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Revenue From Contracts With Customers (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Concentration Risk [Line Items]      
Revenue recognized that was included in the contract liability balance at the beginning of the period $ 30,378 $ 14,995  
One Customer | Customer Concentration Risk | Accounts Receivable      
Concentration Risk [Line Items]      
Concentration risk, percentage 22.00%   21.00%