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Investments And Fair Value Measurements (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2011
years
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2008
Investments And Fair Value Measurements [Line items]        
Cash and cash equivalents $ 375,441,000 $ 324,188,000 $ 331,098,000 $ 165,669,000
Long term investment, contractual maturity period, low, years 1      
Long term investment, contractual maturity period, high, years 2      
Cost of investment in private company 2,000,000 2,500,000    
Write-down of corporate preferred equity securities   6,500,000    
Realized (loss) on investment portfolio   (5,700,000)    
Realized gain on investment portfolio, new cost basis   800,000    
Impairment charges related to private company investments 0      
US Treasury and other government agencies percentage of available-for-sale securities 54.00%      
Corporate bonds percentage of available-for-sale securities 29.00%      
Commercial paper percentage of available-for-sale securities 7.00%      
Non-US government securities percentage of available-for-sale securities 3.00%      
Money market funds percentage of available-for-sale securities 7.00%      
Cash equivalents included in available-for-sale securities 41,400,000      
United States [Member]
       
Investments And Fair Value Measurements [Line items]        
Cash equivalents and investments 151,400,000      
Foreign Country [Member]
       
Investments And Fair Value Measurements [Line items]        
Cash equivalents and investments $ 440,200,000