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Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Mar. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]        
Cost $ 7,535 $ 7,930    
Gross unrealized gain 6 0    
Gross unrealized loss (54) (58)    
Fair value, investments 7,487 7,872    
Less cash equivalents, Carrying amount 505 569 $ 1,631 $ 1,190
Money Market [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Cost 240 246    
Gross unrealized gain 0 0    
Gross unrealized loss 0 0    
Fair value, investments 240 246    
Commercial Paper [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Cost 199 247    
Gross unrealized gain 0 0    
Gross unrealized loss 0 0    
Fair value, investments 199 247    
Treasury Bills [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Cost 7,481 7,876    
Gross unrealized gain 6 0    
Gross unrealized loss 0 (4)    
Fair value, investments 7,487 7,872    
Equity Securities [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Cost 54 54    
Gross unrealized gain 0 0    
Gross unrealized loss (54) (54)    
Fair value, investments 0 0    
Debt and Equity Securities [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Cost 7,974 8,423    
Gross unrealized gain 6 0    
Gross unrealized loss (54) (58)    
Fair value, investments 7,926 8,365    
Less Cash and Cash Equivalents [Member]        
Schedule of Available-for-sale Securities [Line Items]        
Gross unrealized gain 0 0    
Gross unrealized loss 0 0    
Less cash equivalents, Carrying amount 439 493    
Less cash equivalents, Fair value $ 439 $ 493