Quarterly report pursuant to Section 13 or 15(d)

Fair Value (Details)

v3.5.0.2
Fair Value (Details) - USD ($)
$ in Thousands
Jun. 30, 2016
Dec. 31, 2015
Fair Value    
Investments at fair value $ 77,143 $ 97,867
Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 92,560 124,158
U S Treasury Securities    
Fair Value    
Investments at fair value 8,314 9,048
U S Government-Sponsored Enterprises Securities    
Fair Value    
Investments at fair value 20,684 48,613
Corporate Bonds And Commercial Paper    
Fair Value    
Investments at fair value 48,145 40,206
Fair Value Inputs Level1    
Fair Value    
Investments at fair value 15,417 26,291
Fair Value Inputs Level2    
Fair Value    
Investments at fair value 77,143 97,867
Fair Value Measurements Recurring | Money Market Funds | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 15,417 26,291
Fair Value Measurements Recurring | U S Treasury Securities | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 8,314 9,048
Fair Value Measurements Recurring | U S Government-Sponsored Enterprises Securities | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 20,684 48,613
Fair Value Measurements Recurring | Corporate Bonds And Commercial Paper | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 48,145 40,206
Fair Value Measurements Recurring | Fair Value Inputs Level1 | Money Market Funds    
Fair Value    
Investments at fair value 15,417 26,291
Fair Value Measurements Recurring | Fair Value Inputs Level2 | U S Treasury Securities    
Fair Value    
Investments at fair value 8,314 9,048
Fair Value Measurements Recurring | Fair Value Inputs Level2 | U S Government-Sponsored Enterprises Securities    
Fair Value    
Investments at fair value 20,684 48,613
Fair Value Measurements Recurring | Fair Value Inputs Level2 | Corporate Bonds And Commercial Paper    
Fair Value    
Investments at fair value $ 48,145 $ 40,206