Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Assets:    
Investments in marketable securities $ 253,473 $ 254,099
Derivatives 18,856 13,557
Total assets 272,329  
Liabilities:    
Derivatives 1,010  
Level 1 [Member]    
Assets:    
Investments in marketable securities 3,955  
Derivatives 7,130  
Total assets 11,085  
Level 2 [Member]    
Assets:    
Investments in marketable securities 249,518  
Derivatives 2,456  
Total assets 251,974  
Liabilities:    
Derivatives 1,010  
Level 3 [Member]    
Assets:    
Derivatives 9,270  
Total assets 9,270  
Liabilities:    
Derivatives $ 0