Annual report pursuant to Section 13 and 15(d)

FAIR VALUE (Details)

v3.19.3.a.u2
FAIR VALUE (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Fair Value    
Investments at fair value $ 87,250 $ 116,805
U.S. treasury bills    
Fair Value    
Investments at fair value 12,539  
Government-sponsored enterprises securities    
Fair Value    
Investments at fair value 19,017 7,872
Corporate bonds and commercial paper    
Fair Value    
Investments at fair value 55,694 108,933
Fair value measurements recurring | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 94,707 125,911
Fair value measurements recurring | Money market funds | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 7,457 9,106
Fair value measurements recurring | U.S. treasury bills | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 12,539  
Fair value measurements recurring | Government-sponsored enterprises securities | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 19,017 7,872
Fair value measurements recurring | Corporate bonds and commercial paper | Estimate Of Fair Value Fair Value Disclosure    
Fair Value    
Investments at fair value 55,694 108,933
Fair value measurements recurring | Fair value inputs Level 1    
Fair Value    
Investments at fair value 7,457 9,106
Fair value measurements recurring | Fair value inputs Level 1 | Money market funds    
Fair Value    
Investments at fair value 7,457 9,106
Fair value measurements recurring | Fair value inputs Level 2    
Fair Value    
Investments at fair value 87,250 116,805
Fair value measurements recurring | Fair value inputs Level 2 | U.S. treasury bills    
Fair Value    
Investments at fair value 12,539  
Fair value measurements recurring | Fair value inputs Level 2 | Government-sponsored enterprises securities    
Fair Value    
Investments at fair value 19,017 7,872
Fair value measurements recurring | Fair value inputs Level 2 | Corporate bonds and commercial paper    
Fair Value    
Investments at fair value $ 55,694 $ 108,933