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Long-Term Debt - Summary (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Sep. 30, 2020
Aug. 26, 2020
Debt Instrument [Line Items]        
Total long-term debt $ 739,499 $ 615,916 $ 532,775  
Deferred finance costs, net 6,500 7,100 7,200  
Revolving unsecured credit facility, maturing 2024 | Line of Credit        
Debt Instrument [Line Items]        
Total long-term debt $ 246,000 123,000 40,000  
4.625% senior unsecured notes due 2028 | Senior Notes        
Debt Instrument [Line Items]        
Stated interest rate (as a percent) 4.625%     4.625%
Total long-term debt $ 493,499 $ 492,916 $ 492,775