Quarterly report pursuant to Section 13 or 15(d)

Stockholder's Equity (Details)

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Stockholder's Equity (Details) - USD ($)
 3 Months Ended 25 Months Ended
Mar. 31, 2018
Jun. 30, 2017
Mar. 31, 2018
Dec. 31, 2017
Feb. 18, 2016
Class of Stock [Line Items]          
Shares of common stock issued (in shares) 11,924,478   11,924,478 11,915,830  
Aggregate offering price of shelf registration         $ 600,000,000
Reinvestment of dividends paid to common stockholders $ 310,204        
Current availability under shelf registration $ 524,100,000   $ 524,100,000    
Series A Cumulative Redeemable Preferred Stock [Member]          
Class of Stock [Line Items]          
Preferred stock interest rate 7.375%        
Depositary Shares [Member]          
Class of Stock [Line Items]          
Shares outstanding 5,200,000   5,200,000    
Preferred Stock [Member]          
Class of Stock [Line Items]          
Shares outstanding 52,000   52,000    
Preferred Stock [Member] | Series A Cumulative Redeemable Preferred Stock [Member]          
Class of Stock [Line Items]          
Preferred stock interest rate 7.375%        
Dividend Reinvestment Plan [Member]          
Class of Stock [Line Items]          
Reinvestment of distributions to stockholders (in shares)     70,863    
Reinvestment of dividends paid to common stockholders     $ 2,100,000    
Underwritten Public Offering [Member] | Depositary Shares [Member]          
Class of Stock [Line Items]          
Reduction in shelf registration availability   $ 73,800,000