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Debt And Interest Expense (Carrying Amounts Of Liability And Equity Components) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Aug. 15, 2007
Debt Disclosure [Abstract]      
Carrying amount of equity component (net of issuance costs of $14,449) $ 418,996 $ 418,996  
Principal amount of convertible debentures 1,250,000 1,250,000 1,250,000
Unamortized discount of liability component (663,588) (671,539)  
Carrying amount of liability component 586,412 578,461  
Contingent interest derivative 11,202 11,625  
Convertible debentures, including contingent interest derivative $ 597,614 $ 590,086