Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Financial Instrument (Details)

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Summary of Significant Accounting Policies - Financial Instrument (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amount by which carrying value of fixed-rate long-term debt is less than its fair value $ 5,924  
Fair Value    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt value $ 363,460 $ 309,377