Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details)

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Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents $ 200,218 $ 184,620 $ 377,205 $ 164,798
Cash equivalents 125,800 98,000    
Domestic Bank Accounts        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 170,128 156,122    
Foreign Bank Accounts        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 30,090 28,498    
Domestic Joint Ventures        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 4,091 7,714    
Foreign Joint Ventures        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 3,780 3,973    
Investments in Joint Ventures        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 7,871 11,687    
Captive Insurance Company        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 131,839 85,014    
Cash Not Held by Joint Ventures        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents $ 60,508 $ 87,919