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Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($)
$ in Thousands
Mar. 31, 2022
Dec. 31, 2021
Mar. 31, 2021
Dec. 31, 2020
Investments        
Cost $ 2,053 $ 3,054    
Gross unrealized gain 3 2    
Gross unrealized loss 0 0    
Fair value, investments 2,056 3,056    
Cash equivalents, Carrying amount 7,604 6,713 $ 1,045 $ 1,090
Commercial Paper [Member]        
Investments        
Cost 1,324 1,520    
Gross unrealized gain 0 0    
Gross unrealized loss 0 0    
Fair value, investments 1,324 1,520    
Treasury Bills [Member]        
Investments        
Cost 7,996 8,000    
Gross unrealized gain 1 0    
Gross unrealized loss 0 0    
Fair value, investments 7,997 8,000    
Equity Securities [Member]        
Investments        
Cost 54 54    
Gross unrealized gain 2 2    
Gross unrealized loss 0 0    
Fair value, investments 56 56    
Debt and Equity Securities [Member]        
Investments        
Cost 9,374 9,574    
Gross unrealized gain 3 2    
Gross unrealized loss 0 0    
Fair value, investments 9,377 9,576    
Less Cash Equivalents [Member]        
Investments        
Gross unrealized gain 0 0    
Gross unrealized loss 0 0    
Cash equivalents, Carrying amount 7,321 6,520    
Cash equivalents, Fair value $ 7,321 $ 6,520