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Supplementary Balance Sheet Detail (Schedule Of Analysis Of The 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 [Roll Forward]      
Balance at beginning of year $ 5,474 $ 1,129 $ 1,097
Additions 1,458 4,636 122
Deductions 715 291 90
Balance at end of year 8,243 5,474 $ 1,129
Cumulative Effect, Period of Adoption, Adjustment      
Allowance for Doubtful Accounts Receivable [Roll Forward]      
Balance at beginning of year $ 2,026    
Balance at end of year   $ 2,026