Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.19.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Assets measured at fair value on a recurring basis:    
Marketable securities $ 75,866 $ 99,679
U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities 53,737 49,793
Cash and money market funds    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 22,129 34,886
Overnight repurchase agreements    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents   15,000
Recurring    
Assets measured at fair value on a recurring basis:    
Total 75,866 99,679
Recurring | U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities 53,737 49,793
Recurring | Level 1    
Assets measured at fair value on a recurring basis:    
Total 75,866 84,679
Recurring | Level 1 | U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities 53,737 49,793
Recurring | Level 2    
Assets measured at fair value on a recurring basis:    
Total   15,000
Recurring | Cash and money market funds    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 22,129 34,886
Recurring | Cash and money market funds | Level 1    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents $ 22,129 34,886
Recurring | Overnight repurchase agreements    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents   15,000
Recurring | Overnight repurchase agreements | Level 2    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents   $ 15,000