Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) (USD $)
 0 Months Ended 1 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 0 Months Ended
Sep. 30, 2014
Jun. 06, 2014
Mar. 31, 2011
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Sep. 30, 2014
Cantor Fitzgerald & Co [Member]
Sep. 30, 2014
Cantor Fitzgerald & Co [Member]
Sep. 30, 2014
Jefferies LLC [Member]
Sep. 30, 2014
Senior Common Stock [Member]
Mar. 31, 2011
Senior Common Stock [Member]
Sep. 30, 2014
Distribution Reinvestment Plan [Member]
Jun. 06, 2014
Public Offering [Member]
Class of Stock [Line Items]                          
Common stock, shares issued       17,907,652   15,662,414         3,500,000   1,610,000
Public offering price per share                         $ 17.00
Gross proceeds of initial public offering   $ 27,400,000                      
Net proceeds of initial public offering   26,000,000                      
Maximum aggregate sales price of shares to be issued under open market sale agreement             100,000,000 100,000,000 25,000,000        
Percentage of compensation of gross proceeds on sale of common stock               2.00%          
Number of shares sold under open market sale agreement             200,000 200,000          
Gross proceeds of shares sold under open market sale agreement             3,300,000            
Maximum remaining capacity to sell common stock under open market sale agreement             96,600,000 96,600,000          
Net proceeds under ATM program                 7,600,000        
Gross proceeds of shares sold under open market sale agreement                 21,800,000        
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 593,659                        
Senior common stock ongoing offering, gross proceeds       $ 42,636,000 $ 62,139,000         $ 8,900,000      
Shares of senior common stock issued       659,537   374,484           18,479