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Cash Equivalents (Summary Of Cash Equivalents And Restricted Securities) (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2022
Dec. 31, 2021
Mar. 31, 2021
Dec. 31, 2020
Cash and Cash Equivalents [Line Items]        
Cash Equivalents, Cost Basis $ 51,408 $ 55,010 $ 57,102 $ 61,958
Cost Basis 10,018 10,015    
Unrealized Holding Gains    
Estimated Market Value 10,018 10,015    
Money Market Funds [Member]        
Cash and Cash Equivalents [Line Items]        
Cash Equivalents, Cost Basis 10,018 10,015    
Unrealized Holding Gains    
Cash Equivalents, Estimated Market Value $ 10,018 $ 10,015