Quarterly report pursuant to Section 13 or 15(d)

Fair value measurements (Details)

v3.10.0.1
Fair value measurements (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Marketable securities:    
Available-for-sale securities, Debt Securities, Current, Total $ 84,652 $ 124,218
Recurring basis    
Marketable securities:    
Corporate debt securities 82,668  
Commercial paper 1,984  
Available-for-sale securities, Debt Securities, Current, Total 84,652  
Recurring basis | Level 1    
Marketable securities:    
Corporate debt securities 82,668  
Available-for-sale securities, Debt Securities, Current, Total 82,668  
Recurring basis | Level 2    
Marketable securities:    
Commercial paper 1,984  
Available-for-sale securities, Debt Securities, Current, Total $ 1,984