Quarterly report pursuant to Section 13 or 15(d)

Marketable Securities (Continuous Unrealized Loss Position) (Details)

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Marketable Securities (Continuous Unrealized Loss Position) (Details) (USD $)
 3 Months Ended 6 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2011
Dec. 31, 2010
Investments in an Unrealized Loss Position        
Fair Value $ 465,442,000   $ 465,442,000  
Gross Unrealized Losses, less than 12 months (1,561,000) [1]   (1,561,000) [1]  
Gross Unrealized Losses, 12 Months or Longer 0   0  
Net realized securities gains (losses) (100,000) 400,000 600,000 1,500,000
Months in Loss Position Not Exceeding this Period 12      
Securities Maximum Maturity (years) 3   3  
U.S. Treasury securities
        
Investments in an Unrealized Loss Position        
Fair Value 23,995,000   23,995,000  
Gross Unrealized Losses, less than 12 months (3,000) [1]   (3,000) [1]  
Gross Unrealized Losses, 12 Months or Longer 0   0  
U.S. Government agency securities
        
Investments in an Unrealized Loss Position        
Fair Value 209,146,000   209,146,000  
Gross Unrealized Losses, less than 12 months (299,000) [1]   (299,000) [1]  
Gross Unrealized Losses, 12 Months or Longer 0   0  
Municipal securities
        
Investments in an Unrealized Loss Position        
Fair Value 3,626,000   3,626,000  
Gross Unrealized Losses, less than 12 months (1,000) [1]   (1,000) [1]  
Gross Unrealized Losses, 12 Months or Longer 0   0  
Corporate debt securities
        
Investments in an Unrealized Loss Position        
Fair Value 214,565,000   214,565,000  
Gross Unrealized Losses, less than 12 months (1,199,000) [1]   (1,199,000) [1]  
Gross Unrealized Losses, 12 Months or Longer 0   0  
Sovereign securities
        
Investments in an Unrealized Loss Position        
Fair Value 14,110,000   14,110,000  
Gross Unrealized Losses, less than 12 months (59,000) [1]   (59,000) [1]  
Gross Unrealized Losses, 12 Months or Longer $ 0   $ 0  
[1] Of the total gross unrealized losses, there were no amounts that, as of December 31, 2011, had been in a continuous loss position for 12 months or more.