Annual report pursuant to Section 13 and 15(d)

Short-Term And Long-Term Investments And Restricted Deposits (Contractual Maturities Of Short-Term And Long-Term Investments And Restricted Deposits) (Details)

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Short-Term And Long-Term Investments And Restricted Deposits (Contractual Maturities Of Short-Term And Long-Term Investments And Restricted Deposits) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Investments [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
One year or less, Amortized Cost $ 129,232 $ 21,141
One year through five years, Amortized Cost 406,140 464,270
Five years through ten years, Amortized Cost 34,945 39,732
Greater than ten years, Amortized Cost 56,720 81,860
Total, Amortized Cost 627,037 607,003
One year or less, Fair Value 130,499 21,346
One year through five years, Fair Value 413,953 474,255
Five years through ten years, Fair Value 34,961 39,731
Greater than ten years, Fair Value 57,226 81,893
Total, Fair Value 636,639 617,225
Restricted Deposits [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
One year or less, Amortized Cost 19,666 17,387
One year through five years, Amortized Cost 7,085 5,368
Five years through ten years, Amortized Cost     
Greater than ten years, Amortized Cost     
Total, Amortized Cost 26,751 22,755
One year or less, Fair Value 19,666 17,392
One year through five years, Fair Value 7,152 5,366
Five years through ten years, Fair Value     
Greater than ten years, Fair Value     
Total, Fair Value $ 26,818 $ 22,758