Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value and Carrying Value of Significant Fixed Rate Long-Term Debt (Details)

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Fair Value Measurements - Fair Value and Carrying Value of Significant Fixed Rate Long-Term Debt (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Mar. 10, 2017
May 09, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Carrying Value $ 970,914 $ 1,024,703    
Mortgage Notes        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair Value 233,373 203,031    
Carrying Value 229,828 199,972    
Other        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair Value 3,602 3,760    
Carrying Value 3,771 3,947    
5.0% Notes        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair Value 276,979 279,148    
Carrying Value $ 289,273 289,273    
Stated interest rate on debt agreement 5.00%     5.00%
6.125% Notes        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair Value $ 235,625 248,750    
Carrying Value $ 250,000 $ 250,000    
Stated interest rate on debt agreement 6.125%   6.125%