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Revenue - Receivables (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Total customer receivables $ 339,923 $ 288,288
Unbilled receivables 13,616 14,752
Billed receivables    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Total customer receivables $ 326,307 $ 273,536