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Available-For-Sale Securities (Summary Of The Classification Of Available-For-Sale Debt And Equity Securities) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Investments, Debt and Equity Securities [Abstract]    
Cash and cash equivalents $ 518,248 $ 9,000,954
Short-term marketable securities 0 16,491
Long-term marketable securities 48,168 63,704
Estimated Fair Value, Total $ 566,416 $ 9,081,149