Quarterly report pursuant to Section 13 or 15(d)

Fair Value (Details)

v3.19.2
Fair Value (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Fair Value    
Investments at fair value $ 100,224 $ 116,805
Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 110,079 125,911
Government-sponsored enterprises securities    
Fair Value    
Investments at fair value 4,997 7,872
Corporate bonds and commercial paper    
Fair Value    
Investments at fair value 95,227 108,933
Fair value inputs Level 1    
Fair Value    
Investments at fair value 9,855 9,106
Fair value inputs Level 2    
Fair Value    
Investments at fair value 100,224 116,805
Fair value measurements recurring | Money market funds | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 9,855 9,106
Fair value measurements recurring | Government-sponsored enterprises securities | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 4,997 7,872
Fair value measurements recurring | Corporate bonds and commercial paper | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 95,227 108,933
Fair value measurements recurring | Fair value inputs Level 1 | Money market funds    
Fair Value    
Investments at fair value 9,855 9,106
Fair value measurements recurring | Fair value inputs Level 2 | Government-sponsored enterprises securities    
Fair Value    
Investments at fair value 4,997 7,872
Fair value measurements recurring | Fair value inputs Level 2 | Corporate bonds and commercial paper    
Fair Value    
Investments at fair value $ 95,227 $ 108,933