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Debt - Additional Information (Details)
12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Nov. 05, 2012
USD ($)
Debt Instrument [Line Items]      
Maximum borrowing availability under revolving credit facility (up to for $175,000) $ 250,000,000   $ 175,000,000
Adjusted funds from operations (in percentage) 95.00%    
Outstanding borrowing under the revolving credit facility $ 32,000,000 $ 52,500,000  
Consolidated fixed charge coverage ratio (in percentage) 3.2    
Fixed charge coverage ratio (in percentage) 1.5    
Fixed Rate Debt      
Debt Instrument [Line Items]      
Estimated fair value of debt $ 506,600,000 516,000,000  
Variable rate debt      
Debt Instrument [Line Items]      
Estimated fair value of debt 32,000,000 52,500,000  
Senior Secured Revolving Credit Facility      
Debt Instrument [Line Items]      
Maximum borrowing availability under revolving credit facility (up to for $175,000) 250,000,000    
Outstanding borrowing under the revolving credit facility $ 32,000,000 $ 52,500,000