
Common stock, shares issued         15,662,414 11,083,584     3,500,000 1,377,500 1,320,000 1,265,000
Public offering price per share                   $ 18.15 $ 18.82 $ 18.90
Gross proceeds of initial public offering $ 25,500,000 $ 27,800,000 $ 23,900,000                  
Net proceeds of initial public offering 24,200,000 26,300,000 22,600,000                  
Underwriters' option to purchase additional shares of common stock 26,422 158,000                    
Maximum aggregate sales price of shares to be issued under open market sale agreement         25,000,000              
Gross proceeds under ATM program         7,800,000              
Number of shares sold under open market sale agreement         762,478              
Net proceeds of shares sold under open market sale agreement         14,000,000              
Maximum remaining capacity to sell common stock under open market sale agreement         11,000,000              
Common stock, par value         $ 0.001 $ 0.001     $ 0.001      
Common stock shares issued, selling price                 $ 15.00      
Shares intended to be offered pursuant to primary offering       3,000,000                
Shares intended to be offered pursuant to senior common distribution reinvestment plan       500,000                
Shares of senior common stock sold in ongoing offering               307,979        
Senior common stock ongoing offering, gross proceeds         $ 88,121,000 $ 4,191,000 $ 39,707,000 $ 4,600,000        
Shares of senior common stock issued               10,223