Quarterly report pursuant to Section 13 or 15(d)

Fair Value (Details)

v2.4.0.8
Fair Value (Details) (Recurring basis, USD $)
In Thousands, unless otherwise specified
Jun. 30, 2013
Dec. 31, 2012
Level 1
   
Fair Value    
Investments at fair value $ 7,688 $ 23,936
Level 1 | Money market funds
   
Fair Value    
Investments at fair value 7,688 23,936
Level 2
   
Fair Value    
Investments at fair value 243,672 274,054
Level 2 | Government-sponsored enterprise securities
   
Fair Value    
Investments at fair value 92,470 77,047
Level 2 | Corporate bonds and commercial paper
   
Fair Value    
Investments at fair value 151,202 197,007
Total
   
Fair Value    
Investments at fair value 251,360 297,990
Total | Money market funds
   
Fair Value    
Investments at fair value 7,688 23,936
Total | Government-sponsored enterprise securities
   
Fair Value    
Investments at fair value 92,470 77,047
Total | Corporate bonds and commercial paper
   
Fair Value    
Investments at fair value $ 151,202 $ 197,007