Quarterly report pursuant to Section 13 or 15(d)

Cash, Cash Equivalents and Available-For-Sale Securities (Details)

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Cash, Cash Equivalents and Available-For-Sale Securities (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Sep. 30, 2013
Dec. 31, 2012
Cash, cash equivalents and available-for-sale securities        
Cash and cash equivalents $ 12,814 $ 20,854 $ 16,031 $ 33,484
Available-for-sale securities 144,858 191,121    
Cash, cash equivalents and available-for-sale securities 157,672 211,975    
Money Market Funds [Member]
       
Cash, cash equivalents and available-for-sale securities        
Cash, cash equivalents and available-for-sale securities 8,754 9,059    
U S Treasury Securities [Member]
       
Cash, cash equivalents and available-for-sale securities        
Investments at fair value 2,029 2,085    
U S Government Sponsored Enterprises Debt Securities [Member]
       
Cash, cash equivalents and available-for-sale securities        
Investments at fair value 52,093 67,178    
Corporate Bond Securities And Commercial Paper [Member]
       
Cash, cash equivalents and available-for-sale securities        
Investments at fair value 94,036 133,458    
Demand Deposits [Member]
       
Cash, cash equivalents and available-for-sale securities        
Cash, cash equivalents and available-for-sale securities $ 760 $ 195