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 9 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2013
Mar. 31, 2012
Investments in an Unrealized Loss Position        
Fair Value $ 335,063,000   $ 335,063,000  
Gross Unrealized Losses, less than 12 months (397,000) [1]   (397,000) [1]  
Continuous loss position not exceeding this period 12 months      
Net realized securities gains (losses) 700,000 100,000 2,100,000 700,000
U.S. Treasury securities
        
Investments in an Unrealized Loss Position        
Fair Value 1,996,000   1,996,000  
Gross Unrealized Losses, less than 12 months (1,000) [1]   (1,000) [1]  
U.S. Government agency securities
        
Investments in an Unrealized Loss Position        
Fair Value 63,513,000   63,513,000  
Gross Unrealized Losses, less than 12 months (6,000) [1]   (6,000) [1]  
Municipal securities
        
Investments in an Unrealized Loss Position        
Fair Value 29,376,000   29,376,000  
Gross Unrealized Losses, less than 12 months (62,000) [1]   (62,000) [1]  
Corporate debt securities
        
Investments in an Unrealized Loss Position        
Fair Value 232,589,000   232,589,000  
Gross Unrealized Losses, less than 12 months (321,000) [1]   (321,000) [1]  
Sovereign securities
        
Investments in an Unrealized Loss Position        
Fair Value 7,589,000   7,589,000  
Gross Unrealized Losses, less than 12 months $ (7,000) [1]   $ (7,000) [1]  
[1] Of the total gross unrealized losses, there were no amounts that, as of March 31, 2013, had been in a continuous loss position for 12 months or more.