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Summary Of Significant Accounting Policies (Schedule Of Allowance For Doubtful Accounts) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance For Doubtful Accounts Receivable Rollforward      
Balance at Beginning of Period $ 10,085 $ 1,733 $ 105
Charges to Operations 2,160 10,323 1,718
Deductions (10,874) (1,971) (90)
Balance at End of Period $ 1,371 $ 10,085 $ 1,733